Decisions usually based on knowledge of routing

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Unformatted text preview: nd routing decisions usually based on knowledge of routing network (not always) network distributed routing • using local knowledge, info from adjacent nodes, info from all using nodes on a potential route nodes central routing • collect info from all nodes issue of update timing when is network info held by nodes updated fixed - never updated adaptive - regular updates Routing Strategies - Fixed Routing Routing use a single permanent route for each use source to destination pair source determined using a least cost algorithm route is fixed at least until a change in network topology hence cannot respond to traffic changes advantage is simplicity disadvantage is lack of flexibility Fixed Routing Routing Tables Routing Strategies - Flooding Routing packet sent by node to every neighbor eventually multiple copies arrive at destination no network info required each packet is uniquely numbered so duplicates each can be discarded can need some way to limit incessant retransmission nodes can remember packets already forwarded to nodes keep network load in bounds keep or include a hop count in packets Flooding Example Example Properties of Flooding Properties all possible routes are tried very robust at least one packet will have taken at minimum hop count route minimum can be used to set up virtual circuit all nodes are visited useful to distribute information (eg. routing) disadvantage is high tr...
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This note was uploaded on 10/08/2011 for the course INFORMATIO ECOM 4321 taught by Professor Mr.ehab during the Spring '09 term at Islamic University.

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