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