What happens to the TCP congestion window when packet loss occurs at slow start stage? -


in tcp, packet loss can detected in 2 ways: timeout , 3 acks (for 1 packet, ie. loss packet).

assume timeout has not been reached yet, happens congestion window if packet loss happens during slow start stage? congestion window still increase 1 when receiving first duplicated ack?

for example, @ view of sender, window size 3: [1 2 3]

packet 1 , ack (the ack packet 1) sent , received. therefore window size increases 1, ie. 4: [2 3 4 5]

packet 2 sent it's lost. when packet 3 sent successfully, duplicated ack (still packet 1) arrives, window size @ point?

1) if window size increase due receiving of first duplicated ack (note sender doesn't know packet loss because there 1 duplicated ack , timeout has not been reached yet), should be: [2 3 4 5 6]

2) otherwise, perhaps because ack packet 1 has been received (because packet 1 sent successfully), window size may remain 4: [2 3 4 5]

which 1 true tcp?

many thanks!

although might off topic @ stackoverflow, still believe important , interesting issue. post answer find here:

a similar (actually same) question: does tcp increase congestion window when dup acks arrive?

answer: https://tools.ietf.org/html/rfc5681#section-3.2

in more detail:

on first , second duplicate acks received @ sender ... tcp sender must not change cwnd reflect these 2 segments

for each additional duplicate ack received (after third), cwnd must incremented smss.


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