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Lectures notes for 2010 - KTH

Lectures notes for 2010 - KTH

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Routing<br />

The internet protocols are based on moving packets from a source to a destination<br />

with each hop making a routing decision.<br />

Two components to routing:<br />

• packet <strong>for</strong>warding - Routing Mechanism: search the routing table and decide<br />

which interface to send a packet out.<br />

• A matching host address? If no,<br />

• A matching network address? (using longest match) If no,<br />

• Default entry.<br />

• computing routes - Routing Policy: rules that decide which routes should be<br />

added into the routing table.<br />

Traditionally most of the complexity was in the later (i.e., computing routes) while<br />

packet <strong>for</strong>warding was very straight <strong>for</strong>ward -- this is no longer true due to QoS.<br />

Routers vs. hosts -- a node can be both<br />

• Routers <strong>for</strong>ward IP packets<br />

• Hosts generate or sink IP packets<br />

Maguire Routing 2: 4 of 52<br />

maguire@kth.se <strong>2010</strong>.03.21 Internetworking/Internetteknik

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