how to determine value of alpha for retransmission timer of tcp

Question

i have sniffed a file upload to find out tcp segments. i see a dup ack and and fast retransmission in the ethereal output. i want to verify that the timer for retransmission of this packet is indeed the one that is indicated by jacobson's formula. i have the timestamps for all segments. what portion of my linux source should i study to find out the retransmission timer value calculation algorithm used by my system. if it is the same as jacobson's algorithm i want to know the value of alpha for the retransmission timer.

Answer 1

There is a lot of congestion implementations right now in the linux kernel, and the default one changes at least twice in 2.6.x branch. You should firstly find out which algorithm you are using and afterwards read some documentation on it. (hint: )

You can also take a look to the Congestion control advancements in linux. This second article gives you some hints about all available congestion algorithms too.

As congestion is one of the biggest problems on networks, there is a lot of studies, reports, etc available on the Internet. You can check out too the linux kernel development lists/news groups as there are a lot of discussion on it too.