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Moved page from wikipedia:en:Network topology (history)
此词条暂由彩云小译翻译，翻译字数共4801，未经人工整理和审校，带来阅读不便，请见谅。
{{short description|Arrangement of the elements of a communication network}}
{{about|the topology of communication networks|the topology of electrical networks|Topology (electrical circuits)|the topology of transport networks|Transport topology}}
{{Network Science}}
'''Network topology''' is the arrangement of the elements ([[Data link|links]], [[Node (networking)|nodes]], etc.) of a communication network.<ref name="Groth">{{Cite book
|last =Groth
|first = David
|author2=Toby Skandier
|title = Network+ Study Guide, Fourth Edition
|publisher = Sybex, Inc.
|year = 2005
|isbn = 0-7821-4406-3
}}</ref><ref name="atis">{{Cite web|author=ATIS committee PRQC|title=mesh topology|url=http://www.atis.org/glossary/definition.aspx?id=3516|url-status=dead|archive-url=http://archive.today/2013.04.14-061003/http://www.atis.org/glossary/definition.aspx?id=3516|archive-date=April 14, 2013|access-date=2008-10-10|work=ATIS Telecom Glossary 2007|publisher=[[Alliance for Telecommunications Industry Solutions]]}}</ref> Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including [[command and control]] radio networks,<ref name="GrantC2"/> industrial [[Fieldbus|fieldbusses]] and [[computer networks]].
Network topology is the arrangement of the elements (links, nodes, etc.) of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.
网络拓扑是元素(链接、节点等)的排列通讯网络。网络拓扑可用以界定或描述各类电讯网络的布局，包括指挥及控制无线电网络、工业现场总线及电脑网络。
Network topology is the [[topological]]<ref name="Chiang04">{{cite journal|last1=Chiang|first1=Mung|last2=Yang|first2=Michael|year=2004|title=Towards Network X-ities From a Topological Point of View: Evolvability and Scalability|url=http://www.cs.unm.edu/~karlinjf/papers/allerton.pdf|url-status=dead|journal=Proc. 42nd Allerton Conference|archive-url=https://web.archive.org/web/20130921053241/http://www.cs.unm.edu/~karlinjf/papers/allerton.pdf|archive-date=September 21, 2013}}</ref> structure of a network and may be depicted physically or logically. It is an application of [[graph theory]]<ref name="GrantC2">{{cite book|title=Network Topology in Command and Control |editor= Grant, T. J. |series= Advances in Information Security, Privacy, and Ethics |publisher= IGI Global |year= 2014 |url= https://books.google.com/books?id=zBOXBQAAQBAJ |pages= xvii, 228, 250 |isbn= 9781466660595 }}</ref> wherein communicating devices are modeled as nodes and the connections between the devices are modeled as links or lines between the nodes. '''Physical topology''' is the placement of the various components of a network (e.g., device location and cable installation), while '''logical topology''' illustrates how data flows within a network. Distances between nodes, physical interconnections, [[Bit rate|transmission rates]], or signal types may differ between two different networks, yet their logical topologies may be identical. A network’s physical topology is a particular concern of the [[physical layer]] of the [[OSI model]].
Network topology is the topological structure of a network and may be depicted physically or logically. It is an application of graph theory wherein communicating devices are modeled as nodes and the connections between the devices are modeled as links or lines between the nodes. Physical topology is the placement of the various components of a network (e.g., device location and cable installation), while logical topology illustrates how data flows within a network. Distances between nodes, physical interconnections, transmission rates, or signal types may differ between two different networks, yet their logical topologies may be identical. A network’s physical topology is a particular concern of the physical layer of the OSI model.
网络拓扑是网络的拓扑结构，可以在物理上或逻辑上描述。它是图论的一个应用，其中通信设备被建模为节点，设备之间的连接被建模为节点之间的链接或线。物理拓扑是放置网络的各种组件(例如，设备位置和电缆安装) ，而逻辑拓扑说明了数据如何在网络中流动。节点之间的距离、物理互连、传输速率或信号类型在两个不同的网络之间可能不同，但它们的逻辑拓扑可能是相同的。网络的物理拓扑结构是 OSI 模型物理层特别关注的问题。
Examples of network topologies are found in [[local area network]]s ([[LAN]]), a common computer network installation. Any given node in the LAN has one or more physical links to other devices in the network; graphically mapping these links results in a geometric shape that can be used to describe the physical topology of the network. A wide variety of physical topologies have been used in LANs, including [[ring network|ring]], [[bus network|bus]], [[mesh network|mesh]] and [[star network|star]]. Conversely, mapping the [[Traffic flow (computer networking)|data flow]] between the components determines the logical topology of the network. In comparison, [[CAN bus|Controller Area Networks]], common in vehicles, are primarily distributed [[control system]] networks of one or more controllers interconnected with sensors and actuators over, invariably, a physical bus topology.
Examples of network topologies are found in local area networks (LAN), a common computer network installation. Any given node in the LAN has one or more physical links to other devices in the network; graphically mapping these links results in a geometric shape that can be used to describe the physical topology of the network. A wide variety of physical topologies have been used in LANs, including ring, bus, mesh and star. Conversely, mapping the data flow between the components determines the logical topology of the network. In comparison, Controller Area Networks, common in vehicles, are primarily distributed control system networks of one or more controllers interconnected with sensors and actuators over, invariably, a physical bus topology.
网络拓扑的示例可以在局域网(LAN)中找到，LAN 是一种常见的计算机网络安装。局域网中的任何给定节点都有一个或多个到网络中其他设备的物理链路; 通过图形化地映射这些链路，得到一个可用于描述网络物理拓扑结构的几何形状。各种各样的物理拓扑在局域网中得到了广泛的应用，包括环形、总线、网格和星形。相反，在组件之间映射数据流决定了网络的逻辑拓扑。相比之下，车辆中常见的控制器区域网络主要是由一个或多个控制器组成的管理系统网络，这些控制器通过物理总线拓扑结构与传感器和执行器相互连接。
==Topologies==
[[File:NetworkTopologies.svg|right|thumb|300px|Diagram of different network topologies.]]
right|thumb|300px|Diagram of different network topologies.
= = 拓扑 = = 右图 | 300px | 不同网络拓扑图。
Two basic categories of network topologies exist, physical topologies and logical topologies.<ref name="Inc, S. 2002">Inc, S., (2002) . Networking Complete. Third Edition. San Francisco: Sybex</ref>
Two basic categories of network topologies exist, physical topologies and logical topologies.Inc, S., (2002) . Networking Complete. Third Edition. San Francisco: Sybex
存在两种基本的网络拓扑，即物理拓扑和逻辑拓扑。网络完成。第三版。旧金山: Sybex
The [[transmission medium]] layout used to link devices is the physical topology of the network. For conductive or fiber optical mediums, this refers to the layout of [[Structured cabling|cabling]], the locations of nodes, and the links between the nodes and the cabling.<ref name="Groth"/> The physical topology of a network is determined by the capabilities of the network access devices and media, the level of control or fault tolerance desired, and the cost associated with cabling or telecommunication circuits.
The transmission medium layout used to link devices is the physical topology of the network. For conductive or fiber optical mediums, this refers to the layout of cabling, the locations of nodes, and the links between the nodes and the cabling. The physical topology of a network is determined by the capabilities of the network access devices and media, the level of control or fault tolerance desired, and the cost associated with cabling or telecommunication circuits.
用于连接设备的介质布局是网络的物理拓扑结构。对于导电或光纤介质，这是指布线的布局，节点的位置，以及节点和布线之间的链接。网络的物理拓扑结构取决于网络接入设备和介质的能力、所需的控制或容错水平以及与布线或电信电路相关的成本。
In contrast, logical topology is the way that the signals act on the network media,<ref>{{citation |url=http://www.webopedia.com/quick_ref/topologies.asp |title=What Are Network Topologies? |access-date=2016-09-17}}</ref> or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices.<ref>{{Cite journal |author1=Leonardi, E. |author2=Mellia, M. |author3= Marsan, M. A. |date=2000 |title=Algorithms for the Logical Topology Design in WDM All-Optical Networks |url=https://www.researchgate.net/publication/2414623 |journal=Optical Networks Magazine |pages=35–46}}</ref> A network's logical topology is not necessarily the same as its physical topology. For example, the original [[twisted pair Ethernet]] using [[repeater hub]]s was a logical bus topology carried on a physical star topology. [[Token Ring]] is a logical ring topology, but is wired as a physical star from the [[media access unit]]. Physically, [[Avionics Full-Duplex Switched Ethernet|AFDX]] can be a cascaded star topology of multiple dual redundant Ethernet switches; however, the AFDX [[Avionics Full-Duplex Switched Ethernet#Virtual links|Virtual links]] are modeled as [[Time-division multiplexing|time-switched]] single-transmitter bus connections, thus following the safety model of a [[ARINC 429|single-transmitter bus topology]] previously used in aircraft. Logical topologies are often closely associated with [[media access control]] methods and protocols. Some networks are able to dynamically change their logical topology through configuration changes to their [[Router (computing)|router]]s and switches.
In contrast, logical topology is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices. A network's logical topology is not necessarily the same as its physical topology. For example, the original twisted pair Ethernet using repeater hubs was a logical bus topology carried on a physical star topology. Token Ring is a logical ring topology, but is wired as a physical star from the media access unit. Physically, AFDX can be a cascaded star topology of multiple dual redundant Ethernet switches; however, the AFDX Virtual links are modeled as time-switched single-transmitter bus connections, thus following the safety model of a single-transmitter bus topology previously used in aircraft. Logical topologies are often closely associated with media access control methods and protocols. Some networks are able to dynamically change their logical topology through configuration changes to their routers and switches.
相比之下，逻辑拓扑是信号作用于网络媒体的方式，或者是数据从一个设备通过网络传递到下一个设备的方式，而不考虑设备之间的物理互连。网络的逻辑拓扑不一定与其物理拓扑相同。例如，使用中继器集线器的原始双绞线以太网是在物理星型拓扑上进行的逻辑总线拓扑。令牌环是一个逻辑环拓扑，但是从媒体访问单元以物理星形连接。在物理上，AFDX 可以是多个双冗余以太网交换机的级联星型拓扑; 然而，AFDX 虚拟链路被建模为时间交换的单发射机总线连接，因此遵循了以前在飞机上使用的单发射机总线拓扑的安全模型。逻辑拓扑通常与媒体访问控制方法和协议密切相关。有些网络能够通过改变其路由器和交换机的配置来动态改变其逻辑拓扑结构。
==Links==
{{further|data transmission}}
The transmission media (often referred to in the literature as the ''physical media'') used to link devices to form a computer network include [[electrical cables]] ([[Ethernet]], [[HomePNA]], [[power line communication]], [[G.hn]]), [[optical fiber]] ([[fiber-optic communication]]), and [[radio waves]] ([[wireless networking]]). In the [[OSI model]], these are defined at layers 1 and 2 — the physical layer and the data link layer.
The transmission media (often referred to in the literature as the physical media) used to link devices to form a computer network include electrical cables (Ethernet, HomePNA, power line communication, G.hn), optical fiber (fiber-optic communication), and radio waves (wireless networking). In the OSI model, these are defined at layers 1 and 2 — the physical layer and the data link layer.
用于连接设备形成计算机网络的传输媒介(通常在文献中称为物理媒介)包括电缆(以太网、 HomepNA、电力线通信、 G.hn)、光纤(光纤通讯)和无线电波(无线网络)。在 OSI 模型中，这些定义在第1层和第2层ーー物理层和数据链路层。
A widely adopted ''family'' of transmission media used in local area network ([[LAN]]) technology is collectively known as [[Ethernet]]. The media and protocol standards that enable communication between networked devices over Ethernet are defined by [[IEEE 802.3]]. Ethernet transmits data over both copper and fiber cables. Wireless LAN standards (e.g. those defined by [[IEEE 802.11]]) use [[radio waves]], or others use [[IrDA|infrared]] signals as a transmission medium. [[Power line communication]] uses a building's power cabling to transmit data.
A widely adopted family of transmission media used in local area network (LAN) technology is collectively known as Ethernet. The media and protocol standards that enable communication between networked devices over Ethernet are defined by IEEE 802.3. Ethernet transmits data over both copper and fiber cables. Wireless LAN standards (e.g. those defined by IEEE 802.11) use radio waves, or others use infrared signals as a transmission medium. Power line communication uses a building's power cabling to transmit data.
局域网(LAN)技术中广泛采用的传输媒体系统统称为以太网。IEEE 802.3定义了支持网络设备通过以太网进行通信的媒体和协议标准。以太网通过铜缆和光缆传输数据。无线局域网标准(例如:。IEEE 802.11)定义的介质使用无线电波，或者使用红外线信号。电力线通信使用建筑物的电力电缆传输数据。
===Wired technologies===
[[File:Fibreoptic.jpg|thumb|upright=0.7|alt=Bundle of glass threads with light emitting from the ends|[[Fiber optic cables]] are used to transmit light from one computer/network node to another]]
The orders of the following wired technologies are, roughly, from slowest to fastest transmission speed.
The orders of the following wired technologies are, roughly, from slowest to fastest transmission speed.
以下有线技术的顺序大致是从最慢到最快的传输速度。
*''[[Coaxial cable]]'' is widely used for cable television systems, office buildings, and other work-sites for local area networks. The cables consist of copper or aluminum wire surrounded by an insulating layer (typically a flexible material with a high dielectric constant), which itself is surrounded by a conductive layer. The insulation between the conductors helps maintain the characteristic impedance of the cable which can help improve its performance. Transmission speed ranges from 200 million bits per second to more than 500 million bits per second.
*''[[ITU-T]] [[G.hn]]'' technology uses existing [[home wiring]] ([[Ethernet over coax|coaxial cable]], phone lines and [[Power line communication|power lines]]) to create a high-speed (up to 1 Gigabit/s) local area network.
* ''[[Signal trace]]s'' on [[printed circuit board]]s are common for board-level serial communication, particularly between certain types integrated circuits, a common example being [[Serial Peripheral Interface Bus|SPI]].
*''[[Ribbon cable]]'' (untwisted and possibly unshielded) has been a cost-effective media for serial protocols, especially within metallic enclosures or rolled within copper braid or foil, over short distances, or at lower data rates. Several serial network protocols can be deployed without shielded or twisted pair cabling, that is, with "flat" or "ribbon" cable, or a hybrid flat/twisted ribbon cable, should [[Electromagnetic compatibility|EMC]], length, and [[Bandwidth (computing)|bandwidth]] constraints permit: [[RS-232]],<ref>[https://www.jameco.com/z/GCAR11-R-Cable-Serial-Male-To-Female-25L-4-DB25-M-DB25-28-AWG-300V-Gray_12408.html Cable Serial Male To Female 25L 4' DB25 M-DB25 28 AWG 300V Gray], Part no.: 12408, Jameco Electronics.</ref> [[RS-422]], [[RS-485]],<ref>AN-1057 [http://www.ti.com/lit/an/snla049b/snla049b.pdf Ten ways to bulletproof RS-485 Interfaces], [[Texas Instruments]], p. 5. </ref> [[CAN Bus|CAN]],<ref>[[CANopen]],[https://www.phoenixcontact.com/assets/downloads_ed/global/web_dwl_technical_info/CANopen.pdf CANopen DR-303 V1.0 Cabling and Connector Pin Assignment], [[CAN in Automation]], p. 10.</ref> [[IEEE-488|GPIB]], [[SCSI]],<ref>Advantech Co., Ltd., Cable 50-Pin SCSI Ribbon type # PCL-10152-3E ([[Mouser Electronics]] #923-PCL-10152-3E)</ref> etc.
*''[[Twisted pair]] wire'' is the most widely used medium for all telecommunication.{{cn|date=May 2021}} Twisted-pair cabling consist of copper wires that are twisted into pairs. Ordinary telephone wires consist of two insulated copper wires twisted into pairs. Computer network cabling (wired [[Ethernet]] as defined by [[IEEE 802.3]]) consists of 4 pairs of copper cabling that can be utilized for both voice and data transmission. The use of two wires twisted together helps to reduce [[crosstalk (electronics)|crosstalk]] and [[electromagnetic induction]]. The transmission speed ranges from 2 million bits per second to 10 billion bits per second. Twisted pair cabling comes in two forms: unshielded twisted pair (UTP) and shielded twisted-pair (STP). Each form comes in several category ratings, designed for use in various scenarios.
*Coaxial cable is widely used for cable television systems, office buildings, and other work-sites for local area networks. The cables consist of copper or aluminum wire surrounded by an insulating layer (typically a flexible material with a high dielectric constant), which itself is surrounded by a conductive layer. The insulation between the conductors helps maintain the characteristic impedance of the cable which can help improve its performance. Transmission speed ranges from 200 million bits per second to more than 500 million bits per second.
*ITU-T G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network.
* Signal traces on printed circuit boards are common for board-level serial communication, particularly between certain types integrated circuits, a common example being SPI.
*Ribbon cable (untwisted and possibly unshielded) has been a cost-effective media for serial protocols, especially within metallic enclosures or rolled within copper braid or foil, over short distances, or at lower data rates. Several serial network protocols can be deployed without shielded or twisted pair cabling, that is, with "flat" or "ribbon" cable, or a hybrid flat/twisted ribbon cable, should EMC, length, and bandwidth constraints permit: RS-232,Cable Serial Male To Female 25L 4' DB25 M-DB25 28 AWG 300V Gray, Part no.: 12408, Jameco Electronics. RS-422, RS-485,AN-1057 Ten ways to bulletproof RS-485 Interfaces, Texas Instruments, p. 5. CAN,CANopen,CANopen DR-303 V1.0 Cabling and Connector Pin Assignment, CAN in Automation, p. 10. GPIB, SCSI,Advantech Co., Ltd., Cable 50-Pin SCSI Ribbon type # PCL-10152-3E (Mouser Electronics #923-PCL-10152-3E) etc.
*Twisted pair wire is the most widely used medium for all telecommunication. Twisted-pair cabling consist of copper wires that are twisted into pairs. Ordinary telephone wires consist of two insulated copper wires twisted into pairs. Computer network cabling (wired Ethernet as defined by IEEE 802.3) consists of 4 pairs of copper cabling that can be utilized for both voice and data transmission. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. The transmission speed ranges from 2 million bits per second to 10 billion bits per second. Twisted pair cabling comes in two forms: unshielded twisted pair (UTP) and shielded twisted-pair (STP). Each form comes in several category ratings, designed for use in various scenarios.
* 同轴电缆广泛用于有线电视系统、办公大楼和其他局域网工作场所。电缆由铜线或铝线组成，周围有一个绝缘层(通常是一种具有高介电常数的柔性材料) ，它本身被一个导电层包围。导体之间的绝缘有助于维持电缆的特性阻抗，从而有助于改善其性能。传输速度从每秒2亿比特到每秒5亿比特不等。
* ITU-T G.hn 技术利用现有的家庭布线(同轴电缆、电话线和电力线)创建高速(高达1Gigabit/s)的局域网。
* 印刷电路板上的信号痕迹在板级串行通信中很常见，特别是在某些类型的集成电路之间，一个常见的例子是 SPI。
* 带状电缆(未缠绕和可能未屏蔽)已成为串行协议的一种具有成本效益的介质，特别是在金属外壳内或在铜编织物或箔内轧制，短距离或以较低的数据速率。在电磁兼容、长度和带宽限制允许的情况下，可以部署几种串行网络协议，不需要屏蔽或双绞线缆，即使用“扁平”或“带状”电缆，或混合扁平/双绞带状电缆: RS-232，电缆串联男女25L 4’DB25 M-DB2528 AWG 300V Gray，Part No。翻译: 12408，Jameco Electronics Jameco Electronics。RS-422，RS-485，AN-1057防弹 RS-485接口的十种方法，德州仪器，第5页。CAN，CANopen，CANopen DR-303 V1.0布线和连接器插脚分配，CAN 在自动化，第10页。GPIB，SCSI，Advantech Co. ，Ltd. ，Cable 50-Pin SCSI 丝带型号 # PCL-10152-3E (Mouser Electronics # 923-PCL-10152-3E)等。
* 双绞线是所有电信中使用最广泛的媒介。双绞线电缆由铜线绞成双绞线组成。普通电话线由两根绝缘铜线绞成对组成。计算机网络布线(IEEE 802.3定义的有线以太网)由4对铜线组成，可用于语音和数据传输。使用双绞线有助于减少串音和电磁感应。传输速度从每秒200万比特到每秒100亿比特不等。双绞线有两种形式: 无屏蔽双绞线(UTP)和屏蔽双绞线(STP)。每个表单都有几个分类评级，设计用于各种场景。
[[File:World map of submarine cables.png|thumb|alt=World map with red and blue lines|2007 map showing submarine optical fiber telecommunication cables around the world.]]
*An ''[[optical fiber]]'' is a glass fiber. It carries pulses of light that represent data. Some advantages of optical fibers over metal wires are very low transmission loss and immunity from electrical interference. Optical fibers can simultaneously carry multiple wavelengths of light, which greatly increases the rate that data can be sent, and helps enable data rates of up to trillions of bits per second. Optic fibers can be used for long runs of cable carrying very high data rates, and are used for [[undersea cables]] to interconnect continents.
thumb|alt=World map with red and blue lines|2007 map showing submarine optical fiber telecommunication cables around the world.
*An optical fiber is a glass fiber. It carries pulses of light that represent data. Some advantages of optical fibers over metal wires are very low transmission loss and immunity from electrical interference. Optical fibers can simultaneously carry multiple wavelengths of light, which greatly increases the rate that data can be sent, and helps enable data rates of up to trillions of bits per second. Optic fibers can be used for long runs of cable carrying very high data rates, and are used for undersea cables to interconnect continents.
红色和蓝色线条的世界地图 | 2007年世界海底光纤通信电缆地图。光纤就是玻璃纤维
* 。它携带代表数据的光脉冲。与金属线相比，光纤的一些优点是传输损耗非常低，而且不会受到电干扰。光纤可以同时携带多种波长的光，这大大提高了数据的传输速率，并有助于使数据传输速率达到每秒数万亿比特。光纤可以用于长距离的电缆传输非常高的数据速率，也可以用于海底电缆连接大陆。
Price is a main factor distinguishing wired- and wireless-technology options in a business. Wireless options command a price premium that can make purchasing wired computers, printers and other devices a financial benefit. Before making the decision to purchase hard-wired technology products, a review of the restrictions and limitations of the selections is necessary. Business and employee needs may override any cost considerations.<ref>[http://smallbusiness.chron.com/disadvantages-wired-technology-17833.html], The Disadvantages of Wired Technology, Laura Acevedo, Demand Media.</ref>
Price is a main factor distinguishing wired- and wireless-technology options in a business. Wireless options command a price premium that can make purchasing wired computers, printers and other devices a financial benefit. Before making the decision to purchase hard-wired technology products, a review of the restrictions and limitations of the selections is necessary. Business and employee needs may override any cost considerations., The Disadvantages of Wired Technology, Laura Acevedo, Demand Media.
价格是区分企业有线和无线技术选择的一个主要因素。无线选择命令价格溢价，可以使购买有线电脑，打印机和其他设备的经济利益。在决定购买硬连线技术产品之前，有必要审查选择的限制和局限性。企业和员工的需求可能会压倒任何成本考虑因素，《有线技术的缺点》 ，劳拉 · 阿塞维多，《需求媒体》。
===Wireless technologies===
[[File:Wireless network.jpg|thumb|right|alt=Black laptop with router in the background |Personal computers are very often connected to networks using wireless links]]
{{Main|Wireless network}}
*''Terrestrial [[microwave]]'' – Terrestrial microwave communication uses Earth-based transmitters and receivers resembling satellite dishes. Terrestrial microwaves are in the low gigahertz range, which limits all communications to line-of-sight. Relay stations are spaced approximately {{convert|50|km|mi|abbr=on|sigfig=1}} apart.
*''[[Communications satellite]]s'' – Satellites communicate via microwave radio waves, which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically in [[geostationary orbit]] {{convert|35786|km|mi|abbr=on}} above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals.
*''[[Cellular network|Cellular]] and PCS systems'' use several radio communications technologies. The systems divide the region covered into multiple geographic areas. Each area has a low-power transmitter or radio relay antenna device to relay calls from one area to the next area.
*''Radio and [[spread spectrum]] technologies'' – Wireless local area networks use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANs use spread spectrum technology to enable communication between multiple devices in a limited area. [[IEEE 802.11]] defines a common flavor of open-standards wireless radio-wave technology known as [[Wi-Fi]].
*''[[Free-space optical communication]]'' uses visible or invisible light for communications. In most cases, [[line-of-sight propagation]] is used, which limits the physical positioning of communicating devices.
thumb|right|alt=Black laptop with router in the background |Personal computers are very often connected to networks using wireless links
*Terrestrial microwave – Terrestrial microwave communication uses Earth-based transmitters and receivers resembling satellite dishes. Terrestrial microwaves are in the low gigahertz range, which limits all communications to line-of-sight. Relay stations are spaced approximately apart.
*Communications satellites – Satellites communicate via microwave radio waves, which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically in geostationary orbit above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals.
*Cellular and PCS systems use several radio communications technologies. The systems divide the region covered into multiple geographic areas. Each area has a low-power transmitter or radio relay antenna device to relay calls from one area to the next area.
*Radio and spread spectrum technologies – Wireless local area networks use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANs use spread spectrum technology to enable communication between multiple devices in a limited area. IEEE 802.11 defines a common flavor of open-standards wireless radio-wave technology known as Wi-Fi.
*Free-space optical communication uses visible or invisible light for communications. In most cases, line-of-sight propagation is used, which limits the physical positioning of communicating devices.
= = = 无线技术 = = = 拇指 | 右边 | ALT = 黑色笔记本电脑，后台有路由器 | 个人电脑经常使用无线链路连接到网络
* 地面微波-地面微波通信使用类似卫星天线的地面发射机和接收机。地球上的微波是在低千兆赫的范围内，这限制了所有通信的视线。中继站之间的间隔大致相同。
* 通信卫星——卫星通过微波无线电波进行通信，这种无线电波不会被地球大气层偏转。这些卫星位于太空，通常位于赤道上方的地球静止轨道。这些地球轨道系统能够接收和中继语音、数据和电视信号。
* 蜂窝和 PCS 系统使用多种无线电通信技术。这些系统将覆盖的区域划分为多个地理区域。每个区域都有一个低功率发射机或无线电中继天线装置，用于将呼叫从一个区域转移到下一个区域。
* 无线电和扩频技术——无线局域网使用类似于数字蜂窝和低频无线电技术的高频无线电技术。无线局域网使用扩频技术在有限的区域内实现多个设备之间的通信。IEEE 802.11定义了一种称为 Wi-Fi 的开放标准无线电波技术。
* 自由空间光通信系统使用可见光或不可见光进行通讯。在大多数情况下，使用的是视线传播，这限制了通信设备的物理定位。
===Exotic technologies===
There have been various attempts at transporting data over exotic media:
There have been various attempts at transporting data over exotic media:
= = 外来技术 = = = 已经有多种尝试通过外来媒体传输数据:
* [[IP over Avian Carriers]] was a humorous April fool's [[Request for Comments]], issued as '''RFC 1149'''. It was implemented in real life in 2001.<ref>{{cite web|url=http://www.blug.linux.no/rfc1149 |title=Bergen Linux User Group's CPIP Implementation |publisher=Blug.linux.no |access-date=2014-03-01}}</ref>
* Extending the Internet to interplanetary dimensions via radio waves, the [[Interplanetary Internet]].<ref>{{citation |url=http://www.ipnsig.org/reports/ISART9-2000.pdf |archive-url=https://web.archive.org/web/20120113053223/http://www.ipnsig.org/reports/ISART9-2000.pdf |archive-date=2012-01-13 |title=Interplanetary Internet |publisher=Third Annual International Symposium on Advanced Radio Technologies |author=A. Hooke |date=September 2000 |access-date=2011-11-12}}</ref>
* IP over Avian Carriers was a humorous April fool's Request for Comments, issued as RFC 1149. It was implemented in real life in 2001.
* Extending the Internet to interplanetary dimensions via radio waves, the Interplanetary Internet.
* 信鸽IP通讯是一份幽默的愚人节评论请求，发行号为 RFC 1149。它于2001年在现实生活中实施。
* 透过无线电波将互联网扩展至星际空间，星际互联网。
Both cases have a large [[round-trip delay time]], which gives slow two-way communication, but doesn't prevent sending large amounts of information.
Both cases have a large round-trip delay time, which gives slow two-way communication, but doesn't prevent sending large amounts of information.
这两种情况都有一个很大的来回通讯延迟，可以进行缓慢的双向通信，但并不妨碍发送大量信息。
==Nodes==
{{Main|Node (networking)}}
Network nodes are the points of connection of the transmission medium to transmitters and receivers of the electrical, optical, or radio signals carried in the medium. Nodes may be associated with a computer, but certain types may have only a microcontroller at a node or possibly no programmable device at all. In the simplest of serial arrangements, one [[RS-232]] transmitter can be connected by a pair of wires to one receiver, forming two nodes on one link, or a Point-to-Point topology. Some protocols permit a single node to only either transmit or receive (e.g., [[ARINC 429]]). Other protocols have nodes that can both transmit and receive into a single channel (e.g., [[CANbus|CAN]] can have many transceivers connected to a single bus). While the conventional [[Systems engineering|system]] building blocks of a [[computer network]] include [[network interface controller]]s (NICs), [[repeater]]s, [[Ethernet hub|hubs]], [[Network bridge|bridges]], [[Network switch|switches]], [[Router (computing)|routers]], [[modem]]s, [[Gateway (telecommunications)|gateways]], and [[Firewall (computing)|firewalls]], most address network concerns beyond the physical network topology and may be represented as single nodes on a particular physical network topology.
Network nodes are the points of connection of the transmission medium to transmitters and receivers of the electrical, optical, or radio signals carried in the medium. Nodes may be associated with a computer, but certain types may have only a microcontroller at a node or possibly no programmable device at all. In the simplest of serial arrangements, one RS-232 transmitter can be connected by a pair of wires to one receiver, forming two nodes on one link, or a Point-to-Point topology. Some protocols permit a single node to only either transmit or receive (e.g., ARINC 429). Other protocols have nodes that can both transmit and receive into a single channel (e.g., CAN can have many transceivers connected to a single bus). While the conventional system building blocks of a computer network include network interface controllers (NICs), repeaters, hubs, bridges, switches, routers, modems, gateways, and firewalls, most address network concerns beyond the physical network topology and may be represented as single nodes on a particular physical network topology.
网络节点是介质与媒体上所载的电子、光学或无线电信号的发射机和接收机的连接点。节点可能与计算机相关联，但某些类型的节点上可能只有一个微控制器，或者可能根本没有可编程设备。在最简单的串行安排中，一个 RS-232发射机可以通过一对导线连接到一个接收机，在一个链路上形成两个节点，或者点对点拓扑。有些协议允许单个节点只发送或接收(例如 ARINC 429)。其他协议的节点可以同时发送和接收到单个信道(例如，CAN 可以将许多收发信机连接到单个总线)。虽然传统的计算机网络系统构建模块包括网络接口控制器(NICs)、中继器、集线器、桥接器、交换机、路由器、调制解调器、网关和防火墙，但大多数解决的网络问题超出了物理网络拓扑，可以表示为特定物理网络拓扑上的单个节点。
<!-- The following headings of Computer networking equipment are now possibly partially depreciated in this article, having been copied from [[Computer network]]. While these are indeed computer network building blocks, most provide services above the Physical Layer. Some headings can be modified to be inclusive of non-internet or non-Ethernet technologies specifically to address how they are relevant to (e.g., repeaters have long use in serial protocols, USB depends on Hubs). -->
===Network interfaces===
[[File:ForeRunnerLE 25 ATM Network Interface (1).jpg|thumb|right|alt=A network interface circuit with port for ATM|An [[Asynchronous Transfer Mode|ATM]] network interface in the form of an accessory card. A lot of network interfaces are built-in.]]
A [[network interface controller]] (NIC) is [[computer hardware]] that provides a computer with the ability to access the transmission media, and has the ability to process low-level network information. For example, the NIC may have a connector for accepting a cable, or an aerial for wireless transmission and reception, and the associated circuitry.
A network interface controller (NIC) is computer hardware that provides a computer with the ability to access the transmission media, and has the ability to process low-level network information. For example, the NIC may have a connector for accepting a cable, or an aerial for wireless transmission and reception, and the associated circuitry.
网络接口网卡是一种计算机硬件，它为计算机提供访问传输媒体的能力，并且具有处理低级网络信息的能力。例如，NIC 可能具有用于接收电缆的连接器，或用于无线传输和接收的天线，以及相关的电路。
The NIC responds to traffic addressed to a [[network address]] for either the NIC or the computer as a whole.
The NIC responds to traffic addressed to a network address for either the NIC or the computer as a whole.
网卡对网络地址的流量作出响应，无论是网卡还是计算机作为一个整体。
In [[Ethernet]] networks, each network interface controller has a unique [[MAC address|Media Access Control]] (MAC) address—usually stored in the controller's permanent memory. To avoid address conflicts between network devices, the [[Institute of Electrical and Electronics Engineers]] (IEEE) maintains and administers MAC address uniqueness. The size of an Ethernet MAC address is six [[Octet (computing)|octets]]. The three most significant octets are reserved to identify NIC manufacturers. These manufacturers, using only their assigned prefixes, uniquely assign the three least-significant octets of every Ethernet interface they produce.
In Ethernet networks, each network interface controller has a unique Media Access Control (MAC) address—usually stored in the controller's permanent memory. To avoid address conflicts between network devices, the Institute of Electrical and Electronics Engineers (IEEE) maintains and administers MAC address uniqueness. The size of an Ethernet MAC address is six octets. The three most significant octets are reserved to identify NIC manufacturers. These manufacturers, using only their assigned prefixes, uniquely assign the three least-significant octets of every Ethernet interface they produce.
在以太网中，每个网卡都有一个独特的媒体访问控制(Media Access Control，MAC)地址ーー通常存储在控制器的永久存储器中。为了避免网络设备之间的地址冲突，电气和电子工程师协会(IEEE)维护和管理 MAC 地址唯一性。以太网 MAC 地址的大小是六个八位。三个最重要的八位字节被保留用于识别 NIC 制造商。这些制造商只使用它们分配的前缀，唯一地分配它们生产的每个以太网接口的三个最不重要的八位元组。
===Repeaters and hubs===
A [[repeater]] is an [[Electronics|electronic]] device that receives a network [[signal (information theory)|signal]], cleans it of unnecessary noise and regenerates it. The signal may be reformed or [[retransmission (data networks)|retransmitted]] at a higher power level, to the other side of an obstruction possibly using a different transmission medium<!-- technically bridge-to-bridge -->, so that the signal can cover longer distances without degradation. Commercial repeaters have extended [[RS-232]] segments from 15 meters to over a kilometer.<ref>U.S. Converters, [http://www.usconverters.com/rs232-repeater-extender RS232 Repeater]</ref> In most twisted pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. With fiber optics, repeaters can be tens or even hundreds of kilometers apart.
A repeater is an electronic device that receives a network signal, cleans it of unnecessary noise and regenerates it. The signal may be reformed or retransmitted at a higher power level, to the other side of an obstruction possibly using a different transmission medium, so that the signal can cover longer distances without degradation. Commercial repeaters have extended RS-232 segments from 15 meters to over a kilometer.U.S. Converters, RS232 Repeater In most twisted pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. With fiber optics, repeaters can be tens or even hundreds of kilometers apart.
中继器和集线器中继器是一种接收网络信号，清除不必要的噪声并重新产生信号的电子设备。信号可以在较高的功率水平上重组或重新传输到障碍物的另一侧，可能使用不同的介质，这样信号可以覆盖更长的距离而不会降解。商用中继器已将 RS-232段从15米延长至1公里以上。转换器，RS232中继器在大多数双绞线以太网配置中，中继器是运行长度超过100米的电缆所必需的。使用光纤，中继器可以相距数十甚至数百公里。
Repeaters work within the physical layer of the OSI model, that is, there is no end-to-end change in the physical protocol across the repeater, or repeater pair, even if a different physical layer may be used between the ends of the repeater, or repeater pair. Repeaters require a small amount of time to regenerate the signal. This can cause a [[propagation delay]] that affects network performance and may affect proper function. As a result, many network architectures limit the number of repeaters that can be used in a row, e.g., the Ethernet [[5-4-3 rule]].
Repeaters work within the physical layer of the OSI model, that is, there is no end-to-end change in the physical protocol across the repeater, or repeater pair, even if a different physical layer may be used between the ends of the repeater, or repeater pair. Repeaters require a small amount of time to regenerate the signal. This can cause a propagation delay that affects network performance and may affect proper function. As a result, many network architectures limit the number of repeaters that can be used in a row, e.g., the Ethernet 5-4-3 rule.
中继器在 OSI 模型的物理层内工作，也就是说，即使在中继器或中继器对的两端之间可能使用不同的物理层，整个中继器或中继器对的物理协议也不会发生端到端的变化。中继器需要少量的时间来再生信号。这可能导致传播延迟影响网络性能，并可能影响正常功能。因此，许多网络架构限制了可以在一行中使用的中继器的数量，例如，以太网5-4-3规则。
A repeater with multiple ports is known as hub, an [[Ethernet hub]] in Ethernet networks, a [[USB hub]] in USB networks.
* [[USB]] networks use hubs to form tiered-star topologies.
* Ethernet hubs and repeaters in LANs have been mostly obsoleted by modern [[network switch|switches]].
A repeater with multiple ports is known as hub, an Ethernet hub in Ethernet networks, a USB hub in USB networks.
* USB networks use hubs to form tiered-star topologies.
* Ethernet hubs and repeaters in LANs have been mostly obsoleted by modern switches.
具有多个端口的中继器称为集线器，即以太网中的以太网集线器，USB 网中的 USB 集线器。
* USB 网络使用集线器形成分层星型拓扑。
* 局域网中的以太网集线器和中继器大多被现代交换机所淘汰。
===Bridges===
A [[network bridge]] connects and filters traffic between two [[network segment]]s at the [[data link layer]] (layer 2) of the [[OSI model]] to form a single network. This breaks the network's collision domain but maintains a unified broadcast domain. Network segmentation breaks down a large, congested network into an aggregation of smaller, more efficient networks.
A network bridge connects and filters traffic between two network segments at the data link layer (layer 2) of the OSI model to form a single network. This breaks the network's collision domain but maintains a unified broadcast domain. Network segmentation breaks down a large, congested network into an aggregation of smaller, more efficient networks.
在 OSI 模型的数据链路层(第二层) ，网桥连接并过滤两个网段之间的通信，从而形成一个单一的网络。这打破了网络的冲突域，但保持了一个统一的广播域。网络分割将一个大型拥挤的网络分解为一个更小、更有效的网络集合。
Bridges come in three basic types:
*Local bridges: Directly connect LANs
*Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers.
*Wireless bridges: Can be used to join LANs or connect remote devices to LANs.
Bridges come in three basic types:
*Local bridges: Directly connect LANs
*Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers.
*Wireless bridges: Can be used to join LANs or connect remote devices to LANs.
桥接器有三种基本类型:
* 本地桥接器: 直接连接局域网
* 远程桥接器: 可用于在局域网之间创建广域网(WAN)链接。远程桥接器，其中的连接链路比终端网络慢，很大程度上已经被路由器所取代。
* 无线桥接器: 可用于连接局域网或将远程设备连接到局域网。
===Switches===
A [[network switch]] is a device that forwards and filters [[OSI layer 2]] [[datagram]]s ([[Frame (networking)|frames]]) between [[Computer port (hardware)|ports]] based on the destination MAC address in each frame.<ref>{{cite web
|url=http://www.webopedia.com/TERM/s/switch.html
|title=Define switch.
|publisher=WWW.Wikipedia.com
|access-date=April 8, 2008
}}</ref>
A switch is distinct from a hub in that it only forwards the frames to the physical ports involved in the communication rather than all ports connected. It can be thought of as a multi-port bridge.<ref>{{cite web|url=http://compnetworking.about.com/cs/internetworking/g/bldef_bridge.htm|title=What bridge devices and bridging do for computer networks}}</ref> It learns to associate physical ports to MAC addresses by examining the source addresses of received frames. If an unknown destination is targeted, the switch broadcasts to all ports but the source. Switches normally have numerous ports, facilitating a star topology for devices, and cascading additional switches.
A network switch is a device that forwards and filters OSI layer 2 datagrams (frames) between ports based on the destination MAC address in each frame.
A switch is distinct from a hub in that it only forwards the frames to the physical ports involved in the communication rather than all ports connected. It can be thought of as a multi-port bridge. It learns to associate physical ports to MAC addresses by examining the source addresses of received frames. If an unknown destination is targeted, the switch broadcasts to all ports but the source. Switches normally have numerous ports, facilitating a star topology for devices, and cascading additional switches.
网络交换机是一种设备，它根据每帧中的目标 MAC 地址在端口之间转发和过滤 OSI 第2层数据报(帧)。交换机与集线器的区别在于，它只将帧转发给通信中涉及的物理端口，而不是所有连接的端口。它可以被认为是一个多端口的桥梁。它通过检查接收到的帧的源地址来学习将物理端口与 MAC 地址关联。如果目标是一个未知的目的地，交换机广播到所有端口，但源。交换机通常有许多端口，方便了设备的星型拓扑结构，并且级联了额外的交换机。
[[Network switch#Layer-specific functionality|Multi-layer switches]] are capable of routing based on layer 3 addressing or additional logical levels. The term ''switch'' is often used loosely to include devices such as routers and bridges, as well as devices that may distribute traffic based on load or based on application content (e.g., a Web [[Uniform Resource Locator|URL]] identifier).
Multi-layer switches are capable of routing based on layer 3 addressing or additional logical levels. The term switch is often used loosely to include devices such as routers and bridges, as well as devices that may distribute traffic based on load or based on application content (e.g., a Web URL identifier).
多层交换机能够基于第3层寻址或其他逻辑级别进行路由。交换机这个术语通常被广泛地用于包括路由器和桥接器等设备，以及可能根据负载或应用程序内容(例如，Web URL 标识符)分配流量的设备。
===Routers===
[[File:Adsl connections.jpg|thumb|right|A typical home or small office router showing the [[ADSL]] telephone line and [[Ethernet]] network cable connections]]
A [[Router (computing)|router]] is an [[internetworking]] device that forwards [[Packet (information technology)|packets]] between networks by processing the routing information included in the packet or datagram (Internet protocol information from layer 3). The routing information is often processed in conjunction with the [[routing table]] (or forwarding table). A router uses its routing table to determine where to forward packets. A destination in a routing table can include a "null" interface, also known as the "black hole" interface because data can go into it, however, no further processing is done for said data, i.e. the packets are dropped.
A router is an internetworking device that forwards packets between networks by processing the routing information included in the packet or datagram (Internet protocol information from layer 3). The routing information is often processed in conjunction with the routing table (or forwarding table). A router uses its routing table to determine where to forward packets. A destination in a routing table can include a "null" interface, also known as the "black hole" interface because data can go into it, however, no further processing is done for said data, i.e. the packets are dropped.
路由器是一种互联网设备，它通过处理包含在数据包或数据报中的路由信息(来自第3层的因特网协议信息)在网络之间转发数据包。路由信息通常与路由表(或转发表)一起处理。路由器使用其路由表来确定转发数据包的位置。路由表中的目的地可以包含一个“ null”接口，也称为“黑洞”接口，因为数据可以进入该接口，但是不会对所述数据进行进一步处理，即。数据包被丢弃了。
===Modems===
[[Modem]]s (MOdulator-DEModulator) are used to connect network nodes via wire not originally designed for digital network traffic, or for wireless. To do this one or more [[carrier signal]]s are [[modulation|modulated]] by the digital signal to produce an [[analog signal]] that can be tailored to give the required properties for transmission. Modems are commonly used for telephone lines, using a [[digital subscriber line]] technology.
Modems (MOdulator-DEModulator) are used to connect network nodes via wire not originally designed for digital network traffic, or for wireless. To do this one or more carrier signals are modulated by the digital signal to produce an analog signal that can be tailored to give the required properties for transmission. Modems are commonly used for telephone lines, using a digital subscriber line technology.
调制解调器(调制解调器)用于通过不是最初为数字网络流量或无线设计的有线连接网络节点。为此，一个或多个载波信号被数字信号调制以产生模拟信号，该模拟信号可以被调整以提供传输所需的特性。调制解调器通常用于电话线路，使用 DSL 技术。
===Firewalls===
A [[Firewall (computing)|firewall]] is a network device for controlling network security and access rules. Firewalls are typically configured to reject access requests from unrecognized sources while allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in [[cyberattack|cyber attack]]s.
A firewall is a network device for controlling network security and access rules. Firewalls are typically configured to reject access requests from unrecognized sources while allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in cyber attacks.
= = 防火墙 = = 防火墙是控制网络安全和访问规则的网络设备。防火墙通常配置为拒绝来自未识别源的访问请求，同时允许来自已识别源的操作。防火墙在网络安全中的重要作用与网络攻击的不断增加并行发展。
==Classification==
The study of network topology recognizes eight basic topologies: point-to-point, bus, star, ring or circular, mesh, tree, hybrid, or daisy chain.<ref name="Bicsi, B. 2002">{{cite book |author=Bicsi, B. |date=2002 |title=Network Design Basics for Cabling Professionals |publisher=McGraw-Hill Professional |isbn=9780071782968}}</ref>
The study of network topology recognizes eight basic topologies: point-to-point, bus, star, ring or circular, mesh, tree, hybrid, or daisy chain.
= = 分类 = = 网络拓扑的研究识别八种基本拓扑: 点对点、总线、星形、环形或圆形、网格、树形、混合或雏菊链。
===Point-to-point===
{{main article|Point-to-point (telecommunications)}}
The simplest topology with a dedicated link between two endpoints. Easiest to understand, of the variations of point-to-point topology, is a point-to-point [[communication channel]] that appears, to the user, to be permanently associated with the two endpoints. A child's [[tin can telephone]] is one example of a ''physical dedicated'' channel.
The simplest topology with a dedicated link between two endpoints. Easiest to understand, of the variations of point-to-point topology, is a point-to-point communication channel that appears, to the user, to be permanently associated with the two endpoints. A child's tin can telephone is one example of a physical dedicated channel.
= = = 点到点 = = = 最简单的拓扑，在两个端点之间有专用链接。对于点对点拓扑的变化，最容易理解的是一个点对点通信通道，在用户看来，它似乎与两个端点永久关联。儿童锡罐电话是一个物理专用频道的例子。
Using [[circuit-switching]] or [[packet-switching]] technologies, a point-to-point circuit can be set up dynamically and dropped when no longer needed. Switched point-to-point topologies are the basic model of conventional [[telephony]].
Using circuit-switching or packet-switching technologies, a point-to-point circuit can be set up dynamically and dropped when no longer needed. Switched point-to-point topologies are the basic model of conventional telephony.
使用电路交换或分组交换技术，点对点电路可以动态设置，并在不再需要时丢弃。点对点交换拓扑是传统电话的基本模型。
The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers and has been expressed as [[Metcalfe's Law]].
The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers and has been expressed as Metcalfe's Law.
永久性点对点网络的价值在于两个端点之间不受阻碍的通信。按需点对点连接的价值与潜在用户对的数量成正比，并被表示为梅特卡夫定律。
===Daisy chain===
[[Daisy chain (electrical engineering)|Daisy chaining]] is accomplished by connecting each computer in series to the next. If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination. A daisy-chained network can take two basic forms: linear and ring.
Daisy chaining is accomplished by connecting each computer in series to the next. If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination. A daisy-chained network can take two basic forms: linear and ring.
= = 雏菊链 = = 雏菊链是通过将每台计算机串联到下一台计算机来完成的。如果一条消息是打算发送给计算机的，那么每个系统都会按照顺序反弹它，直到它到达目的地。菊花链网络有两种基本形式: 线性网络和环状网络。
* A '''[[Linear bus topology|linear topology]]''' puts a two-way link between one computer and the next. However, this was expensive in the early days of computing, since each computer (except for the ones at each end) required two receivers and two transmitters.
* By connecting the computers at each end of the chain, a '''[[ring topology]]''' can be formed. When a [[Node (networking)|node]] sends a message, the message is processed by each computer in the ring. An advantage of the ring is that the number of transmitters and receivers can be cut in half. Since a message will eventually loop all of the way around, transmission does not need to go both directions. Alternatively, the ring can be used to improve fault tolerance. If the ring breaks at a particular link then the transmission can be sent via the reverse path thereby ensuring that all nodes are always connected in the case of a single failure.
* A linear topology puts a two-way link between one computer and the next. However, this was expensive in the early days of computing, since each computer (except for the ones at each end) required two receivers and two transmitters.
* By connecting the computers at each end of the chain, a ring topology can be formed. When a node sends a message, the message is processed by each computer in the ring. An advantage of the ring is that the number of transmitters and receivers can be cut in half. Since a message will eventually loop all of the way around, transmission does not need to go both directions. Alternatively, the ring can be used to improve fault tolerance. If the ring breaks at a particular link then the transmission can be sent via the reverse path thereby ensuring that all nodes are always connected in the case of a single failure.
* 线性拓扑在一台计算机和下一台计算机之间建立双向联系。然而，这在计算的早期是昂贵的，因为每台计算机(除了两端的计算机)需要两个接收器和两个发射器。
* 通过连接链条两端的计算机，可以形成环状拓扑结构。当节点发送消息时，环中的每台计算机都会处理该消息。这种环的一个优点是发射机和接收机的数量可以减少一半。由于信息最终会循环播放，所以传输不需要双向传播。或者，该环可用于提高容错性。如果环在一个特定的链路断开，那么传输可以通过反向路径发送，从而确保在单个故障的情况下所有节点总是连接在一起。
===Bus===
[[File:BusNetwork.svg|thumb|Bus network topology]]
{{Main article|Bus network}}
In local area networks using bus topology, each node is connected by interface connectors to a single central cable. This is the 'bus', also referred to as the [[Backbone network|backbone]], or [[Trunk (telecommunications)|trunk]] – all [[data transmission]] between nodes in the network is transmitted over this common transmission medium and is able to be [[Receiver (Information Theory)|received]] by all nodes in the network simultaneously.<ref name="Groth"/>
thumb|Bus network topology
In local area networks using bus topology, each node is connected by interface connectors to a single central cable. This is the 'bus', also referred to as the backbone, or trunk – all data transmission between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network simultaneously.
= = 总线 = = = 拇指 | 总线网络拓扑在使用总线拓扑的局域网中，每个节点通过接口连接器连接到一根中央电缆。这就是“总线”，也被称为骨干，或者干线——网络中的所有节点之间的数据传输都通过这个公共介质传输，并且能够被网络中的所有节点同时接收。
A signal containing the address of the intended receiving machine travels from a source machine in both directions to all machines connected to the bus until it finds the intended recipient, which then accepts the data. If the machine address does not match the intended address for the data, the data portion of the signal is ignored. Since the bus topology consists of only one wire it is less expensive to implement than other topologies, but the savings are offset by the higher cost of managing the network. Additionally, since the network is dependent on the single cable, it can be the [[single point of failure]] of the network. In this topology data being transferred may be accessed by any node.
A signal containing the address of the intended receiving machine travels from a source machine in both directions to all machines connected to the bus until it finds the intended recipient, which then accepts the data. If the machine address does not match the intended address for the data, the data portion of the signal is ignored. Since the bus topology consists of only one wire it is less expensive to implement than other topologies, but the savings are offset by the higher cost of managing the network. Additionally, since the network is dependent on the single cable, it can be the single point of failure of the network. In this topology data being transferred may be accessed by any node.
包含预定接收机地址的信号从源机向两个方向传播到连接到总线的所有机器，直到找到预定接收机，然后接受数据。如果机器地址与数据的预期地址不匹配，则忽略信号的数据部分。由于总线拓扑只包含一个线路，因此实现它的成本比其他拓扑要低，但是节省的成本被更高的网络管理成本所抵消。此外，由于网络依赖于单根电缆，它可以成为网络的单点故障。在此拓扑中，所传输的数据可由任何节点访问。
====Linear bus====
In a linear bus network, all of the nodes of the network are connected to a common transmission medium which has just two endpoints. When the electrical signal reaches the end of the bus, the signal is reflected back down the line, causing unwanted interference. To prevent this, the two endpoints of the bus are normally terminated with a device called a [[Electrical termination|terminator]].
In a linear bus network, all of the nodes of the network are connected to a common transmission medium which has just two endpoints. When the electrical signal reaches the end of the bus, the signal is reflected back down the line, causing unwanted interference. To prevent this, the two endpoints of the bus are normally terminated with a device called a terminator.
在线性总线网络中，网络的所有节点都连接到一个只有两个端点的公共介质上。当电信号到达总线末端时，信号沿着线路反射回去，造成不必要的干扰。为了防止这种情况，总线的两个端点通常用一个称为终止器的设备终止。
====Distributed bus====
In a distributed bus network, all of the nodes of the network are connected to a common transmission medium with more than two endpoints, created by adding branches to the main section of the transmission medium – the physical distributed bus topology functions in exactly the same fashion as the physical linear bus topology because all nodes share a common transmission medium.
In a distributed bus network, all of the nodes of the network are connected to a common transmission medium with more than two endpoints, created by adding branches to the main section of the transmission medium – the physical distributed bus topology functions in exactly the same fashion as the physical linear bus topology because all nodes share a common transmission medium.
分布式总线在一个分布式总线网络中，所有的网络节点都连接到一个具有两个以上端点的公共介质，这是通过在介质的主要部分添加分支而创建的——物理分布式总线拓扑功能与物理线性总线拓扑完全相同，因为所有节点都共享一个公共介质。
===Star===
{{Main article|Star network}}
[[File:StarNetwork.svg|thumb|Star network topology]]
In star topology, every peripheral node (computer workstation or any other peripheral) is connected to a central node called a hub or switch. The hub is the server and the peripherals are the clients. The network does not necessarily have to resemble a star to be classified as a star network, but all of the peripheral nodes on the network must be connected to one central hub. All traffic that traverses the network passes through the central hub, which acts as a [[Repeater|signal repeater]].
thumb|Star network topology
In star topology, every peripheral node (computer workstation or any other peripheral) is connected to a central node called a hub or switch. The hub is the server and the peripherals are the clients. The network does not necessarily have to resemble a star to be classified as a star network, but all of the peripheral nodes on the network must be connected to one central hub. All traffic that traverses the network passes through the central hub, which acts as a signal repeater.
星型网络拓扑在星型拓扑中，每个外围节点(计算机工作站或任何其他外围节点)都连接到一个称为集线器或交换机的中心节点。集线器是服务器，外围设备是客户机。网络不一定要像一颗星才能被归类为星型网络，但是网络上的所有外围节点必须连接到一个中心枢纽。所有穿过网络的流量都要经过中心枢纽，中心枢纽起到信号中继器的作用。
The star topology is considered the easiest topology to design and implement. One advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure. Also, since all peripheral communication must flow through the central hub, the aggregate central bandwidth forms a network bottleneck for large clusters.
The star topology is considered the easiest topology to design and implement. One advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure. Also, since all peripheral communication must flow through the central hub, the aggregate central bandwidth forms a network bottleneck for large clusters.
星型拓扑被认为是最容易设计和实现的拓扑。星型拓扑的一个优点是添加额外节点的简单性。星型拓扑的主要缺点是中心代表单点故障。而且，由于所有外围通信都必须通过中央集线器，因此聚合的中央带宽对于大型集群来说形成了网络瓶颈。
====Extended star====
The extended star network topology extends a physical star topology by one or more repeaters between the central node and the [[peripheral]] (or 'spoke') nodes. The repeaters are used to extend the maximum transmission distance of the physical layer, the point-to-point distance between the central node and the peripheral nodes. Repeaters allow greater transmission distance, further than would be possible using just the transmitting power of the central node. The use of repeaters can also overcome limitations from the standard upon which the physical layer is based.
The extended star network topology extends a physical star topology by one or more repeaters between the central node and the peripheral (or 'spoke') nodes. The repeaters are used to extend the maximum transmission distance of the physical layer, the point-to-point distance between the central node and the peripheral nodes. Repeaters allow greater transmission distance, further than would be possible using just the transmitting power of the central node. The use of repeaters can also overcome limitations from the standard upon which the physical layer is based.
扩展星型扩展星型网络拓扑在中央节点和外围(或“辐射”)节点之间通过一个或多个中继器扩展物理星型拓扑。中继器用于延长物理层的最大传输距离、中心节点与外围节点之间的点对点距离。中继器允许更大的传输距离，比仅仅使用中心节点的传输功率可能达到的距离更远。中继器的使用还可以克服物理层所基于的标准的局限性。
A physical extended star topology in which repeaters are replaced with hubs or switches is a type of hybrid network topology and is referred to as a physical hierarchical star topology, although some texts make no distinction between the two topologies.
A physical extended star topology in which repeaters are replaced with hubs or switches is a type of hybrid network topology and is referred to as a physical hierarchical star topology, although some texts make no distinction between the two topologies.
物理扩展星形拓扑，其中中继器被集线器或交换机取代，是一种混合网络拓扑，被称为物理层次星形拓扑，尽管一些文本没有区分这两种拓扑。
A physical hierarchical star topology can also be referred as a tier-star topology, this topology differs from a [[tree topology]] in the way star networks are connected together. A tier-star topology uses a central node, while a tree topology uses a central bus and can also be referred as a star-bus network.
A physical hierarchical star topology can also be referred as a tier-star topology, this topology differs from a tree topology in the way star networks are connected together. A tier-star topology uses a central node, while a tree topology uses a central bus and can also be referred as a star-bus network.
物理层次星型拓扑也可以称为层次星型拓扑，这种拓扑在星型网络连接方式上不同于树型拓扑。层星型拓扑使用中心节点，而树型拓扑使用中心总线，也可以称为星型总线网络。
====Distributed star====
A distributed star is a network topology that is composed of individual networks that are based upon the physical star topology connected in a linear fashion – i.e., 'daisy-chained' – with no central or top level connection point (e.g., two or more 'stacked' hubs, along with their associated star connected nodes or 'spokes').
A distributed star is a network topology that is composed of individual networks that are based upon the physical star topology connected in a linear fashion – i.e., 'daisy-chained' – with no central or top level connection point (e.g., two or more 'stacked' hubs, along with their associated star connected nodes or 'spokes').
分布式星型是一种由单个网络组成的网络拓扑，这些网络基于物理星型拓扑结构，以线性方式连接——例如，“菊花链”——没有中央或顶层连接点(例如，两个或多个“堆叠”集线器，以及它们相关的星型连接节点或“辐条”)。
===Ring===
{{Main article|Ring network}}
[[File:RingNetwork.svg|thumb|Ring network topology]]
thumb|Ring network topology
= = 戒指 = = = 拇指 | 戒指网络拓扑
A ring topology is a [[Daisy chain (electrical engineering)|daisy chain]] in a closed loop. Data travels around the ring in one direction. When one node sends data to another, the data passes through each intermediate node on the ring until it reaches its destination. The intermediate nodes repeat (retransmit) the data to keep the signal strong.<ref name="Inc, S. 2002"/> Every node is a peer; there is no hierarchical relationship of clients and servers. If one node is unable to retransmit data, it severs communication between the nodes before and after it in the bus.
A ring topology is a daisy chain in a closed loop. Data travels around the ring in one direction. When one node sends data to another, the data passes through each intermediate node on the ring until it reaches its destination. The intermediate nodes repeat (retransmit) the data to keep the signal strong. Every node is a peer; there is no hierarchical relationship of clients and servers. If one node is unable to retransmit data, it severs communication between the nodes before and after it in the bus.
环拓扑是闭环中的菊花链。数据沿着环的一个方向传播。当一个节点向另一个节点发送数据时，数据通过环上的每个中间节点，直到到达目的地。中间节点重复(重新传输)数据以保持信号强大。每个节点都是一个对等节点; 客户端和服务器之间没有层次关系。如果一个节点无法重新传输数据，它将在总线中切断节点之前和之后的通信。
Advantages:
* When the load on the network increases, its performance is better than bus topology.
* There is no need of network server to control the connectivity between workstations.
Advantages:
* When the load on the network increases, its performance is better than bus topology.
* There is no need of network server to control the connectivity between workstations.
优点:
* 当网络负载增加时，其性能优于总线拓扑。
* 不需要网络服务器来控制工作站之间的连接。
Disadvantages:
* Aggregate network bandwidth is bottlenecked by the weakest link between two nodes.
Disadvantages:
* Aggregate network bandwidth is bottlenecked by the weakest link between two nodes.
缺点:
* 聚合网络带宽受到两个节点之间最弱链接的瓶颈。
===Mesh===
{{Main article|Mesh networking}}
The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints, is approximated by [[Reed's Law]].
The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints, is approximated by Reed's Law.
假设任意两个端点(包括所有端点)的通信组都近似于里德定律，那么完全网状网络的价值与用户数的指数成正比。
====Fully connected network====
[[File:NetworkTopology-FullyConnected.png|thumb|Fully connected mesh topology]]
thumb|Fully connected mesh topology
= = = 完全连接的网络 = = = = 拇指 | 完全连接的网格拓扑
In a ''fully connected network'', all nodes are interconnected. (In [[graph theory]] this is called a [[complete graph]].) The simplest fully connected network is a two-node network. A fully connected network doesn't need to use [[packet switching]] or [[Broadcasting (networks)|broadcasting]]. However, since the number of connections grows quadratically with the number of nodes:
In a fully connected network, all nodes are interconnected. (In graph theory this is called a complete graph.) The simplest fully connected network is a two-node network. A fully connected network doesn't need to use packet switching or broadcasting. However, since the number of connections grows quadratically with the number of nodes:
在一个完全连接的网络中，所有的节点都是相互连接的。(在图论中，这叫做完全图。)最简单的完全连接网络是两节点网络。一个完全连接的网络不需要使用分组交换或广播。然而，由于连接的数量与节点的数量成二次增长:
<math>c= \frac{n(n-1)}{2}.\,</math>
c= \frac{n(n-1)}{2}.\,
C = frac { n (n-1)}{2},
This makes it impractical for large networks. This kind of topology does not trip and affect other nodes in the network.
This makes it impractical for large networks. This kind of topology does not trip and affect other nodes in the network.
这使得它不适用于大型网络。这种拓扑结构不会跳闸，也不会影响网络中的其他节点。
====Partially connected network====
[[File:NetworkTopology-Mesh.svg|thumb|Partially connected mesh topology]]
In a partially connected network, certain nodes are connected to exactly one other node; but some nodes are connected to two or more other nodes with a point-to-point link. This makes it possible to make use of some of the redundancy of mesh topology that is physically fully connected, without the expense and complexity required for a connection between every node in the network.
thumb|Partially connected mesh topology
In a partially connected network, certain nodes are connected to exactly one other node; but some nodes are connected to two or more other nodes with a point-to-point link. This makes it possible to make use of some of the redundancy of mesh topology that is physically fully connected, without the expense and complexity required for a connection between every node in the network.
部分连接网络在部分连接的网络中，某些节点恰好连接到另一个节点; 但是有些节点通过点对点链接连接到两个或更多的其他节点。这使得利用物理上完全连接的网格拓扑的一些冗余成为可能，而不需要在网络中的每个节点之间建立连接所需的开销和复杂性。
===Hybrid===
Hybrid topology is also known as hybrid network.<ref>{{Cite web|title=What is Hybrid Topology ? Advantages and Disadvantages|url=http://www.orosk.com/hybrid-topology/|url-status=dead|archive-url=https://web.archive.org/web/20160909170820/http://www.orosk.com/hybrid-topology/|archive-date=September 9, 2016|access-date=2018-01-26|website=OROSK.COM|language=en-US}}</ref> Hybrid networks combine two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a [[tree network]] (or ''star-bus network'') is a hybrid topology in which [[star network]]s are interconnected via [[bus network]]s.<ref name="Sosinsky">{{cite book |title=Networking Bible |last=Sosinsky |first=Barrie A. |page=16 |date=2009 |location=Indianapolis |publisher=Wiley Publishing |isbn=978-0-470-43131-3 |oclc=359673774 |chapter=Network Basics |chapter-url=https://books.google.com/books?id=3DOREqRZejcC&pg=PA16 |access-date=2016-03-26}}</ref><ref>{{cite book |url=https://books.google.com/books?id=gnuwPpBcO-MC&pg=RA1-PT12 |title=Understanding Computer Science (for Advanced Level): The Study Guide |last=Bradley |first=Ray |location=Cheltenham |publisher=[[Nelson Thornes]] |page=244 |isbn=978-0-7487-6147-0 |oclc=47869750 |access-date=2016-03-26|year=2001 }}</ref> However, a tree network connected to another tree network is still topologically a tree network, not a distinct network type. A hybrid topology is always produced when two different basic network topologies are connected.
Hybrid topology is also known as hybrid network. Hybrid networks combine two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network (or star-bus network) is a hybrid topology in which star networks are interconnected via bus networks. However, a tree network connected to another tree network is still topologically a tree network, not a distinct network type. A hybrid topology is always produced when two different basic network topologies are connected.
混合拓扑也称为混合网络。混合网络将两种或多种拓扑结合在一起，使得得到的网络不会显示出其中一种标准拓扑(例如，总线、星形、环形等)。例如，树形网络(或星形总线网络)是一种混合拓扑结构，其中星形网络通过总线网络相互连接。然而，一个树状网络连接到另一个树状网络，在拓扑上仍然是一个树状网络，而不是一个独特的网络类型。当两个不同的基本网络拓扑相互连接时，总会产生混合拓扑。
A ''star-ring'' network consists of two or more ring networks connected using a [[Media Access Unit|multistation access unit]] (MAU) as a centralized hub.
A star-ring network consists of two or more ring networks connected using a multistation access unit (MAU) as a centralized hub.
星环网络由两个或多个环网组成，环网使用多站接入单元(MAU)作为集中的集线器连接。
Snowflake topology is a star network of star networks.{{citation needed|date=March 2016}}
Snowflake topology is a star network of star networks.
雪花拓扑是由星形网络组成的星形网络。
Two other hybrid network types are ''hybrid mesh'' and ''hierarchical star''.<ref name="Sosinsky"/>
Two other hybrid network types are hybrid mesh and hierarchical star.
另外两种混合网络类型是混合网格和层次星型。
==Centralization==
The '''[[Star network|star topology]]''' reduces the probability of a network failure by connecting all of the peripheral nodes (computers, etc.) to a central node. When the physical star topology is applied to a logical bus network such as [[Ethernet]], this central node (traditionally a hub) rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All [[peripheral]] nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The [[failure]] of a [[transmission line]] linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the remaining peripheral nodes will be unaffected. However, the disadvantage is that the failure of the central node will cause the failure of all of the peripheral nodes.
The star topology reduces the probability of a network failure by connecting all of the peripheral nodes (computers, etc.) to a central node. When the physical star topology is applied to a logical bus network such as Ethernet, this central node (traditionally a hub) rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the remaining peripheral nodes will be unaffected. However, the disadvantage is that the failure of the central node will cause the failure of all of the peripheral nodes.
星型拓扑通过连接所有的外围节点(计算机等)来降低网络故障的可能性一个中心节点。当将物理星型拓扑应用于逻辑总线网络(例如以太网)时，这个中心节点(传统上是集线器)将从任何外围节点接收到的所有传输重新广播到网络上的所有外围节点，有时包括原始节点。因此，所有外围节点可以通过仅向中心节点发送和从中心节点接收而与所有其他节点通信。如果连接任何外围节点到中央节点的传输线发生故障，将导致该外围节点与所有其他节点隔离，但其余的外围节点将不受影响。然而，缺点是中心节点的故障将导致所有外围节点的故障。
If the central node is ''passive'', the originating node must be able to tolerate the reception of an [[Echo (phenomenon)|echo]] of its own transmission, delayed by the two-way [[round-trip time|round trip]] [[transmission time]] (i.e. to and from the central node) plus any delay generated in the central node. An ''active'' star network has an active central node that usually has the means to prevent echo-related problems.
If the central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way round trip transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems.
如果中心节点是被动的，则发起节点必须能够容忍其自身传输的回波的接收，这种回波被双向往返传输时间(即。中心节点)加上中心节点中产生的任何延迟。主动星形网络有一个主动中心节点，该节点通常具有防止回波相关问题的手段。
A '''[[tree topology]]''' (a.k.a. '''hierarchical topology''') can be viewed as a collection of star networks arranged in a [[hierarchy]]. This [[tree structure]] has individual peripheral nodes (e.g. leaves) which are required to transmit to and receive from one other node only and are not required to act as repeaters or regenerators. Unlike the star network, the functionality of the central node may be distributed.
A tree topology (a.k.a. hierarchical topology) can be viewed as a collection of star networks arranged in a hierarchy. This tree structure has individual peripheral nodes (e.g. leaves) which are required to transmit to and receive from one other node only and are not required to act as repeaters or regenerators. Unlike the star network, the functionality of the central node may be distributed.
树拓扑(又名。层次拓扑结构)可以看作是一个星形网络的集合，按层次结构排列。这个树结构有单独的外围节点(例如。只需要向另一个节点发送和从另一个节点接收，而不需要作为中继器或再生器。与星形网络不同，中心节点的功能可以分布式实现。
As in the conventional star network, individual nodes may thus still be isolated from the network by a single-point failure of a transmission path to the node. If a link connecting a leaf fails, that leaf is isolated; if a connection to a non-leaf node fails, an entire section of the network becomes isolated from the rest.
As in the conventional star network, individual nodes may thus still be isolated from the network by a single-point failure of a transmission path to the node. If a link connecting a leaf fails, that leaf is isolated; if a connection to a non-leaf node fails, an entire section of the network becomes isolated from the rest.
与传统的星型网络一样，单个节点仍然可以通过传输路径的单点故障从网络中隔离出来。如果连接叶子的链接失败，那么叶子将被隔离; 如果连接到非叶子节点失败，则网络的整个部分将与其余部分隔离。
To alleviate the amount of network traffic that comes from broadcasting all signals to all nodes, more advanced central nodes were developed that are able to keep track of the identities of the nodes that are connected to the network. These [[network switch]]es will "learn" the layout of the network by "listening" on each port during normal data transmission, examining the [[data packets]] and recording the address/identifier of each connected node and which port it is connected to in a [[lookup table]] held in memory. This lookup table then allows future transmissions to be forwarded to the intended destination only.
To alleviate the amount of network traffic that comes from broadcasting all signals to all nodes, more advanced central nodes were developed that are able to keep track of the identities of the nodes that are connected to the network. These network switches will "learn" the layout of the network by "listening" on each port during normal data transmission, examining the data packets and recording the address/identifier of each connected node and which port it is connected to in a lookup table held in memory. This lookup table then allows future transmissions to be forwarded to the intended destination only.
为了减少向所有节点广播所有信号产生的网络流量，开发了更先进的中央节点，能够跟踪连接到网络的节点的身份。这些网络交换机会在正常数据传输时“监听”每个端口，检查数据包，并记录每个连接节点的地址/标识符，以及该节点连接到内存中的查找表中的哪个端口，从而“学习”网络的布局。这个查找表只允许将来的传输转发到预期的目的地。
==Decentralization==
In a partially connected mesh topology, there are at least two nodes with two or more paths between them to provide redundant paths in case the link providing one of the paths fails. Decentralization is often used to compensate for the single-point-failure disadvantage that is present when using a single device as a central node (e.g., in star and tree networks). A special kind of mesh, limiting the number of hops between two nodes, is a [[hypercube]]. The number of arbitrary forks in mesh networks makes them more difficult to design and implement, but their decentralized nature makes them very useful.
In a partially connected mesh topology, there are at least two nodes with two or more paths between them to provide redundant paths in case the link providing one of the paths fails. Decentralization is often used to compensate for the single-point-failure disadvantage that is present when using a single device as a central node (e.g., in star and tree networks). A special kind of mesh, limiting the number of hops between two nodes, is a hypercube. The number of arbitrary forks in mesh networks makes them more difficult to design and implement, but their decentralized nature makes them very useful.
= = 地方分权 = = 在一个部分连接的网格拓扑结构中，至少有两个节点之间有两条或多条路径，以便在提供其中一条路径的链路出现故障时提供冗余路径。地方分权通常用来弥补单一设备作为中心节点时出现的单点故障缺陷(例如，在星型和树型网络中)。一种特殊的网格类型是超立方体，它限制两个节点之间的跳数。网状网络中任意分叉的数量使得它们的设计和实现更加困难，但是它们的分散性使得它们非常有用。
This is similar in some ways to a [[grid network]], where a linear or ring topology is used to connect systems in multiple directions. A multidimensional ring has a [[torus|toroidal]] topology, for instance.
This is similar in some ways to a grid network, where a linear or ring topology is used to connect systems in multiple directions. A multidimensional ring has a toroidal topology, for instance.
这在某些方面类似于网格网络，其中使用线性或环形拓扑将多个方向的系统连接起来。例如，多维环具有环形拓扑结构。
A ''fully connected network'', ''complete topology'', or ''full mesh topology'' is a network topology in which there is a direct link between all pairs of nodes. In a fully connected network with n nodes, there are <math>\frac{n(n-1)}{2}\,</math> direct links. Networks designed with this topology are usually very expensive to set up, but provide a high degree of reliability due to the multiple paths for data that are provided by the large number of redundant links between nodes. This topology is mostly seen in [[military]] applications.
A fully connected network, complete topology, or full mesh topology is a network topology in which there is a direct link between all pairs of nodes. In a fully connected network with n nodes, there are \frac{n(n-1)}{2}\, direct links. Networks designed with this topology are usually very expensive to set up, but provide a high degree of reliability due to the multiple paths for data that are provided by the large number of redundant links between nodes. This topology is mostly seen in military applications.
完全连接的网络、完全拓扑或完全网状拓扑是一种网络拓扑，其中所有节点对之间都有直接链接。在具有 n 个节点的完全连通网络中，存在 frc { n (n-1)}{2}直接链路。使用这种拓扑结构设计的网络通常建立起来非常昂贵，但是由于节点之间大量冗余链路为数据提供了多条路径，因此提供了高度的可靠性。这种拓扑结构主要用于军事应用程序。
==See also==
{{div col|colwidth=20em}}
* [[Broadcast communication network]]
* [[Butterfly network]]
* [[Computer network diagram]]
* [[Gradient network]]
* [[Internet topology]]
* [[Network simulation]]
* [[Relay network]]
* [[Rhizome (philosophy)]]
* [[Scale-free network]]
* [[Shared mesh]]
* [[Switched communication network]]
* [[Switched mesh]]
{{div col end}}
* Broadcast communication network
* Butterfly network
* Computer network diagram
* Gradient network
* Internet topology
* Network simulation
* Relay network
* Rhizome (philosophy)
* Scale-free network
* Shared mesh
* Switched communication network
* Switched mesh
* 广播通信网络
* 蝴蝶网络
* 网路图
* 互联网拓扑
* 网络仿真
* 中继网络
* 根无尺度网络
* 共享网络
* 交换通信网络
* 交换网络
==References==
{{Reflist}}
==External links==
{{Commons|Topology (Network)}}
* [https://web.archive.org/web/20141106222358/http://www.nyu.edu/its/pubs/architecture/kyriannis-tetrahedroncore.pdf Tetrahedron Core Network:] Application of a tetrahedral structure to create a resilient partial-mesh 3-dimensional campus backbone data network
* Tetrahedron Core Network: Application of a tetrahedral structure to create a resilient partial-mesh 3-dimensional campus backbone data network
= = 外部链接 = =
* 四面体核心网: 应用四面体结构创建弹性局部网格三维校园主干数据网
{{Network topologies}}
{{DEFAULTSORT:Network topology}}
[[Category:Network topology| ]]
[[Category:Decentralization]]
Category:Decentralization
分类: 地方分权
<noinclude>
<small>This page was moved from [[wikipedia:en:Network topology]]. Its edit history can be viewed at [[网络拓扑/edithistory]]</small></noinclude>
[[Category:待整理页面]]
{{short description|Arrangement of the elements of a communication network}}
{{about|the topology of communication networks|the topology of electrical networks|Topology (electrical circuits)|the topology of transport networks|Transport topology}}
{{Network Science}}
'''Network topology''' is the arrangement of the elements ([[Data link|links]], [[Node (networking)|nodes]], etc.) of a communication network.<ref name="Groth">{{Cite book
|last =Groth
|first = David
|author2=Toby Skandier
|title = Network+ Study Guide, Fourth Edition
|publisher = Sybex, Inc.
|year = 2005
|isbn = 0-7821-4406-3
}}</ref><ref name="atis">{{Cite web|author=ATIS committee PRQC|title=mesh topology|url=http://www.atis.org/glossary/definition.aspx?id=3516|url-status=dead|archive-url=http://archive.today/2013.04.14-061003/http://www.atis.org/glossary/definition.aspx?id=3516|archive-date=April 14, 2013|access-date=2008-10-10|work=ATIS Telecom Glossary 2007|publisher=[[Alliance for Telecommunications Industry Solutions]]}}</ref> Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including [[command and control]] radio networks,<ref name="GrantC2"/> industrial [[Fieldbus|fieldbusses]] and [[computer networks]].
Network topology is the arrangement of the elements (links, nodes, etc.) of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.
网络拓扑是元素(链接、节点等)的排列通讯网络。网络拓扑可用以界定或描述各类电讯网络的布局，包括指挥及控制无线电网络、工业现场总线及电脑网络。
Network topology is the [[topological]]<ref name="Chiang04">{{cite journal|last1=Chiang|first1=Mung|last2=Yang|first2=Michael|year=2004|title=Towards Network X-ities From a Topological Point of View: Evolvability and Scalability|url=http://www.cs.unm.edu/~karlinjf/papers/allerton.pdf|url-status=dead|journal=Proc. 42nd Allerton Conference|archive-url=https://web.archive.org/web/20130921053241/http://www.cs.unm.edu/~karlinjf/papers/allerton.pdf|archive-date=September 21, 2013}}</ref> structure of a network and may be depicted physically or logically. It is an application of [[graph theory]]<ref name="GrantC2">{{cite book|title=Network Topology in Command and Control |editor= Grant, T. J. |series= Advances in Information Security, Privacy, and Ethics |publisher= IGI Global |year= 2014 |url= https://books.google.com/books?id=zBOXBQAAQBAJ |pages= xvii, 228, 250 |isbn= 9781466660595 }}</ref> wherein communicating devices are modeled as nodes and the connections between the devices are modeled as links or lines between the nodes. '''Physical topology''' is the placement of the various components of a network (e.g., device location and cable installation), while '''logical topology''' illustrates how data flows within a network. Distances between nodes, physical interconnections, [[Bit rate|transmission rates]], or signal types may differ between two different networks, yet their logical topologies may be identical. A network’s physical topology is a particular concern of the [[physical layer]] of the [[OSI model]].
Network topology is the topological structure of a network and may be depicted physically or logically. It is an application of graph theory wherein communicating devices are modeled as nodes and the connections between the devices are modeled as links or lines between the nodes. Physical topology is the placement of the various components of a network (e.g., device location and cable installation), while logical topology illustrates how data flows within a network. Distances between nodes, physical interconnections, transmission rates, or signal types may differ between two different networks, yet their logical topologies may be identical. A network’s physical topology is a particular concern of the physical layer of the OSI model.
网络拓扑是网络的拓扑结构，可以在物理上或逻辑上描述。它是图论的一个应用，其中通信设备被建模为节点，设备之间的连接被建模为节点之间的链接或线。物理拓扑是放置网络的各种组件(例如，设备位置和电缆安装) ，而逻辑拓扑说明了数据如何在网络中流动。节点之间的距离、物理互连、传输速率或信号类型在两个不同的网络之间可能不同，但它们的逻辑拓扑可能是相同的。网络的物理拓扑结构是 OSI 模型物理层特别关注的问题。
Examples of network topologies are found in [[local area network]]s ([[LAN]]), a common computer network installation. Any given node in the LAN has one or more physical links to other devices in the network; graphically mapping these links results in a geometric shape that can be used to describe the physical topology of the network. A wide variety of physical topologies have been used in LANs, including [[ring network|ring]], [[bus network|bus]], [[mesh network|mesh]] and [[star network|star]]. Conversely, mapping the [[Traffic flow (computer networking)|data flow]] between the components determines the logical topology of the network. In comparison, [[CAN bus|Controller Area Networks]], common in vehicles, are primarily distributed [[control system]] networks of one or more controllers interconnected with sensors and actuators over, invariably, a physical bus topology.
Examples of network topologies are found in local area networks (LAN), a common computer network installation. Any given node in the LAN has one or more physical links to other devices in the network; graphically mapping these links results in a geometric shape that can be used to describe the physical topology of the network. A wide variety of physical topologies have been used in LANs, including ring, bus, mesh and star. Conversely, mapping the data flow between the components determines the logical topology of the network. In comparison, Controller Area Networks, common in vehicles, are primarily distributed control system networks of one or more controllers interconnected with sensors and actuators over, invariably, a physical bus topology.
网络拓扑的示例可以在局域网(LAN)中找到，LAN 是一种常见的计算机网络安装。局域网中的任何给定节点都有一个或多个到网络中其他设备的物理链路; 通过图形化地映射这些链路，得到一个可用于描述网络物理拓扑结构的几何形状。各种各样的物理拓扑在局域网中得到了广泛的应用，包括环形、总线、网格和星形。相反，在组件之间映射数据流决定了网络的逻辑拓扑。相比之下，车辆中常见的控制器区域网络主要是由一个或多个控制器组成的管理系统网络，这些控制器通过物理总线拓扑结构与传感器和执行器相互连接。
==Topologies==
[[File:NetworkTopologies.svg|right|thumb|300px|Diagram of different network topologies.]]
right|thumb|300px|Diagram of different network topologies.
= = 拓扑 = = 右图 | 300px | 不同网络拓扑图。
Two basic categories of network topologies exist, physical topologies and logical topologies.<ref name="Inc, S. 2002">Inc, S., (2002) . Networking Complete. Third Edition. San Francisco: Sybex</ref>
Two basic categories of network topologies exist, physical topologies and logical topologies.Inc, S., (2002) . Networking Complete. Third Edition. San Francisco: Sybex
存在两种基本的网络拓扑，即物理拓扑和逻辑拓扑。网络完成。第三版。旧金山: Sybex
The [[transmission medium]] layout used to link devices is the physical topology of the network. For conductive or fiber optical mediums, this refers to the layout of [[Structured cabling|cabling]], the locations of nodes, and the links between the nodes and the cabling.<ref name="Groth"/> The physical topology of a network is determined by the capabilities of the network access devices and media, the level of control or fault tolerance desired, and the cost associated with cabling or telecommunication circuits.
The transmission medium layout used to link devices is the physical topology of the network. For conductive or fiber optical mediums, this refers to the layout of cabling, the locations of nodes, and the links between the nodes and the cabling. The physical topology of a network is determined by the capabilities of the network access devices and media, the level of control or fault tolerance desired, and the cost associated with cabling or telecommunication circuits.
用于连接设备的介质布局是网络的物理拓扑结构。对于导电或光纤介质，这是指布线的布局，节点的位置，以及节点和布线之间的链接。网络的物理拓扑结构取决于网络接入设备和介质的能力、所需的控制或容错水平以及与布线或电信电路相关的成本。
In contrast, logical topology is the way that the signals act on the network media,<ref>{{citation |url=http://www.webopedia.com/quick_ref/topologies.asp |title=What Are Network Topologies? |access-date=2016-09-17}}</ref> or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices.<ref>{{Cite journal |author1=Leonardi, E. |author2=Mellia, M. |author3= Marsan, M. A. |date=2000 |title=Algorithms for the Logical Topology Design in WDM All-Optical Networks |url=https://www.researchgate.net/publication/2414623 |journal=Optical Networks Magazine |pages=35–46}}</ref> A network's logical topology is not necessarily the same as its physical topology. For example, the original [[twisted pair Ethernet]] using [[repeater hub]]s was a logical bus topology carried on a physical star topology. [[Token Ring]] is a logical ring topology, but is wired as a physical star from the [[media access unit]]. Physically, [[Avionics Full-Duplex Switched Ethernet|AFDX]] can be a cascaded star topology of multiple dual redundant Ethernet switches; however, the AFDX [[Avionics Full-Duplex Switched Ethernet#Virtual links|Virtual links]] are modeled as [[Time-division multiplexing|time-switched]] single-transmitter bus connections, thus following the safety model of a [[ARINC 429|single-transmitter bus topology]] previously used in aircraft. Logical topologies are often closely associated with [[media access control]] methods and protocols. Some networks are able to dynamically change their logical topology through configuration changes to their [[Router (computing)|router]]s and switches.
In contrast, logical topology is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices. A network's logical topology is not necessarily the same as its physical topology. For example, the original twisted pair Ethernet using repeater hubs was a logical bus topology carried on a physical star topology. Token Ring is a logical ring topology, but is wired as a physical star from the media access unit. Physically, AFDX can be a cascaded star topology of multiple dual redundant Ethernet switches; however, the AFDX Virtual links are modeled as time-switched single-transmitter bus connections, thus following the safety model of a single-transmitter bus topology previously used in aircraft. Logical topologies are often closely associated with media access control methods and protocols. Some networks are able to dynamically change their logical topology through configuration changes to their routers and switches.
相比之下，逻辑拓扑是信号作用于网络媒体的方式，或者是数据从一个设备通过网络传递到下一个设备的方式，而不考虑设备之间的物理互连。网络的逻辑拓扑不一定与其物理拓扑相同。例如，使用中继器集线器的原始双绞线以太网是在物理星型拓扑上进行的逻辑总线拓扑。令牌环是一个逻辑环拓扑，但是从媒体访问单元以物理星形连接。在物理上，AFDX 可以是多个双冗余以太网交换机的级联星型拓扑; 然而，AFDX 虚拟链路被建模为时间交换的单发射机总线连接，因此遵循了以前在飞机上使用的单发射机总线拓扑的安全模型。逻辑拓扑通常与媒体访问控制方法和协议密切相关。有些网络能够通过改变其路由器和交换机的配置来动态改变其逻辑拓扑结构。
==Links==
{{further|data transmission}}
The transmission media (often referred to in the literature as the ''physical media'') used to link devices to form a computer network include [[electrical cables]] ([[Ethernet]], [[HomePNA]], [[power line communication]], [[G.hn]]), [[optical fiber]] ([[fiber-optic communication]]), and [[radio waves]] ([[wireless networking]]). In the [[OSI model]], these are defined at layers 1 and 2 — the physical layer and the data link layer.
The transmission media (often referred to in the literature as the physical media) used to link devices to form a computer network include electrical cables (Ethernet, HomePNA, power line communication, G.hn), optical fiber (fiber-optic communication), and radio waves (wireless networking). In the OSI model, these are defined at layers 1 and 2 — the physical layer and the data link layer.
用于连接设备形成计算机网络的传输媒介(通常在文献中称为物理媒介)包括电缆(以太网、 HomepNA、电力线通信、 G.hn)、光纤(光纤通讯)和无线电波(无线网络)。在 OSI 模型中，这些定义在第1层和第2层ーー物理层和数据链路层。
A widely adopted ''family'' of transmission media used in local area network ([[LAN]]) technology is collectively known as [[Ethernet]]. The media and protocol standards that enable communication between networked devices over Ethernet are defined by [[IEEE 802.3]]. Ethernet transmits data over both copper and fiber cables. Wireless LAN standards (e.g. those defined by [[IEEE 802.11]]) use [[radio waves]], or others use [[IrDA|infrared]] signals as a transmission medium. [[Power line communication]] uses a building's power cabling to transmit data.
A widely adopted family of transmission media used in local area network (LAN) technology is collectively known as Ethernet. The media and protocol standards that enable communication between networked devices over Ethernet are defined by IEEE 802.3. Ethernet transmits data over both copper and fiber cables. Wireless LAN standards (e.g. those defined by IEEE 802.11) use radio waves, or others use infrared signals as a transmission medium. Power line communication uses a building's power cabling to transmit data.
局域网(LAN)技术中广泛采用的传输媒体系统统称为以太网。IEEE 802.3定义了支持网络设备通过以太网进行通信的媒体和协议标准。以太网通过铜缆和光缆传输数据。无线局域网标准(例如:。IEEE 802.11)定义的介质使用无线电波，或者使用红外线信号。电力线通信使用建筑物的电力电缆传输数据。
===Wired technologies===
[[File:Fibreoptic.jpg|thumb|upright=0.7|alt=Bundle of glass threads with light emitting from the ends|[[Fiber optic cables]] are used to transmit light from one computer/network node to another]]
The orders of the following wired technologies are, roughly, from slowest to fastest transmission speed.
The orders of the following wired technologies are, roughly, from slowest to fastest transmission speed.
以下有线技术的顺序大致是从最慢到最快的传输速度。
*''[[Coaxial cable]]'' is widely used for cable television systems, office buildings, and other work-sites for local area networks. The cables consist of copper or aluminum wire surrounded by an insulating layer (typically a flexible material with a high dielectric constant), which itself is surrounded by a conductive layer. The insulation between the conductors helps maintain the characteristic impedance of the cable which can help improve its performance. Transmission speed ranges from 200 million bits per second to more than 500 million bits per second.
*''[[ITU-T]] [[G.hn]]'' technology uses existing [[home wiring]] ([[Ethernet over coax|coaxial cable]], phone lines and [[Power line communication|power lines]]) to create a high-speed (up to 1 Gigabit/s) local area network.
* ''[[Signal trace]]s'' on [[printed circuit board]]s are common for board-level serial communication, particularly between certain types integrated circuits, a common example being [[Serial Peripheral Interface Bus|SPI]].
*''[[Ribbon cable]]'' (untwisted and possibly unshielded) has been a cost-effective media for serial protocols, especially within metallic enclosures or rolled within copper braid or foil, over short distances, or at lower data rates. Several serial network protocols can be deployed without shielded or twisted pair cabling, that is, with "flat" or "ribbon" cable, or a hybrid flat/twisted ribbon cable, should [[Electromagnetic compatibility|EMC]], length, and [[Bandwidth (computing)|bandwidth]] constraints permit: [[RS-232]],<ref>[https://www.jameco.com/z/GCAR11-R-Cable-Serial-Male-To-Female-25L-4-DB25-M-DB25-28-AWG-300V-Gray_12408.html Cable Serial Male To Female 25L 4' DB25 M-DB25 28 AWG 300V Gray], Part no.: 12408, Jameco Electronics.</ref> [[RS-422]], [[RS-485]],<ref>AN-1057 [http://www.ti.com/lit/an/snla049b/snla049b.pdf Ten ways to bulletproof RS-485 Interfaces], [[Texas Instruments]], p. 5. </ref> [[CAN Bus|CAN]],<ref>[[CANopen]],[https://www.phoenixcontact.com/assets/downloads_ed/global/web_dwl_technical_info/CANopen.pdf CANopen DR-303 V1.0 Cabling and Connector Pin Assignment], [[CAN in Automation]], p. 10.</ref> [[IEEE-488|GPIB]], [[SCSI]],<ref>Advantech Co., Ltd., Cable 50-Pin SCSI Ribbon type # PCL-10152-3E ([[Mouser Electronics]] #923-PCL-10152-3E)</ref> etc.
*''[[Twisted pair]] wire'' is the most widely used medium for all telecommunication.{{cn|date=May 2021}} Twisted-pair cabling consist of copper wires that are twisted into pairs. Ordinary telephone wires consist of two insulated copper wires twisted into pairs. Computer network cabling (wired [[Ethernet]] as defined by [[IEEE 802.3]]) consists of 4 pairs of copper cabling that can be utilized for both voice and data transmission. The use of two wires twisted together helps to reduce [[crosstalk (electronics)|crosstalk]] and [[electromagnetic induction]]. The transmission speed ranges from 2 million bits per second to 10 billion bits per second. Twisted pair cabling comes in two forms: unshielded twisted pair (UTP) and shielded twisted-pair (STP). Each form comes in several category ratings, designed for use in various scenarios.
*Coaxial cable is widely used for cable television systems, office buildings, and other work-sites for local area networks. The cables consist of copper or aluminum wire surrounded by an insulating layer (typically a flexible material with a high dielectric constant), which itself is surrounded by a conductive layer. The insulation between the conductors helps maintain the characteristic impedance of the cable which can help improve its performance. Transmission speed ranges from 200 million bits per second to more than 500 million bits per second.
*ITU-T G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network.
* Signal traces on printed circuit boards are common for board-level serial communication, particularly between certain types integrated circuits, a common example being SPI.
*Ribbon cable (untwisted and possibly unshielded) has been a cost-effective media for serial protocols, especially within metallic enclosures or rolled within copper braid or foil, over short distances, or at lower data rates. Several serial network protocols can be deployed without shielded or twisted pair cabling, that is, with "flat" or "ribbon" cable, or a hybrid flat/twisted ribbon cable, should EMC, length, and bandwidth constraints permit: RS-232,Cable Serial Male To Female 25L 4' DB25 M-DB25 28 AWG 300V Gray, Part no.: 12408, Jameco Electronics. RS-422, RS-485,AN-1057 Ten ways to bulletproof RS-485 Interfaces, Texas Instruments, p. 5. CAN,CANopen,CANopen DR-303 V1.0 Cabling and Connector Pin Assignment, CAN in Automation, p. 10. GPIB, SCSI,Advantech Co., Ltd., Cable 50-Pin SCSI Ribbon type # PCL-10152-3E (Mouser Electronics #923-PCL-10152-3E) etc.
*Twisted pair wire is the most widely used medium for all telecommunication. Twisted-pair cabling consist of copper wires that are twisted into pairs. Ordinary telephone wires consist of two insulated copper wires twisted into pairs. Computer network cabling (wired Ethernet as defined by IEEE 802.3) consists of 4 pairs of copper cabling that can be utilized for both voice and data transmission. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. The transmission speed ranges from 2 million bits per second to 10 billion bits per second. Twisted pair cabling comes in two forms: unshielded twisted pair (UTP) and shielded twisted-pair (STP). Each form comes in several category ratings, designed for use in various scenarios.
* 同轴电缆广泛用于有线电视系统、办公大楼和其他局域网工作场所。电缆由铜线或铝线组成，周围有一个绝缘层(通常是一种具有高介电常数的柔性材料) ，它本身被一个导电层包围。导体之间的绝缘有助于维持电缆的特性阻抗，从而有助于改善其性能。传输速度从每秒2亿比特到每秒5亿比特不等。
* ITU-T G.hn 技术利用现有的家庭布线(同轴电缆、电话线和电力线)创建高速(高达1Gigabit/s)的局域网。
* 印刷电路板上的信号痕迹在板级串行通信中很常见，特别是在某些类型的集成电路之间，一个常见的例子是 SPI。
* 带状电缆(未缠绕和可能未屏蔽)已成为串行协议的一种具有成本效益的介质，特别是在金属外壳内或在铜编织物或箔内轧制，短距离或以较低的数据速率。在电磁兼容、长度和带宽限制允许的情况下，可以部署几种串行网络协议，不需要屏蔽或双绞线缆，即使用“扁平”或“带状”电缆，或混合扁平/双绞带状电缆: RS-232，电缆串联男女25L 4’DB25 M-DB2528 AWG 300V Gray，Part No。翻译: 12408，Jameco Electronics Jameco Electronics。RS-422，RS-485，AN-1057防弹 RS-485接口的十种方法，德州仪器，第5页。CAN，CANopen，CANopen DR-303 V1.0布线和连接器插脚分配，CAN 在自动化，第10页。GPIB，SCSI，Advantech Co. ，Ltd. ，Cable 50-Pin SCSI 丝带型号 # PCL-10152-3E (Mouser Electronics # 923-PCL-10152-3E)等。
* 双绞线是所有电信中使用最广泛的媒介。双绞线电缆由铜线绞成双绞线组成。普通电话线由两根绝缘铜线绞成对组成。计算机网络布线(IEEE 802.3定义的有线以太网)由4对铜线组成，可用于语音和数据传输。使用双绞线有助于减少串音和电磁感应。传输速度从每秒200万比特到每秒100亿比特不等。双绞线有两种形式: 无屏蔽双绞线(UTP)和屏蔽双绞线(STP)。每个表单都有几个分类评级，设计用于各种场景。
[[File:World map of submarine cables.png|thumb|alt=World map with red and blue lines|2007 map showing submarine optical fiber telecommunication cables around the world.]]
*An ''[[optical fiber]]'' is a glass fiber. It carries pulses of light that represent data. Some advantages of optical fibers over metal wires are very low transmission loss and immunity from electrical interference. Optical fibers can simultaneously carry multiple wavelengths of light, which greatly increases the rate that data can be sent, and helps enable data rates of up to trillions of bits per second. Optic fibers can be used for long runs of cable carrying very high data rates, and are used for [[undersea cables]] to interconnect continents.
thumb|alt=World map with red and blue lines|2007 map showing submarine optical fiber telecommunication cables around the world.
*An optical fiber is a glass fiber. It carries pulses of light that represent data. Some advantages of optical fibers over metal wires are very low transmission loss and immunity from electrical interference. Optical fibers can simultaneously carry multiple wavelengths of light, which greatly increases the rate that data can be sent, and helps enable data rates of up to trillions of bits per second. Optic fibers can be used for long runs of cable carrying very high data rates, and are used for undersea cables to interconnect continents.
红色和蓝色线条的世界地图 | 2007年世界海底光纤通信电缆地图。光纤就是玻璃纤维
* 。它携带代表数据的光脉冲。与金属线相比，光纤的一些优点是传输损耗非常低，而且不会受到电干扰。光纤可以同时携带多种波长的光，这大大提高了数据的传输速率，并有助于使数据传输速率达到每秒数万亿比特。光纤可以用于长距离的电缆传输非常高的数据速率，也可以用于海底电缆连接大陆。
Price is a main factor distinguishing wired- and wireless-technology options in a business. Wireless options command a price premium that can make purchasing wired computers, printers and other devices a financial benefit. Before making the decision to purchase hard-wired technology products, a review of the restrictions and limitations of the selections is necessary. Business and employee needs may override any cost considerations.<ref>[http://smallbusiness.chron.com/disadvantages-wired-technology-17833.html], The Disadvantages of Wired Technology, Laura Acevedo, Demand Media.</ref>
Price is a main factor distinguishing wired- and wireless-technology options in a business. Wireless options command a price premium that can make purchasing wired computers, printers and other devices a financial benefit. Before making the decision to purchase hard-wired technology products, a review of the restrictions and limitations of the selections is necessary. Business and employee needs may override any cost considerations., The Disadvantages of Wired Technology, Laura Acevedo, Demand Media.
价格是区分企业有线和无线技术选择的一个主要因素。无线选择命令价格溢价，可以使购买有线电脑，打印机和其他设备的经济利益。在决定购买硬连线技术产品之前，有必要审查选择的限制和局限性。企业和员工的需求可能会压倒任何成本考虑因素，《有线技术的缺点》 ，劳拉 · 阿塞维多，《需求媒体》。
===Wireless technologies===
[[File:Wireless network.jpg|thumb|right|alt=Black laptop with router in the background |Personal computers are very often connected to networks using wireless links]]
{{Main|Wireless network}}
*''Terrestrial [[microwave]]'' – Terrestrial microwave communication uses Earth-based transmitters and receivers resembling satellite dishes. Terrestrial microwaves are in the low gigahertz range, which limits all communications to line-of-sight. Relay stations are spaced approximately {{convert|50|km|mi|abbr=on|sigfig=1}} apart.
*''[[Communications satellite]]s'' – Satellites communicate via microwave radio waves, which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically in [[geostationary orbit]] {{convert|35786|km|mi|abbr=on}} above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals.
*''[[Cellular network|Cellular]] and PCS systems'' use several radio communications technologies. The systems divide the region covered into multiple geographic areas. Each area has a low-power transmitter or radio relay antenna device to relay calls from one area to the next area.
*''Radio and [[spread spectrum]] technologies'' – Wireless local area networks use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANs use spread spectrum technology to enable communication between multiple devices in a limited area. [[IEEE 802.11]] defines a common flavor of open-standards wireless radio-wave technology known as [[Wi-Fi]].
*''[[Free-space optical communication]]'' uses visible or invisible light for communications. In most cases, [[line-of-sight propagation]] is used, which limits the physical positioning of communicating devices.
thumb|right|alt=Black laptop with router in the background |Personal computers are very often connected to networks using wireless links
*Terrestrial microwave – Terrestrial microwave communication uses Earth-based transmitters and receivers resembling satellite dishes. Terrestrial microwaves are in the low gigahertz range, which limits all communications to line-of-sight. Relay stations are spaced approximately apart.
*Communications satellites – Satellites communicate via microwave radio waves, which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically in geostationary orbit above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals.
*Cellular and PCS systems use several radio communications technologies. The systems divide the region covered into multiple geographic areas. Each area has a low-power transmitter or radio relay antenna device to relay calls from one area to the next area.
*Radio and spread spectrum technologies – Wireless local area networks use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANs use spread spectrum technology to enable communication between multiple devices in a limited area. IEEE 802.11 defines a common flavor of open-standards wireless radio-wave technology known as Wi-Fi.
*Free-space optical communication uses visible or invisible light for communications. In most cases, line-of-sight propagation is used, which limits the physical positioning of communicating devices.
= = = 无线技术 = = = 拇指 | 右边 | ALT = 黑色笔记本电脑，后台有路由器 | 个人电脑经常使用无线链路连接到网络
* 地面微波-地面微波通信使用类似卫星天线的地面发射机和接收机。地球上的微波是在低千兆赫的范围内，这限制了所有通信的视线。中继站之间的间隔大致相同。
* 通信卫星——卫星通过微波无线电波进行通信，这种无线电波不会被地球大气层偏转。这些卫星位于太空，通常位于赤道上方的地球静止轨道。这些地球轨道系统能够接收和中继语音、数据和电视信号。
* 蜂窝和 PCS 系统使用多种无线电通信技术。这些系统将覆盖的区域划分为多个地理区域。每个区域都有一个低功率发射机或无线电中继天线装置，用于将呼叫从一个区域转移到下一个区域。
* 无线电和扩频技术——无线局域网使用类似于数字蜂窝和低频无线电技术的高频无线电技术。无线局域网使用扩频技术在有限的区域内实现多个设备之间的通信。IEEE 802.11定义了一种称为 Wi-Fi 的开放标准无线电波技术。
* 自由空间光通信系统使用可见光或不可见光进行通讯。在大多数情况下，使用的是视线传播，这限制了通信设备的物理定位。
===Exotic technologies===
There have been various attempts at transporting data over exotic media:
There have been various attempts at transporting data over exotic media:
= = 外来技术 = = = 已经有多种尝试通过外来媒体传输数据:
* [[IP over Avian Carriers]] was a humorous April fool's [[Request for Comments]], issued as '''RFC 1149'''. It was implemented in real life in 2001.<ref>{{cite web|url=http://www.blug.linux.no/rfc1149 |title=Bergen Linux User Group's CPIP Implementation |publisher=Blug.linux.no |access-date=2014-03-01}}</ref>
* Extending the Internet to interplanetary dimensions via radio waves, the [[Interplanetary Internet]].<ref>{{citation |url=http://www.ipnsig.org/reports/ISART9-2000.pdf |archive-url=https://web.archive.org/web/20120113053223/http://www.ipnsig.org/reports/ISART9-2000.pdf |archive-date=2012-01-13 |title=Interplanetary Internet |publisher=Third Annual International Symposium on Advanced Radio Technologies |author=A. Hooke |date=September 2000 |access-date=2011-11-12}}</ref>
* IP over Avian Carriers was a humorous April fool's Request for Comments, issued as RFC 1149. It was implemented in real life in 2001.
* Extending the Internet to interplanetary dimensions via radio waves, the Interplanetary Internet.
* 信鸽IP通讯是一份幽默的愚人节评论请求，发行号为 RFC 1149。它于2001年在现实生活中实施。
* 透过无线电波将互联网扩展至星际空间，星际互联网。
Both cases have a large [[round-trip delay time]], which gives slow two-way communication, but doesn't prevent sending large amounts of information.
Both cases have a large round-trip delay time, which gives slow two-way communication, but doesn't prevent sending large amounts of information.
这两种情况都有一个很大的来回通讯延迟，可以进行缓慢的双向通信，但并不妨碍发送大量信息。
==Nodes==
{{Main|Node (networking)}}
Network nodes are the points of connection of the transmission medium to transmitters and receivers of the electrical, optical, or radio signals carried in the medium. Nodes may be associated with a computer, but certain types may have only a microcontroller at a node or possibly no programmable device at all. In the simplest of serial arrangements, one [[RS-232]] transmitter can be connected by a pair of wires to one receiver, forming two nodes on one link, or a Point-to-Point topology. Some protocols permit a single node to only either transmit or receive (e.g., [[ARINC 429]]). Other protocols have nodes that can both transmit and receive into a single channel (e.g., [[CANbus|CAN]] can have many transceivers connected to a single bus). While the conventional [[Systems engineering|system]] building blocks of a [[computer network]] include [[network interface controller]]s (NICs), [[repeater]]s, [[Ethernet hub|hubs]], [[Network bridge|bridges]], [[Network switch|switches]], [[Router (computing)|routers]], [[modem]]s, [[Gateway (telecommunications)|gateways]], and [[Firewall (computing)|firewalls]], most address network concerns beyond the physical network topology and may be represented as single nodes on a particular physical network topology.
Network nodes are the points of connection of the transmission medium to transmitters and receivers of the electrical, optical, or radio signals carried in the medium. Nodes may be associated with a computer, but certain types may have only a microcontroller at a node or possibly no programmable device at all. In the simplest of serial arrangements, one RS-232 transmitter can be connected by a pair of wires to one receiver, forming two nodes on one link, or a Point-to-Point topology. Some protocols permit a single node to only either transmit or receive (e.g., ARINC 429). Other protocols have nodes that can both transmit and receive into a single channel (e.g., CAN can have many transceivers connected to a single bus). While the conventional system building blocks of a computer network include network interface controllers (NICs), repeaters, hubs, bridges, switches, routers, modems, gateways, and firewalls, most address network concerns beyond the physical network topology and may be represented as single nodes on a particular physical network topology.
网络节点是介质与媒体上所载的电子、光学或无线电信号的发射机和接收机的连接点。节点可能与计算机相关联，但某些类型的节点上可能只有一个微控制器，或者可能根本没有可编程设备。在最简单的串行安排中，一个 RS-232发射机可以通过一对导线连接到一个接收机，在一个链路上形成两个节点，或者点对点拓扑。有些协议允许单个节点只发送或接收(例如 ARINC 429)。其他协议的节点可以同时发送和接收到单个信道(例如，CAN 可以将许多收发信机连接到单个总线)。虽然传统的计算机网络系统构建模块包括网络接口控制器(NICs)、中继器、集线器、桥接器、交换机、路由器、调制解调器、网关和防火墙，但大多数解决的网络问题超出了物理网络拓扑，可以表示为特定物理网络拓扑上的单个节点。
<!-- The following headings of Computer networking equipment are now possibly partially depreciated in this article, having been copied from [[Computer network]]. While these are indeed computer network building blocks, most provide services above the Physical Layer. Some headings can be modified to be inclusive of non-internet or non-Ethernet technologies specifically to address how they are relevant to (e.g., repeaters have long use in serial protocols, USB depends on Hubs). -->
===Network interfaces===
[[File:ForeRunnerLE 25 ATM Network Interface (1).jpg|thumb|right|alt=A network interface circuit with port for ATM|An [[Asynchronous Transfer Mode|ATM]] network interface in the form of an accessory card. A lot of network interfaces are built-in.]]
A [[network interface controller]] (NIC) is [[computer hardware]] that provides a computer with the ability to access the transmission media, and has the ability to process low-level network information. For example, the NIC may have a connector for accepting a cable, or an aerial for wireless transmission and reception, and the associated circuitry.
A network interface controller (NIC) is computer hardware that provides a computer with the ability to access the transmission media, and has the ability to process low-level network information. For example, the NIC may have a connector for accepting a cable, or an aerial for wireless transmission and reception, and the associated circuitry.
网络接口网卡是一种计算机硬件，它为计算机提供访问传输媒体的能力，并且具有处理低级网络信息的能力。例如，NIC 可能具有用于接收电缆的连接器，或用于无线传输和接收的天线，以及相关的电路。
The NIC responds to traffic addressed to a [[network address]] for either the NIC or the computer as a whole.
The NIC responds to traffic addressed to a network address for either the NIC or the computer as a whole.
网卡对网络地址的流量作出响应，无论是网卡还是计算机作为一个整体。
In [[Ethernet]] networks, each network interface controller has a unique [[MAC address|Media Access Control]] (MAC) address—usually stored in the controller's permanent memory. To avoid address conflicts between network devices, the [[Institute of Electrical and Electronics Engineers]] (IEEE) maintains and administers MAC address uniqueness. The size of an Ethernet MAC address is six [[Octet (computing)|octets]]. The three most significant octets are reserved to identify NIC manufacturers. These manufacturers, using only their assigned prefixes, uniquely assign the three least-significant octets of every Ethernet interface they produce.
In Ethernet networks, each network interface controller has a unique Media Access Control (MAC) address—usually stored in the controller's permanent memory. To avoid address conflicts between network devices, the Institute of Electrical and Electronics Engineers (IEEE) maintains and administers MAC address uniqueness. The size of an Ethernet MAC address is six octets. The three most significant octets are reserved to identify NIC manufacturers. These manufacturers, using only their assigned prefixes, uniquely assign the three least-significant octets of every Ethernet interface they produce.
在以太网中，每个网卡都有一个独特的媒体访问控制(Media Access Control，MAC)地址ーー通常存储在控制器的永久存储器中。为了避免网络设备之间的地址冲突，电气和电子工程师协会(IEEE)维护和管理 MAC 地址唯一性。以太网 MAC 地址的大小是六个八位。三个最重要的八位字节被保留用于识别 NIC 制造商。这些制造商只使用它们分配的前缀，唯一地分配它们生产的每个以太网接口的三个最不重要的八位元组。
===Repeaters and hubs===
A [[repeater]] is an [[Electronics|electronic]] device that receives a network [[signal (information theory)|signal]], cleans it of unnecessary noise and regenerates it. The signal may be reformed or [[retransmission (data networks)|retransmitted]] at a higher power level, to the other side of an obstruction possibly using a different transmission medium<!-- technically bridge-to-bridge -->, so that the signal can cover longer distances without degradation. Commercial repeaters have extended [[RS-232]] segments from 15 meters to over a kilometer.<ref>U.S. Converters, [http://www.usconverters.com/rs232-repeater-extender RS232 Repeater]</ref> In most twisted pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. With fiber optics, repeaters can be tens or even hundreds of kilometers apart.
A repeater is an electronic device that receives a network signal, cleans it of unnecessary noise and regenerates it. The signal may be reformed or retransmitted at a higher power level, to the other side of an obstruction possibly using a different transmission medium, so that the signal can cover longer distances without degradation. Commercial repeaters have extended RS-232 segments from 15 meters to over a kilometer.U.S. Converters, RS232 Repeater In most twisted pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. With fiber optics, repeaters can be tens or even hundreds of kilometers apart.
中继器和集线器中继器是一种接收网络信号，清除不必要的噪声并重新产生信号的电子设备。信号可以在较高的功率水平上重组或重新传输到障碍物的另一侧，可能使用不同的介质，这样信号可以覆盖更长的距离而不会降解。商用中继器已将 RS-232段从15米延长至1公里以上。转换器，RS232中继器在大多数双绞线以太网配置中，中继器是运行长度超过100米的电缆所必需的。使用光纤，中继器可以相距数十甚至数百公里。
Repeaters work within the physical layer of the OSI model, that is, there is no end-to-end change in the physical protocol across the repeater, or repeater pair, even if a different physical layer may be used between the ends of the repeater, or repeater pair. Repeaters require a small amount of time to regenerate the signal. This can cause a [[propagation delay]] that affects network performance and may affect proper function. As a result, many network architectures limit the number of repeaters that can be used in a row, e.g., the Ethernet [[5-4-3 rule]].
Repeaters work within the physical layer of the OSI model, that is, there is no end-to-end change in the physical protocol across the repeater, or repeater pair, even if a different physical layer may be used between the ends of the repeater, or repeater pair. Repeaters require a small amount of time to regenerate the signal. This can cause a propagation delay that affects network performance and may affect proper function. As a result, many network architectures limit the number of repeaters that can be used in a row, e.g., the Ethernet 5-4-3 rule.
中继器在 OSI 模型的物理层内工作，也就是说，即使在中继器或中继器对的两端之间可能使用不同的物理层，整个中继器或中继器对的物理协议也不会发生端到端的变化。中继器需要少量的时间来再生信号。这可能导致传播延迟影响网络性能，并可能影响正常功能。因此，许多网络架构限制了可以在一行中使用的中继器的数量，例如，以太网5-4-3规则。
A repeater with multiple ports is known as hub, an [[Ethernet hub]] in Ethernet networks, a [[USB hub]] in USB networks.
* [[USB]] networks use hubs to form tiered-star topologies.
* Ethernet hubs and repeaters in LANs have been mostly obsoleted by modern [[network switch|switches]].
A repeater with multiple ports is known as hub, an Ethernet hub in Ethernet networks, a USB hub in USB networks.
* USB networks use hubs to form tiered-star topologies.
* Ethernet hubs and repeaters in LANs have been mostly obsoleted by modern switches.
具有多个端口的中继器称为集线器，即以太网中的以太网集线器，USB 网中的 USB 集线器。
* USB 网络使用集线器形成分层星型拓扑。
* 局域网中的以太网集线器和中继器大多被现代交换机所淘汰。
===Bridges===
A [[network bridge]] connects and filters traffic between two [[network segment]]s at the [[data link layer]] (layer 2) of the [[OSI model]] to form a single network. This breaks the network's collision domain but maintains a unified broadcast domain. Network segmentation breaks down a large, congested network into an aggregation of smaller, more efficient networks.
A network bridge connects and filters traffic between two network segments at the data link layer (layer 2) of the OSI model to form a single network. This breaks the network's collision domain but maintains a unified broadcast domain. Network segmentation breaks down a large, congested network into an aggregation of smaller, more efficient networks.
在 OSI 模型的数据链路层(第二层) ，网桥连接并过滤两个网段之间的通信，从而形成一个单一的网络。这打破了网络的冲突域，但保持了一个统一的广播域。网络分割将一个大型拥挤的网络分解为一个更小、更有效的网络集合。
Bridges come in three basic types:
*Local bridges: Directly connect LANs
*Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers.
*Wireless bridges: Can be used to join LANs or connect remote devices to LANs.
Bridges come in three basic types:
*Local bridges: Directly connect LANs
*Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers.
*Wireless bridges: Can be used to join LANs or connect remote devices to LANs.
桥接器有三种基本类型:
* 本地桥接器: 直接连接局域网
* 远程桥接器: 可用于在局域网之间创建广域网(WAN)链接。远程桥接器，其中的连接链路比终端网络慢，很大程度上已经被路由器所取代。
* 无线桥接器: 可用于连接局域网或将远程设备连接到局域网。
===Switches===
A [[network switch]] is a device that forwards and filters [[OSI layer 2]] [[datagram]]s ([[Frame (networking)|frames]]) between [[Computer port (hardware)|ports]] based on the destination MAC address in each frame.<ref>{{cite web
|url=http://www.webopedia.com/TERM/s/switch.html
|title=Define switch.
|publisher=WWW.Wikipedia.com
|access-date=April 8, 2008
}}</ref>
A switch is distinct from a hub in that it only forwards the frames to the physical ports involved in the communication rather than all ports connected. It can be thought of as a multi-port bridge.<ref>{{cite web|url=http://compnetworking.about.com/cs/internetworking/g/bldef_bridge.htm|title=What bridge devices and bridging do for computer networks}}</ref> It learns to associate physical ports to MAC addresses by examining the source addresses of received frames. If an unknown destination is targeted, the switch broadcasts to all ports but the source. Switches normally have numerous ports, facilitating a star topology for devices, and cascading additional switches.
A network switch is a device that forwards and filters OSI layer 2 datagrams (frames) between ports based on the destination MAC address in each frame.
A switch is distinct from a hub in that it only forwards the frames to the physical ports involved in the communication rather than all ports connected. It can be thought of as a multi-port bridge. It learns to associate physical ports to MAC addresses by examining the source addresses of received frames. If an unknown destination is targeted, the switch broadcasts to all ports but the source. Switches normally have numerous ports, facilitating a star topology for devices, and cascading additional switches.
网络交换机是一种设备，它根据每帧中的目标 MAC 地址在端口之间转发和过滤 OSI 第2层数据报(帧)。交换机与集线器的区别在于，它只将帧转发给通信中涉及的物理端口，而不是所有连接的端口。它可以被认为是一个多端口的桥梁。它通过检查接收到的帧的源地址来学习将物理端口与 MAC 地址关联。如果目标是一个未知的目的地，交换机广播到所有端口，但源。交换机通常有许多端口，方便了设备的星型拓扑结构，并且级联了额外的交换机。
[[Network switch#Layer-specific functionality|Multi-layer switches]] are capable of routing based on layer 3 addressing or additional logical levels. The term ''switch'' is often used loosely to include devices such as routers and bridges, as well as devices that may distribute traffic based on load or based on application content (e.g., a Web [[Uniform Resource Locator|URL]] identifier).
Multi-layer switches are capable of routing based on layer 3 addressing or additional logical levels. The term switch is often used loosely to include devices such as routers and bridges, as well as devices that may distribute traffic based on load or based on application content (e.g., a Web URL identifier).
多层交换机能够基于第3层寻址或其他逻辑级别进行路由。交换机这个术语通常被广泛地用于包括路由器和桥接器等设备，以及可能根据负载或应用程序内容(例如，Web URL 标识符)分配流量的设备。
===Routers===
[[File:Adsl connections.jpg|thumb|right|A typical home or small office router showing the [[ADSL]] telephone line and [[Ethernet]] network cable connections]]
A [[Router (computing)|router]] is an [[internetworking]] device that forwards [[Packet (information technology)|packets]] between networks by processing the routing information included in the packet or datagram (Internet protocol information from layer 3). The routing information is often processed in conjunction with the [[routing table]] (or forwarding table). A router uses its routing table to determine where to forward packets. A destination in a routing table can include a "null" interface, also known as the "black hole" interface because data can go into it, however, no further processing is done for said data, i.e. the packets are dropped.
A router is an internetworking device that forwards packets between networks by processing the routing information included in the packet or datagram (Internet protocol information from layer 3). The routing information is often processed in conjunction with the routing table (or forwarding table). A router uses its routing table to determine where to forward packets. A destination in a routing table can include a "null" interface, also known as the "black hole" interface because data can go into it, however, no further processing is done for said data, i.e. the packets are dropped.
路由器是一种互联网设备，它通过处理包含在数据包或数据报中的路由信息(来自第3层的因特网协议信息)在网络之间转发数据包。路由信息通常与路由表(或转发表)一起处理。路由器使用其路由表来确定转发数据包的位置。路由表中的目的地可以包含一个“ null”接口，也称为“黑洞”接口，因为数据可以进入该接口，但是不会对所述数据进行进一步处理，即。数据包被丢弃了。
===Modems===
[[Modem]]s (MOdulator-DEModulator) are used to connect network nodes via wire not originally designed for digital network traffic, or for wireless. To do this one or more [[carrier signal]]s are [[modulation|modulated]] by the digital signal to produce an [[analog signal]] that can be tailored to give the required properties for transmission. Modems are commonly used for telephone lines, using a [[digital subscriber line]] technology.
Modems (MOdulator-DEModulator) are used to connect network nodes via wire not originally designed for digital network traffic, or for wireless. To do this one or more carrier signals are modulated by the digital signal to produce an analog signal that can be tailored to give the required properties for transmission. Modems are commonly used for telephone lines, using a digital subscriber line technology.
调制解调器(调制解调器)用于通过不是最初为数字网络流量或无线设计的有线连接网络节点。为此，一个或多个载波信号被数字信号调制以产生模拟信号，该模拟信号可以被调整以提供传输所需的特性。调制解调器通常用于电话线路，使用 DSL 技术。
===Firewalls===
A [[Firewall (computing)|firewall]] is a network device for controlling network security and access rules. Firewalls are typically configured to reject access requests from unrecognized sources while allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in [[cyberattack|cyber attack]]s.
A firewall is a network device for controlling network security and access rules. Firewalls are typically configured to reject access requests from unrecognized sources while allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in cyber attacks.
= = 防火墙 = = 防火墙是控制网络安全和访问规则的网络设备。防火墙通常配置为拒绝来自未识别源的访问请求，同时允许来自已识别源的操作。防火墙在网络安全中的重要作用与网络攻击的不断增加并行发展。
==Classification==
The study of network topology recognizes eight basic topologies: point-to-point, bus, star, ring or circular, mesh, tree, hybrid, or daisy chain.<ref name="Bicsi, B. 2002">{{cite book |author=Bicsi, B. |date=2002 |title=Network Design Basics for Cabling Professionals |publisher=McGraw-Hill Professional |isbn=9780071782968}}</ref>
The study of network topology recognizes eight basic topologies: point-to-point, bus, star, ring or circular, mesh, tree, hybrid, or daisy chain.
= = 分类 = = 网络拓扑的研究识别八种基本拓扑: 点对点、总线、星形、环形或圆形、网格、树形、混合或雏菊链。
===Point-to-point===
{{main article|Point-to-point (telecommunications)}}
The simplest topology with a dedicated link between two endpoints. Easiest to understand, of the variations of point-to-point topology, is a point-to-point [[communication channel]] that appears, to the user, to be permanently associated with the two endpoints. A child's [[tin can telephone]] is one example of a ''physical dedicated'' channel.
The simplest topology with a dedicated link between two endpoints. Easiest to understand, of the variations of point-to-point topology, is a point-to-point communication channel that appears, to the user, to be permanently associated with the two endpoints. A child's tin can telephone is one example of a physical dedicated channel.
= = = 点到点 = = = 最简单的拓扑，在两个端点之间有专用链接。对于点对点拓扑的变化，最容易理解的是一个点对点通信通道，在用户看来，它似乎与两个端点永久关联。儿童锡罐电话是一个物理专用频道的例子。
Using [[circuit-switching]] or [[packet-switching]] technologies, a point-to-point circuit can be set up dynamically and dropped when no longer needed. Switched point-to-point topologies are the basic model of conventional [[telephony]].
Using circuit-switching or packet-switching technologies, a point-to-point circuit can be set up dynamically and dropped when no longer needed. Switched point-to-point topologies are the basic model of conventional telephony.
使用电路交换或分组交换技术，点对点电路可以动态设置，并在不再需要时丢弃。点对点交换拓扑是传统电话的基本模型。
The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers and has been expressed as [[Metcalfe's Law]].
The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers and has been expressed as Metcalfe's Law.
永久性点对点网络的价值在于两个端点之间不受阻碍的通信。按需点对点连接的价值与潜在用户对的数量成正比，并被表示为梅特卡夫定律。
===Daisy chain===
[[Daisy chain (electrical engineering)|Daisy chaining]] is accomplished by connecting each computer in series to the next. If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination. A daisy-chained network can take two basic forms: linear and ring.
Daisy chaining is accomplished by connecting each computer in series to the next. If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination. A daisy-chained network can take two basic forms: linear and ring.
= = 雏菊链 = = 雏菊链是通过将每台计算机串联到下一台计算机来完成的。如果一条消息是打算发送给计算机的，那么每个系统都会按照顺序反弹它，直到它到达目的地。菊花链网络有两种基本形式: 线性网络和环状网络。
* A '''[[Linear bus topology|linear topology]]''' puts a two-way link between one computer and the next. However, this was expensive in the early days of computing, since each computer (except for the ones at each end) required two receivers and two transmitters.
* By connecting the computers at each end of the chain, a '''[[ring topology]]''' can be formed. When a [[Node (networking)|node]] sends a message, the message is processed by each computer in the ring. An advantage of the ring is that the number of transmitters and receivers can be cut in half. Since a message will eventually loop all of the way around, transmission does not need to go both directions. Alternatively, the ring can be used to improve fault tolerance. If the ring breaks at a particular link then the transmission can be sent via the reverse path thereby ensuring that all nodes are always connected in the case of a single failure.
* A linear topology puts a two-way link between one computer and the next. However, this was expensive in the early days of computing, since each computer (except for the ones at each end) required two receivers and two transmitters.
* By connecting the computers at each end of the chain, a ring topology can be formed. When a node sends a message, the message is processed by each computer in the ring. An advantage of the ring is that the number of transmitters and receivers can be cut in half. Since a message will eventually loop all of the way around, transmission does not need to go both directions. Alternatively, the ring can be used to improve fault tolerance. If the ring breaks at a particular link then the transmission can be sent via the reverse path thereby ensuring that all nodes are always connected in the case of a single failure.
* 线性拓扑在一台计算机和下一台计算机之间建立双向联系。然而，这在计算的早期是昂贵的，因为每台计算机(除了两端的计算机)需要两个接收器和两个发射器。
* 通过连接链条两端的计算机，可以形成环状拓扑结构。当节点发送消息时，环中的每台计算机都会处理该消息。这种环的一个优点是发射机和接收机的数量可以减少一半。由于信息最终会循环播放，所以传输不需要双向传播。或者，该环可用于提高容错性。如果环在一个特定的链路断开，那么传输可以通过反向路径发送，从而确保在单个故障的情况下所有节点总是连接在一起。
===Bus===
[[File:BusNetwork.svg|thumb|Bus network topology]]
{{Main article|Bus network}}
In local area networks using bus topology, each node is connected by interface connectors to a single central cable. This is the 'bus', also referred to as the [[Backbone network|backbone]], or [[Trunk (telecommunications)|trunk]] – all [[data transmission]] between nodes in the network is transmitted over this common transmission medium and is able to be [[Receiver (Information Theory)|received]] by all nodes in the network simultaneously.<ref name="Groth"/>
thumb|Bus network topology
In local area networks using bus topology, each node is connected by interface connectors to a single central cable. This is the 'bus', also referred to as the backbone, or trunk – all data transmission between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network simultaneously.
= = 总线 = = = 拇指 | 总线网络拓扑在使用总线拓扑的局域网中，每个节点通过接口连接器连接到一根中央电缆。这就是“总线”，也被称为骨干，或者干线——网络中的所有节点之间的数据传输都通过这个公共介质传输，并且能够被网络中的所有节点同时接收。
A signal containing the address of the intended receiving machine travels from a source machine in both directions to all machines connected to the bus until it finds the intended recipient, which then accepts the data. If the machine address does not match the intended address for the data, the data portion of the signal is ignored. Since the bus topology consists of only one wire it is less expensive to implement than other topologies, but the savings are offset by the higher cost of managing the network. Additionally, since the network is dependent on the single cable, it can be the [[single point of failure]] of the network. In this topology data being transferred may be accessed by any node.
A signal containing the address of the intended receiving machine travels from a source machine in both directions to all machines connected to the bus until it finds the intended recipient, which then accepts the data. If the machine address does not match the intended address for the data, the data portion of the signal is ignored. Since the bus topology consists of only one wire it is less expensive to implement than other topologies, but the savings are offset by the higher cost of managing the network. Additionally, since the network is dependent on the single cable, it can be the single point of failure of the network. In this topology data being transferred may be accessed by any node.
包含预定接收机地址的信号从源机向两个方向传播到连接到总线的所有机器，直到找到预定接收机，然后接受数据。如果机器地址与数据的预期地址不匹配，则忽略信号的数据部分。由于总线拓扑只包含一个线路，因此实现它的成本比其他拓扑要低，但是节省的成本被更高的网络管理成本所抵消。此外，由于网络依赖于单根电缆，它可以成为网络的单点故障。在此拓扑中，所传输的数据可由任何节点访问。
====Linear bus====
In a linear bus network, all of the nodes of the network are connected to a common transmission medium which has just two endpoints. When the electrical signal reaches the end of the bus, the signal is reflected back down the line, causing unwanted interference. To prevent this, the two endpoints of the bus are normally terminated with a device called a [[Electrical termination|terminator]].
In a linear bus network, all of the nodes of the network are connected to a common transmission medium which has just two endpoints. When the electrical signal reaches the end of the bus, the signal is reflected back down the line, causing unwanted interference. To prevent this, the two endpoints of the bus are normally terminated with a device called a terminator.
在线性总线网络中，网络的所有节点都连接到一个只有两个端点的公共介质上。当电信号到达总线末端时，信号沿着线路反射回去，造成不必要的干扰。为了防止这种情况，总线的两个端点通常用一个称为终止器的设备终止。
====Distributed bus====
In a distributed bus network, all of the nodes of the network are connected to a common transmission medium with more than two endpoints, created by adding branches to the main section of the transmission medium – the physical distributed bus topology functions in exactly the same fashion as the physical linear bus topology because all nodes share a common transmission medium.
In a distributed bus network, all of the nodes of the network are connected to a common transmission medium with more than two endpoints, created by adding branches to the main section of the transmission medium – the physical distributed bus topology functions in exactly the same fashion as the physical linear bus topology because all nodes share a common transmission medium.
分布式总线在一个分布式总线网络中，所有的网络节点都连接到一个具有两个以上端点的公共介质，这是通过在介质的主要部分添加分支而创建的——物理分布式总线拓扑功能与物理线性总线拓扑完全相同，因为所有节点都共享一个公共介质。
===Star===
{{Main article|Star network}}
[[File:StarNetwork.svg|thumb|Star network topology]]
In star topology, every peripheral node (computer workstation or any other peripheral) is connected to a central node called a hub or switch. The hub is the server and the peripherals are the clients. The network does not necessarily have to resemble a star to be classified as a star network, but all of the peripheral nodes on the network must be connected to one central hub. All traffic that traverses the network passes through the central hub, which acts as a [[Repeater|signal repeater]].
thumb|Star network topology
In star topology, every peripheral node (computer workstation or any other peripheral) is connected to a central node called a hub or switch. The hub is the server and the peripherals are the clients. The network does not necessarily have to resemble a star to be classified as a star network, but all of the peripheral nodes on the network must be connected to one central hub. All traffic that traverses the network passes through the central hub, which acts as a signal repeater.
星型网络拓扑在星型拓扑中，每个外围节点(计算机工作站或任何其他外围节点)都连接到一个称为集线器或交换机的中心节点。集线器是服务器，外围设备是客户机。网络不一定要像一颗星才能被归类为星型网络，但是网络上的所有外围节点必须连接到一个中心枢纽。所有穿过网络的流量都要经过中心枢纽，中心枢纽起到信号中继器的作用。
The star topology is considered the easiest topology to design and implement. One advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure. Also, since all peripheral communication must flow through the central hub, the aggregate central bandwidth forms a network bottleneck for large clusters.
The star topology is considered the easiest topology to design and implement. One advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure. Also, since all peripheral communication must flow through the central hub, the aggregate central bandwidth forms a network bottleneck for large clusters.
星型拓扑被认为是最容易设计和实现的拓扑。星型拓扑的一个优点是添加额外节点的简单性。星型拓扑的主要缺点是中心代表单点故障。而且，由于所有外围通信都必须通过中央集线器，因此聚合的中央带宽对于大型集群来说形成了网络瓶颈。
====Extended star====
The extended star network topology extends a physical star topology by one or more repeaters between the central node and the [[peripheral]] (or 'spoke') nodes. The repeaters are used to extend the maximum transmission distance of the physical layer, the point-to-point distance between the central node and the peripheral nodes. Repeaters allow greater transmission distance, further than would be possible using just the transmitting power of the central node. The use of repeaters can also overcome limitations from the standard upon which the physical layer is based.
The extended star network topology extends a physical star topology by one or more repeaters between the central node and the peripheral (or 'spoke') nodes. The repeaters are used to extend the maximum transmission distance of the physical layer, the point-to-point distance between the central node and the peripheral nodes. Repeaters allow greater transmission distance, further than would be possible using just the transmitting power of the central node. The use of repeaters can also overcome limitations from the standard upon which the physical layer is based.
扩展星型扩展星型网络拓扑在中央节点和外围(或“辐射”)节点之间通过一个或多个中继器扩展物理星型拓扑。中继器用于延长物理层的最大传输距离、中心节点与外围节点之间的点对点距离。中继器允许更大的传输距离，比仅仅使用中心节点的传输功率可能达到的距离更远。中继器的使用还可以克服物理层所基于的标准的局限性。
A physical extended star topology in which repeaters are replaced with hubs or switches is a type of hybrid network topology and is referred to as a physical hierarchical star topology, although some texts make no distinction between the two topologies.
A physical extended star topology in which repeaters are replaced with hubs or switches is a type of hybrid network topology and is referred to as a physical hierarchical star topology, although some texts make no distinction between the two topologies.
物理扩展星形拓扑，其中中继器被集线器或交换机取代，是一种混合网络拓扑，被称为物理层次星形拓扑，尽管一些文本没有区分这两种拓扑。
A physical hierarchical star topology can also be referred as a tier-star topology, this topology differs from a [[tree topology]] in the way star networks are connected together. A tier-star topology uses a central node, while a tree topology uses a central bus and can also be referred as a star-bus network.
A physical hierarchical star topology can also be referred as a tier-star topology, this topology differs from a tree topology in the way star networks are connected together. A tier-star topology uses a central node, while a tree topology uses a central bus and can also be referred as a star-bus network.
物理层次星型拓扑也可以称为层次星型拓扑，这种拓扑在星型网络连接方式上不同于树型拓扑。层星型拓扑使用中心节点，而树型拓扑使用中心总线，也可以称为星型总线网络。
====Distributed star====
A distributed star is a network topology that is composed of individual networks that are based upon the physical star topology connected in a linear fashion – i.e., 'daisy-chained' – with no central or top level connection point (e.g., two or more 'stacked' hubs, along with their associated star connected nodes or 'spokes').
A distributed star is a network topology that is composed of individual networks that are based upon the physical star topology connected in a linear fashion – i.e., 'daisy-chained' – with no central or top level connection point (e.g., two or more 'stacked' hubs, along with their associated star connected nodes or 'spokes').
分布式星型是一种由单个网络组成的网络拓扑，这些网络基于物理星型拓扑结构，以线性方式连接——例如，“菊花链”——没有中央或顶层连接点(例如，两个或多个“堆叠”集线器，以及它们相关的星型连接节点或“辐条”)。
===Ring===
{{Main article|Ring network}}
[[File:RingNetwork.svg|thumb|Ring network topology]]
thumb|Ring network topology
= = 戒指 = = = 拇指 | 戒指网络拓扑
A ring topology is a [[Daisy chain (electrical engineering)|daisy chain]] in a closed loop. Data travels around the ring in one direction. When one node sends data to another, the data passes through each intermediate node on the ring until it reaches its destination. The intermediate nodes repeat (retransmit) the data to keep the signal strong.<ref name="Inc, S. 2002"/> Every node is a peer; there is no hierarchical relationship of clients and servers. If one node is unable to retransmit data, it severs communication between the nodes before and after it in the bus.
A ring topology is a daisy chain in a closed loop. Data travels around the ring in one direction. When one node sends data to another, the data passes through each intermediate node on the ring until it reaches its destination. The intermediate nodes repeat (retransmit) the data to keep the signal strong. Every node is a peer; there is no hierarchical relationship of clients and servers. If one node is unable to retransmit data, it severs communication between the nodes before and after it in the bus.
环拓扑是闭环中的菊花链。数据沿着环的一个方向传播。当一个节点向另一个节点发送数据时，数据通过环上的每个中间节点，直到到达目的地。中间节点重复(重新传输)数据以保持信号强大。每个节点都是一个对等节点; 客户端和服务器之间没有层次关系。如果一个节点无法重新传输数据，它将在总线中切断节点之前和之后的通信。
Advantages:
* When the load on the network increases, its performance is better than bus topology.
* There is no need of network server to control the connectivity between workstations.
Advantages:
* When the load on the network increases, its performance is better than bus topology.
* There is no need of network server to control the connectivity between workstations.
优点:
* 当网络负载增加时，其性能优于总线拓扑。
* 不需要网络服务器来控制工作站之间的连接。
Disadvantages:
* Aggregate network bandwidth is bottlenecked by the weakest link between two nodes.
Disadvantages:
* Aggregate network bandwidth is bottlenecked by the weakest link between two nodes.
缺点:
* 聚合网络带宽受到两个节点之间最弱链接的瓶颈。
===Mesh===
{{Main article|Mesh networking}}
The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints, is approximated by [[Reed's Law]].
The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints, is approximated by Reed's Law.
假设任意两个端点(包括所有端点)的通信组都近似于里德定律，那么完全网状网络的价值与用户数的指数成正比。
====Fully connected network====
[[File:NetworkTopology-FullyConnected.png|thumb|Fully connected mesh topology]]
thumb|Fully connected mesh topology
= = = 完全连接的网络 = = = = 拇指 | 完全连接的网格拓扑
In a ''fully connected network'', all nodes are interconnected. (In [[graph theory]] this is called a [[complete graph]].) The simplest fully connected network is a two-node network. A fully connected network doesn't need to use [[packet switching]] or [[Broadcasting (networks)|broadcasting]]. However, since the number of connections grows quadratically with the number of nodes:
In a fully connected network, all nodes are interconnected. (In graph theory this is called a complete graph.) The simplest fully connected network is a two-node network. A fully connected network doesn't need to use packet switching or broadcasting. However, since the number of connections grows quadratically with the number of nodes:
在一个完全连接的网络中，所有的节点都是相互连接的。(在图论中，这叫做完全图。)最简单的完全连接网络是两节点网络。一个完全连接的网络不需要使用分组交换或广播。然而，由于连接的数量与节点的数量成二次增长:
<math>c= \frac{n(n-1)}{2}.\,</math>
c= \frac{n(n-1)}{2}.\,
C = frac { n (n-1)}{2},
This makes it impractical for large networks. This kind of topology does not trip and affect other nodes in the network.
This makes it impractical for large networks. This kind of topology does not trip and affect other nodes in the network.
这使得它不适用于大型网络。这种拓扑结构不会跳闸，也不会影响网络中的其他节点。
====Partially connected network====
[[File:NetworkTopology-Mesh.svg|thumb|Partially connected mesh topology]]
In a partially connected network, certain nodes are connected to exactly one other node; but some nodes are connected to two or more other nodes with a point-to-point link. This makes it possible to make use of some of the redundancy of mesh topology that is physically fully connected, without the expense and complexity required for a connection between every node in the network.
thumb|Partially connected mesh topology
In a partially connected network, certain nodes are connected to exactly one other node; but some nodes are connected to two or more other nodes with a point-to-point link. This makes it possible to make use of some of the redundancy of mesh topology that is physically fully connected, without the expense and complexity required for a connection between every node in the network.
部分连接网络在部分连接的网络中，某些节点恰好连接到另一个节点; 但是有些节点通过点对点链接连接到两个或更多的其他节点。这使得利用物理上完全连接的网格拓扑的一些冗余成为可能，而不需要在网络中的每个节点之间建立连接所需的开销和复杂性。
===Hybrid===
Hybrid topology is also known as hybrid network.<ref>{{Cite web|title=What is Hybrid Topology ? Advantages and Disadvantages|url=http://www.orosk.com/hybrid-topology/|url-status=dead|archive-url=https://web.archive.org/web/20160909170820/http://www.orosk.com/hybrid-topology/|archive-date=September 9, 2016|access-date=2018-01-26|website=OROSK.COM|language=en-US}}</ref> Hybrid networks combine two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a [[tree network]] (or ''star-bus network'') is a hybrid topology in which [[star network]]s are interconnected via [[bus network]]s.<ref name="Sosinsky">{{cite book |title=Networking Bible |last=Sosinsky |first=Barrie A. |page=16 |date=2009 |location=Indianapolis |publisher=Wiley Publishing |isbn=978-0-470-43131-3 |oclc=359673774 |chapter=Network Basics |chapter-url=https://books.google.com/books?id=3DOREqRZejcC&pg=PA16 |access-date=2016-03-26}}</ref><ref>{{cite book |url=https://books.google.com/books?id=gnuwPpBcO-MC&pg=RA1-PT12 |title=Understanding Computer Science (for Advanced Level): The Study Guide |last=Bradley |first=Ray |location=Cheltenham |publisher=[[Nelson Thornes]] |page=244 |isbn=978-0-7487-6147-0 |oclc=47869750 |access-date=2016-03-26|year=2001 }}</ref> However, a tree network connected to another tree network is still topologically a tree network, not a distinct network type. A hybrid topology is always produced when two different basic network topologies are connected.
Hybrid topology is also known as hybrid network. Hybrid networks combine two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network (or star-bus network) is a hybrid topology in which star networks are interconnected via bus networks. However, a tree network connected to another tree network is still topologically a tree network, not a distinct network type. A hybrid topology is always produced when two different basic network topologies are connected.
混合拓扑也称为混合网络。混合网络将两种或多种拓扑结合在一起，使得得到的网络不会显示出其中一种标准拓扑(例如，总线、星形、环形等)。例如，树形网络(或星形总线网络)是一种混合拓扑结构，其中星形网络通过总线网络相互连接。然而，一个树状网络连接到另一个树状网络，在拓扑上仍然是一个树状网络，而不是一个独特的网络类型。当两个不同的基本网络拓扑相互连接时，总会产生混合拓扑。
A ''star-ring'' network consists of two or more ring networks connected using a [[Media Access Unit|multistation access unit]] (MAU) as a centralized hub.
A star-ring network consists of two or more ring networks connected using a multistation access unit (MAU) as a centralized hub.
星环网络由两个或多个环网组成，环网使用多站接入单元(MAU)作为集中的集线器连接。
Snowflake topology is a star network of star networks.{{citation needed|date=March 2016}}
Snowflake topology is a star network of star networks.
雪花拓扑是由星形网络组成的星形网络。
Two other hybrid network types are ''hybrid mesh'' and ''hierarchical star''.<ref name="Sosinsky"/>
Two other hybrid network types are hybrid mesh and hierarchical star.
另外两种混合网络类型是混合网格和层次星型。
==Centralization==
The '''[[Star network|star topology]]''' reduces the probability of a network failure by connecting all of the peripheral nodes (computers, etc.) to a central node. When the physical star topology is applied to a logical bus network such as [[Ethernet]], this central node (traditionally a hub) rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All [[peripheral]] nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The [[failure]] of a [[transmission line]] linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the remaining peripheral nodes will be unaffected. However, the disadvantage is that the failure of the central node will cause the failure of all of the peripheral nodes.
The star topology reduces the probability of a network failure by connecting all of the peripheral nodes (computers, etc.) to a central node. When the physical star topology is applied to a logical bus network such as Ethernet, this central node (traditionally a hub) rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the remaining peripheral nodes will be unaffected. However, the disadvantage is that the failure of the central node will cause the failure of all of the peripheral nodes.
星型拓扑通过连接所有的外围节点(计算机等)来降低网络故障的可能性一个中心节点。当将物理星型拓扑应用于逻辑总线网络(例如以太网)时，这个中心节点(传统上是集线器)将从任何外围节点接收到的所有传输重新广播到网络上的所有外围节点，有时包括原始节点。因此，所有外围节点可以通过仅向中心节点发送和从中心节点接收而与所有其他节点通信。如果连接任何外围节点到中央节点的传输线发生故障，将导致该外围节点与所有其他节点隔离，但其余的外围节点将不受影响。然而，缺点是中心节点的故障将导致所有外围节点的故障。
If the central node is ''passive'', the originating node must be able to tolerate the reception of an [[Echo (phenomenon)|echo]] of its own transmission, delayed by the two-way [[round-trip time|round trip]] [[transmission time]] (i.e. to and from the central node) plus any delay generated in the central node. An ''active'' star network has an active central node that usually has the means to prevent echo-related problems.
If the central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way round trip transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems.
如果中心节点是被动的，则发起节点必须能够容忍其自身传输的回波的接收，这种回波被双向往返传输时间(即。中心节点)加上中心节点中产生的任何延迟。主动星形网络有一个主动中心节点，该节点通常具有防止回波相关问题的手段。
A '''[[tree topology]]''' (a.k.a. '''hierarchical topology''') can be viewed as a collection of star networks arranged in a [[hierarchy]]. This [[tree structure]] has individual peripheral nodes (e.g. leaves) which are required to transmit to and receive from one other node only and are not required to act as repeaters or regenerators. Unlike the star network, the functionality of the central node may be distributed.
A tree topology (a.k.a. hierarchical topology) can be viewed as a collection of star networks arranged in a hierarchy. This tree structure has individual peripheral nodes (e.g. leaves) which are required to transmit to and receive from one other node only and are not required to act as repeaters or regenerators. Unlike the star network, the functionality of the central node may be distributed.
树拓扑(又名。层次拓扑结构)可以看作是一个星形网络的集合，按层次结构排列。这个树结构有单独的外围节点(例如。只需要向另一个节点发送和从另一个节点接收，而不需要作为中继器或再生器。与星形网络不同，中心节点的功能可以分布式实现。
As in the conventional star network, individual nodes may thus still be isolated from the network by a single-point failure of a transmission path to the node. If a link connecting a leaf fails, that leaf is isolated; if a connection to a non-leaf node fails, an entire section of the network becomes isolated from the rest.
As in the conventional star network, individual nodes may thus still be isolated from the network by a single-point failure of a transmission path to the node. If a link connecting a leaf fails, that leaf is isolated; if a connection to a non-leaf node fails, an entire section of the network becomes isolated from the rest.
与传统的星型网络一样，单个节点仍然可以通过传输路径的单点故障从网络中隔离出来。如果连接叶子的链接失败，那么叶子将被隔离; 如果连接到非叶子节点失败，则网络的整个部分将与其余部分隔离。
To alleviate the amount of network traffic that comes from broadcasting all signals to all nodes, more advanced central nodes were developed that are able to keep track of the identities of the nodes that are connected to the network. These [[network switch]]es will "learn" the layout of the network by "listening" on each port during normal data transmission, examining the [[data packets]] and recording the address/identifier of each connected node and which port it is connected to in a [[lookup table]] held in memory. This lookup table then allows future transmissions to be forwarded to the intended destination only.
To alleviate the amount of network traffic that comes from broadcasting all signals to all nodes, more advanced central nodes were developed that are able to keep track of the identities of the nodes that are connected to the network. These network switches will "learn" the layout of the network by "listening" on each port during normal data transmission, examining the data packets and recording the address/identifier of each connected node and which port it is connected to in a lookup table held in memory. This lookup table then allows future transmissions to be forwarded to the intended destination only.
为了减少向所有节点广播所有信号产生的网络流量，开发了更先进的中央节点，能够跟踪连接到网络的节点的身份。这些网络交换机会在正常数据传输时“监听”每个端口，检查数据包，并记录每个连接节点的地址/标识符，以及该节点连接到内存中的查找表中的哪个端口，从而“学习”网络的布局。这个查找表只允许将来的传输转发到预期的目的地。
==Decentralization==
In a partially connected mesh topology, there are at least two nodes with two or more paths between them to provide redundant paths in case the link providing one of the paths fails. Decentralization is often used to compensate for the single-point-failure disadvantage that is present when using a single device as a central node (e.g., in star and tree networks). A special kind of mesh, limiting the number of hops between two nodes, is a [[hypercube]]. The number of arbitrary forks in mesh networks makes them more difficult to design and implement, but their decentralized nature makes them very useful.
In a partially connected mesh topology, there are at least two nodes with two or more paths between them to provide redundant paths in case the link providing one of the paths fails. Decentralization is often used to compensate for the single-point-failure disadvantage that is present when using a single device as a central node (e.g., in star and tree networks). A special kind of mesh, limiting the number of hops between two nodes, is a hypercube. The number of arbitrary forks in mesh networks makes them more difficult to design and implement, but their decentralized nature makes them very useful.
= = 地方分权 = = 在一个部分连接的网格拓扑结构中，至少有两个节点之间有两条或多条路径，以便在提供其中一条路径的链路出现故障时提供冗余路径。地方分权通常用来弥补单一设备作为中心节点时出现的单点故障缺陷(例如，在星型和树型网络中)。一种特殊的网格类型是超立方体，它限制两个节点之间的跳数。网状网络中任意分叉的数量使得它们的设计和实现更加困难，但是它们的分散性使得它们非常有用。
This is similar in some ways to a [[grid network]], where a linear or ring topology is used to connect systems in multiple directions. A multidimensional ring has a [[torus|toroidal]] topology, for instance.
This is similar in some ways to a grid network, where a linear or ring topology is used to connect systems in multiple directions. A multidimensional ring has a toroidal topology, for instance.
这在某些方面类似于网格网络，其中使用线性或环形拓扑将多个方向的系统连接起来。例如，多维环具有环形拓扑结构。
A ''fully connected network'', ''complete topology'', or ''full mesh topology'' is a network topology in which there is a direct link between all pairs of nodes. In a fully connected network with n nodes, there are <math>\frac{n(n-1)}{2}\,</math> direct links. Networks designed with this topology are usually very expensive to set up, but provide a high degree of reliability due to the multiple paths for data that are provided by the large number of redundant links between nodes. This topology is mostly seen in [[military]] applications.
A fully connected network, complete topology, or full mesh topology is a network topology in which there is a direct link between all pairs of nodes. In a fully connected network with n nodes, there are \frac{n(n-1)}{2}\, direct links. Networks designed with this topology are usually very expensive to set up, but provide a high degree of reliability due to the multiple paths for data that are provided by the large number of redundant links between nodes. This topology is mostly seen in military applications.
完全连接的网络、完全拓扑或完全网状拓扑是一种网络拓扑，其中所有节点对之间都有直接链接。在具有 n 个节点的完全连通网络中，存在 frc { n (n-1)}{2}直接链路。使用这种拓扑结构设计的网络通常建立起来非常昂贵，但是由于节点之间大量冗余链路为数据提供了多条路径，因此提供了高度的可靠性。这种拓扑结构主要用于军事应用程序。
==See also==
{{div col|colwidth=20em}}
* [[Broadcast communication network]]
* [[Butterfly network]]
* [[Computer network diagram]]
* [[Gradient network]]
* [[Internet topology]]
* [[Network simulation]]
* [[Relay network]]
* [[Rhizome (philosophy)]]
* [[Scale-free network]]
* [[Shared mesh]]
* [[Switched communication network]]
* [[Switched mesh]]
{{div col end}}
* Broadcast communication network
* Butterfly network
* Computer network diagram
* Gradient network
* Internet topology
* Network simulation
* Relay network
* Rhizome (philosophy)
* Scale-free network
* Shared mesh
* Switched communication network
* Switched mesh
* 广播通信网络
* 蝴蝶网络
* 网路图
* 互联网拓扑
* 网络仿真
* 中继网络
* 根无尺度网络
* 共享网络
* 交换通信网络
* 交换网络
==References==
{{Reflist}}
==External links==
{{Commons|Topology (Network)}}
* [https://web.archive.org/web/20141106222358/http://www.nyu.edu/its/pubs/architecture/kyriannis-tetrahedroncore.pdf Tetrahedron Core Network:] Application of a tetrahedral structure to create a resilient partial-mesh 3-dimensional campus backbone data network
* Tetrahedron Core Network: Application of a tetrahedral structure to create a resilient partial-mesh 3-dimensional campus backbone data network
= = 外部链接 = =
* 四面体核心网: 应用四面体结构创建弹性局部网格三维校园主干数据网
{{Network topologies}}
{{DEFAULTSORT:Network topology}}
[[Category:Network topology| ]]
[[Category:Decentralization]]
Category:Decentralization
分类: 地方分权
<noinclude>
<small>This page was moved from [[wikipedia:en:Network topology]]. Its edit history can be viewed at [[网络拓扑/edithistory]]</small></noinclude>
[[Category:待整理页面]]