CSC458H1 Lecture 4: FORWARDING-ROUTING
Document Summary
Forwarding: hop-by-hop packet forwarding, each router has forwarding table = maps destination ip, steps of the router to handle forwarding address to outgoing interface. Lookup packet destination ip address in header forwarding table. Unknown drop packet; send icmp destination unreachable back to the packet sender. Forward the packet to the outgoing interface transmit packet onto the link. Repeat until packet reaches destination: ingress input lines to router; egress output lines from router, address lookup strategies, enteries per address forwarding table has entry per ip address. Match destination address of incoming packet to forwarding-table entry to find outgoing interface. Problem: large tables many entries = require a lot of memory. Slow lookup, and keeping table updated is tedious: entry per address class forward table has entry per class-based prefix. Disregard host id, match only the network id. Unless host is directly connected to this router destination. Ip address has same network id as the router.
