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Q: Routing Algorithms ( Answered,   0 Comments )
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 Subject: Routing Algorithms Category: Computers Asked by: georkir-ga List Price: \$4.50 Posted: 15 May 2004 05:11 PDT Expires: 14 Jun 2004 05:11 PDT Question ID: 346726
 Types of Interworking Routing Algorithms
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 Subject: Re: Routing Algorithms Answered By: andrewxmp-ga on 15 May 2004 21:07 PDT
 Hi, The two main types of routing algorithms used for directing network traffic are all dynamic in nature in that they are constntly updating based on new address information. I excerpted some of the content, but I suggest you visit the linked sites for a good primer on these algorithms. The main types of dynamic algorithms are introduced at at: [ http://computer.howstuffworks.com/routing-algorithm1.htm ] "Based on how routers gather information about the structure of a network and their analysis of information to specify the best route, we have two major routing algorithms: global routing algorithms and decentralized routing algorithms. In decentralized routing algorithms, each router has information about the routers it is directly connected to -- it doesn't know about every router in the network. These algorithms are also known as DV (distance vector) algorithms. In global routing algorithms, every router has complete information about all other routers in the network and the traffic status of the network. These algorithms are also known as LS (link state) algorithms." "Link state" algorithms are further discussed at: [ http://computer.howstuffworks.com/routing-algorithm2.htm ] "In LS algorithms, every router has to follow these steps: Identify the routers that are physically connected to them and get their IP addresses When a router starts working, it first sends a "HELLO" packet over network. Each router that receives this packet replies with a message that contains its IP address. Measure the delay time (or any other important parameters of the network, such as average traffic) for neighbor routers In order to do that, routers send echo packets over the network. Every router that receives these packets replies with an echo reply packet. By dividing round trip time by 2, routers can count the delay time. (Round trip time is a measure of the current delay on a network, found by timing a packet bounced off some remote host.) Note that this time includes both transmission and processing times -- the time it takes the packets to reach the destination and the time it takes the receiver to process it and reply. Broadcast its information over the network for other routers and receive the other routers' information In this step, all routers share their knowledge and broadcast their information to each other. In this way, every router can know the structure and status of the network. Using an appropriate algorithm, identify the best route between two nodes of the network In this step, routers choose the best route to every node. They do this using an algorithm, such as the Dijkstra shortest path algorithm. In this algorithm, a router, based on information that has been collected from other routers, builds a graph of the network. This graph shows the location of routers in the network and their links to each other. Every link is labeled with a number called the weight or cost. This number is a function of delay time, average traffic, and sometimes simply the number of hops between nodes. For example, if there are two links between a node and a destination, the router chooses the link with the lowest weight. " Distance vector algorithms are discussed at: [ http://computer.howstuffworks.com/routing-algorithm4.htm ] "DV algorithms are also known as Bellman-Ford routing algorithms and Ford-Fulkerson routing algorithms. In these algorithms, every router has a routing table that shows it the best route for any destination. " " Here are some other links that you will likely find useful: Understanding Routing Protocols [ http://www.oreillynet.com/pub/a/network/2001/05/22/net_2nd_lang.html ] Routing 101: Routing Algorithms [ http://www.samspublishing.com/articles/article.asp?p=27267 ] I trust this has answered your question satisfactorily. If you require a clarification, please request one, especially before rating this answer. Thank you for bringing your question to Google Answers! Regards, Andrewxmp
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