Method for Retransmitting Fragmented Packets
AssigneeThales
InventorsSebastien MARCILLE, Christophe LE MARTRET, Philippe CIBLAT
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Abstract
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.
Claims20
A method for retransmitting fragmented packets between an emitter and a receiver, said fragmented packets being obtained by fragmentation of a data packet to be transmitted, wherein said method comprises at least the following steps, for each fragmented packet:
- assigning a persistence P(i) of transmission to each fragmented packet, so that the sum of the persistences over the set of said fragmented packets arising from a data packet is equal to a predetermined overall cost C of transmitting said data packet and that the persistence P(1) assigned to the first fragmented packet is strictly less than said overall cost C;
- adding an error-detecting code CRC to each 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 remaining P(i)−c(i) to the next fragmented packet:
- 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 strictly less than the persistence P(i), retransmitting said fragmented packet and incrementing said transmission credit counter c(i),
- in the converse case, inferring the failure of the transmission of said fragmented packet.
Dependencies are inferred from the claim text.