Features of go back N Window size= n Sender cannot send packet i+N until it has received the ACK for packet i Receiver operates just like in Stop and Wait Receive packets in order Receiver cannot accept packet out of sequence Send RN=i+ 1=> ACK for all packets up to and including i Use of piggybacking When traffic is bi-directional RN's are piggybacked on packets going in the other direction Each packet contains a SN field indicating that packet's sequence number and a RN field acknowledging packets in the other direction <--Frame header -------> SN RN Packet CRCFeatures of Go Back N • Window size = N – Sender cannot send packet i+N until it has received the ACK for packet i • Receiver operates just like in Stop and Wait – Receive packets in order – Receiver cannot accept packet out of sequence – Send RN = i + 1 => ACK for all packets up to and including i • Use of piggybacking – When traffic is bi-directional RN’s are piggybacked on packets going in the other direction Each packet contains a SN field indicating that packet’s sequence number and a RN field acknowledging packets in the other direction <--Frame Header ---------> SN RN Packet CRC