Router: Difference between revisions
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[[File:SPOF.png|thumb|Computers connected to a server using a router]] |
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[[file:ERS-8600.JPG|thumb|150px|right|[[Avaya]] ERS-8600]] |
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A '''router''' is a [[computer]] whose [[software]] and [[Computer hardware|hardware]] are designed to move data between [[Computer network|computer networks]]. Routers move traffic to where it needs to go. They do this by choosing the shortest path between the computers using a complicated system of rules called [[routing protocol]]s. Most routers have a specialized [[operating system]], [[random access memory|RAM]], [[NVRAM]], [[flash memory]], and one or more [[central processing unit|processors]]. They also have two or more [[network card|network interface]]s. They come in a variety of sizes from something that could hold in the hand to something too large for one person to lift. |
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A router is a computer networking device that determines the next network point to which a data packet should be forwarded toward its destination, a process known as routing. Routing occurs at layer 3 of the OSI seven-layer model. |
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Routing is most commonly associated with the Internet protocol, although other less popular routed protocols are still in use. |
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If a computer has an connection to the [[Internet]], It is connected to a router that the computer sends data to. This is the first router the computer will connect to in order to get to the internet. It is known as a [[default gateway]] because it is the gateway to the internet. By convention, the gateway has the lowest [[IP address]] (like a phone number for a computer) in the [[subnet]] (a group of addresses). Anytime a computer makes a connection (such as a connection to www.wikipedia.org), the IP address of the destination server is found using a service called [[Domain Name System|DNS]] ([[Domain Name System]]). Once the destination address has been found, the computer connects to the gateway router. The gateway then sends data to a router at the [[Internet service provider|ISP]] ([[Internet service provider|Internet Service Provider]]). That router is a part of the internet and connects to other routers until the data reaches the destination. |
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The original 1960s-era routers were general-purpose computers. Although general-purpose computers can be used for routing, modern high-speed routers are highly specialised computers, generally with extra hardware added to accelerate the common routing functions, such as packet forwarding. |
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[[File:Belkin Wireless G Router F5D7231-4 Version 1000de-1121.jpg|left|thumb|Small router with [[Wi-Fi|WiFi]] built in.]] |
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Other changes are also made to improve reliability, such as using battery rather than main power, and using solid-state rather than magnetic storage. Modern routers have thus come to resemble telephone switches, which technology they are currently converging with and may eventually replace. |
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In small networks such as homes, small businesses (including [[internet café]]s) and small schools, the router also performs [[Network address translation|NAT]] (network address translation) which makes all outgoing connections look like they come from one address. Typically, incoming connections are only allowed if they are replies to connections made by a computer inside the NAT. |
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A router must be connected to at least two networks, or it will have nothing to route. A special variety of router is the one-armed router[?] used to route packets in a virtual LAN environment. In the case of a one-armed router the multiple attachments to different networks are all over the same physical link. |
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A router creates and/or maintains a table, called a "routing table" that stores the best routes to certain network destinations and the "routing metrics" associated with those routes. See the routing article for a more detailed discussion of how this works. |
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Routers connect two or more networks and direct traffic between them. These networks may be physical (the network is associated with a port) or logical (not associated with a port on the router).<ref>[ftp://ftp.rfc-editor.org/in-notes/rfc1812.txt Requirements for IPv4 Routers],[[RFC:1812|RFC 1812]], F. Baker,June 1995</ref> The term '''layer 3 switch''' often is used the same as 'router', but it is a general term without a technical definition. Layer 3 switch implies a device that is built to connect [[Ethernet]] devices in a [[LAN]] but can also perform routing. |
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Router operating systems are split into two parts:<ref>[rfc:3654 Requirements for Separation of IP Control and Forwarding],[[RFC:3654|RFC 3654]], H. Khosravi & T. Anderson,November 2003</ref> |
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* The [[Control Plane]], where the router learns the best port to send data to for a specific destination |
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* The [[Forwarding Plane]], where the router does the work of sending data to its destination. |
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==Related pages== |
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* [[Internet protocol suite]] |
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* [[Communications protocol]] |
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== References == |
== References == |
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{{Reflist}} |
{{Reflist}} |
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{{stub}} |
{{tech-stub}} |
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[[Category:Computer networking| ]] |
[[Category:Computer networking| ]] |
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[[Category:Internet]] |
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Latest revision as of 18:37, 16 March 2024
A router is a computer whose software and hardware are designed to move data between computer networks. Routers move traffic to where it needs to go. They do this by choosing the shortest path between the computers using a complicated system of rules called routing protocols. Most routers have a specialized operating system, RAM, NVRAM, flash memory, and one or more processors. They also have two or more network interfaces. They come in a variety of sizes from something that could hold in the hand to something too large for one person to lift.
If a computer has an connection to the Internet, It is connected to a router that the computer sends data to. This is the first router the computer will connect to in order to get to the internet. It is known as a default gateway because it is the gateway to the internet. By convention, the gateway has the lowest IP address (like a phone number for a computer) in the subnet (a group of addresses). Anytime a computer makes a connection (such as a connection to www.wikipedia.org), the IP address of the destination server is found using a service called DNS (Domain Name System). Once the destination address has been found, the computer connects to the gateway router. The gateway then sends data to a router at the ISP (Internet Service Provider). That router is a part of the internet and connects to other routers until the data reaches the destination.
In small networks such as homes, small businesses (including internet cafés) and small schools, the router also performs NAT (network address translation) which makes all outgoing connections look like they come from one address. Typically, incoming connections are only allowed if they are replies to connections made by a computer inside the NAT.
Routers connect two or more networks and direct traffic between them. These networks may be physical (the network is associated with a port) or logical (not associated with a port on the router).[1] The term layer 3 switch often is used the same as 'router', but it is a general term without a technical definition. Layer 3 switch implies a device that is built to connect Ethernet devices in a LAN but can also perform routing.
Router operating systems are split into two parts:[2]
- The Control Plane, where the router learns the best port to send data to for a specific destination
- The Forwarding Plane, where the router does the work of sending data to its destination.
Related pages[change | change source]
References[change | change source]
- ↑ Requirements for IPv4 Routers,RFC 1812, F. Baker,June 1995
- ↑ [rfc:3654 Requirements for Separation of IP Control and Forwarding],RFC 3654, H. Khosravi & T. Anderson,November 2003
