Bootstraping forwarding tables 16 a Whenever an interface is initialized a direct route(to a host in a point-to-point link or to a network in a Lan) is automatically created a With iP address and subnet mask configured n For nonconnected networks, n Hosts to find default routers Configure manually through route command Use ICMP router discovery protocol Use ICMP redirect ■ Use dhcp Routers run a routing protocol (a routing daemon) to automatically discover routes
Bootstraping forwarding tables 16 Whenever an interface is initialized, a direct route (to a host in a point-to-point link or to a network in a LAN) is automatically created. With IP address and subnet mask configured For nonconnected networks, Hosts to find default routers: ◼ Configure manually through route command. ◼ Use ICMP router discovery protocol ◼ Use ICMP redirect ◼ Use DHCP Routers run a routing protocol (a routing daemon) to automatically discover routes
Characteristics of IP forwarding 17 a Both hosts and routers are involved in forwarding. Compared with routers, a host makes a much simpler binary decision. o IP forwarding is done on a hop-by-hop basis. n It is assumed that the next-hop router is really closer to the destination o IP forwarding is able to specify a route to a network and not have to specify a route to every host
Characteristics of IP forwarding 17 Both hosts and routers are involved in forwarding. Compared with routers, a host makes a much simpler binary decision. IP forwarding is done on a hop-by-hop basis. It is assumed that the next-hop router is really closer to the destination. IP forwarding is able to specify a route to a network, and not have to specify a route to every host
Forwarding for different types of routing 18 a Unicast routing a Longest prefix matching on the IP destination addresses a Unicast routing with TOs a longest prefix matching on the ip destination addresses t exact match on tos 口 Multicast roUting a Longest prefix matching on the ip source address exact match on source address, destination address and incoming interface
Forwarding for different types of routing 18 Unicast routing Longest prefix matching on the IP destination addresses Unicast routing with TOS Longest prefix matching on the IP destination addresses + exact match on TOS Multicast routing Longest prefix matching on the IP source address + exact match on source address, destination address, and incoming interface
Routing functionalities vs forwarding algorithms n Different functionalities require different forwarding algorithms routing Unicast Unicast Multicast functionrouting routing with routing TOS Forwarding Longest Longest prefix Longest prefix algorithm prefix matching on the matching on the matching IP destination IP source address on the ip addresses exact match on destination exact match on source address addresses TOS
Routing functionalities vs forwarding algorithms 19 Different functionalities require different forwarding algorithms Routing function Forwarding algorithm Unicast routing Unicast routing with TOS Multicast routing Longest prefix matching on the IP destination addresses Longest prefix matching on the IP destination addresses + exact match on TOS Longest prefix matching on the IP source address + exact match on source address, …