Is it necessary… routing?
Is routing necessary for person A?
Yes, in packet switched network, it is necessary to show person A what route to follow at each node (router), in the network. Home and office networks are different and far away from each other: we need some kind of inter-networking to allow them communicate. When A reaches router R_A, it brings information about B, this information should be sufficient to move A to the next step (router). In our example we’re presented by 4 choices to reach R2. At R2, A present the same information about B to router R2. Because the routing decision is consistent in the this network, R2 would froward A towards R_B.
No, routing is not necessary if we use LL leased line: modem, v.24, 35 or X.21 interface type to connect person A to B. Other switched circuits technologies such as: Frame Relay (FR), X.21, ATM, P1024B or C, would serve the same purpose. More advanced technologies would help also avoid routing: tunnel, vpn, vrf, xconnect, vpls, pseudo wire, mp-bgp, mpls labelling, etc. In this cas, we’re sur that the “tunnel” will conduct A directly to R_B; there’s no other possible choice or chance of a routing mistake…
