Method for retransmitting fragmented packets

摘要

A method is provided for retransmitting fragmented packets for which a transference of retransmission credit is performed from one fragment onto the next. The method makes it possible to do away with the drawbacks of the methods existing by appreciably improving performance in terms of untransmitted packet rate and by making it possible to configure the distribution of the error probabilities for the fragments of an IP packet.

主权项

1. A method for retransmitting fragmented packets between an emitter and a receiver, said fragmented packets being obtained by a fragmentation of a data packet to be transmitted, wherein for each said fragmented packet said method comprises:
assigning a persistence P(i) of transmission to each fragmented packet, so that a sum of the persistences assigned to said fragmented packets is equal to a predetermined overall cost C of transmitting said data packet and that the persistence P(1) assigned to a first fragmented packet, among said fragmented packets, is less than said overall cost C; adding an error-detecting code CRC to each said fragmented packet; incrementing a transmission credit counter c(i), initialized beforehand to 0, and transmitting said fragmented packet to the receiver; on receipt of a positive acknowledgement of receipt of said fragmented packet, transferring the transmission credit counter remaining P(i)−c(i) to a next fragmented packet using a relationship:
P(i+1)=P(i+1)+P(i)−c(i); on receipt of a negative acknowledgement of non-receipt of said fragmented packet or if no acknowledgement is received after a predetermined time span: if the transmission credit counter c(i) is less than the persistence P(i), retransmitting said fragmented packet and incrementing said transmission credit counter c(i), if the transmission credit counter c(i) is not less than the persistence P(i), inferring a failure of a transmission of said fragmented packet.