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Routing

Routing is the process of forwarding packets from their source machine towards their destination. Things that do this are called Routers and can be either dedicated hardware or a general purpose computer with two (or more) network interfaces.

Static Routing is done on simple networks that do not change much. They have a simple list of where to send traffic that comes their way. This list is called a Routing Table. If the network changes the list must be updated manually by the network administrator.

Dynamic Routing is done on large networks that are constantly changing. In such an environment new links between networks are being added constantly and established links can disappear without warning. Routers in these environments run programs that automatically (ie dynamically) update their Routing Tables.

Routers know where to forward packets because they share information on where machines are using a Routing Protocol. There are many routing protocols, although only a few are widely used.

Routing protocols are often divided into two classes based on whether they are designed for use within a set of networks all run by the same owner (interior routing protocols), or are better for inter-domain routing (exterior routing protocols).

The other common classification is distance-vector protocols, which use a measure of how far it is to the destination to select the best route, or link-state protocols, which can use a more complex measure of the state of the connections.

RIP is a distance-vector protocol. It was the first widely used routing protocol, designed at Xerox PARC, and was first used for the XNS protocol suite. It was ported to IP, and has undergone several revisions. It is now seldom used because it has quite poor performance in larger networks (and most networks now are large.) ;)

OSPF (Open Shortest Path First) is the major non-proprietary interior routing protocol in use for IP networks today. OSPF is a link-state protocol.

External linkRSPF (Radio Shortest Path First)

IS-IS is an interior routing protocol developed by the ISO as part of the OSI networking suite. It supports multi-protocol routing and is also used for IP networks.

BGP is the major exterior routing protocol of the Internet.

There are also some proprietary protocols in wide use: External linkCisco's EIGRP is perhaps the most common.

There are several developing protocols intended for use in wireless and mobile wireless networks.

Finally, a note on pronounciation:


Version 9 (current) modified Tue, 03 Jul 2007 23:12:20 +1000 by Dan
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