Go Back N ARQ (Sliding Window) Stop and Wait is inefficient when propagation delay is larger than the packet transmission time Can only send one packet per round-trip time Go Back n allows the transmission of new packets before earlier ones are acknowledged Go back n uses a window mechanism where the sender can send packets that are within a"window(range)of packets The window advances as acknowledgements for earlier packets are received WINDOW WINDOW WINDOW WINDOW PKT-o PKT-2 PKT-3 PKT-4 PKT-5PKT-6 PKT-7 PKT- PKT-9 入 AcK-olAcK-1 ACK-2 ACK-3 ACK-4ACK-5lACK-6 ACK-7AcK-8IGo Back N ARQ (Sliding Window) • Stop and Wait is inefficient when propagation delay is larger than the packet transmission time – Can only send one packet per round-trip time • Go Back N allows the transmission of new packets before earlier ones are acknowledged • Go back N uses a window mechanism where the sender can send packets that are within a “window” (range) of packets – The window advances as acknowledgements for earlier packets are received PKT-0 PKT-1 PKT-2 PKT-3 PKT-4 PKT-5 PKT-6 PKT-7 PKT-8 PKT-9 ACK-0 ACK-1 ACK-2 ACK-3 ACK-4 ACK-5 ACK-6 ACK-7 ACK-8 WINDOW WINDOW WINDOW WINDOW