Thanks! What you've described is the process of handshakes or the real data-sendings bw. PC1 and PC2? How could R1/R2/R3 decide to route if no handshakes have taken place and if hand shakes are already done, why do R1/R2/R3 still need to check and decide what the next hop is? BTW, did you say routers send packets? Why not frames or segments/datagrams?