TCP Retransmission

sir_creamy_

Why does a TCP sender need to receive 3 duplicate ACKs for the same data before it decides that the segment prior has been lost? Does anyone know why "3" is the magic number?

seuss_ssues

http://www.youtube.com/watch?v=yPzAjiLr5Zw

sorry, i couldnt help myself.

To answer your question. I do not know.

Possibly 3 is a relatively low number. It is enough to cause a pause to allow the data to be recieved properly, but not long enough to cause a noticeble disturbance in the communication channel.

JDMurray

This might be a timing factor based on the connection's Maximum Segment Lifetime (MSL) and not a hard-coded retry value. Three ACKs may be all that there's time to send before the MSL expires. What is your stack's MSL and how long does it takes to receive the last ACK?

RFC 793 - Transmission Control Protocol