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Selective Acknowledgement and Retransmission in a Packet Switched Network

IP.com Disclosure Number: IPCOM000049406D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Brodd, WD: AUTHOR

Abstract

In frame or packet data communication transmission protocols, it is common practice to sequentially number the data packets. The sequence numbers are used for a variety of functions. Among these are the recovery of lost or mutilated packets, the ordering of the data packets, and the measurement of the utilization of the system.

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Selective Acknowledgement and Retransmission in a Packet Switched Network

In frame or packet data communication transmission protocols, it is common practice to sequentially number the data packets. The sequence numbers are used for a variety of functions. Among these are the recovery of lost or mutilated packets, the ordering of the data packets, and the measurement of the utilization of the system.

When a packet is correctly received at the addressed receiving station, the receiver generally acknowledges the correct receipt thereof. How this is accomplished can have a substantial effect on the throughput or efficiency of the system and buffering requirements at the transmitting station, especially so when the system includes a long delay segment such as a satellite link at high transmission speeds. In this regard it should be noted that a lost or mutilated packet is considered lost or mutilated because of a hiatus in the sequence numbers of correctly received packets.

In the described acknowledgment technique the recipient station periodically and/or upon receipt of a non-contiguous sequence number prepares an acknowledgment message which is transmitted to the sending station. The message has the following format: (NS Low), (Resend Count). (NS Hi) where (NS Low) is a number normally set to one greater than a previously acknowledged, correctly received packet number or to a lower number to acknowledge retransmitted frames, (NS Hi) is a number representing a correctly received packet which immediately follows one or more dequentially numbered packets which have been either lost or mutilated in transmission, and (Resend Count) i...