40 lines
924 B
Markdown
40 lines
924 B
Markdown
# lec18
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## Heirarchical Routing
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So far we've looked at routing from a very simple point of view.
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To better model reality we'll assume a new constraint: that being the internet as a network of networks.
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This means that the actual routers within each network must maintain multiple forwarding tables.
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One for intra-net routing, and another for inter-net routing.
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## Intra-AS Routing
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### RIP
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Popular because it was included with BSD/unix back in 82.
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Uses simple distance vectoralgoritm for evaluating cost.
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1. Maximum distance of 15 hops
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2. Distance vectors exchanged every 30 seconds
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### OSPF
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> Open Shortest Path First
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Uses a link state algorithm.
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* LS pcket dissemination
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* Topology map at each node
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Security is built into the protocol itself.
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We allow for multiple _same-cost paths_
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Also uni- multi-casting
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## Inter-AS Routing
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### BGP
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> Border Gateway Protocol
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* Allows subnet to advertise its existent
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