Thomas Kunz
Systems and Computer Engineering
360
Detecting Packet Loss Using
Retransmission Timeout (RTO)
nAt any time, TCP sender sets retransmission timer for only one packet
nIf acknowledgement for the timed packet is not received before timer goes off, the packet is assumed to be lost
nRTO dynamically calculated
–Connection may be between two machines on same LAN (want low RTO value) or two machines on opposite sides of Atlantic (need higher RTO value)
–Network connection between two machines introduces predictable and constant delay per packet (can use tighter bound) or highly variable packet delay (use less tight bound to avoid unnecessary retransmissions)
–Use observed time difference between packet sent and acknowledgment received to estimate RTO