Hi First post and something I have been wrestling with a while-its all around TCP Dup Ack's and Retransmissions.I have watched and read some excellent stuff from Chris Greer, so I have tried to research it :-)
Firstly, can I put down what I think each is-and then be rebuked if necessary:
Retransmissions-Retransmissions are initiated by the sender if there is no response within it's retransmission timer-so it doesn't need to be told by the client/receiver something has been lost-it just resends?
Dup Acks-Dup Acks are sent by the client/receiver back to the sender, telling the sender something is out of order
Here's my problem-I have a trace where I can see loads of Dup Ack's (sometime 300-400-but only 2 retransmissions-10 second trace over a high speed cable link). RTT says consistent at about 22ms (there are a few spikes to 90s but I cant see any Dup Acks or Retranmissions at the same time?) So Dup Ack's indicate packet loss? But again, the throughput trace looks clean, as does the window scaling.
Should I be worried by these Dup Acks? As all other indications look ok (I think!)
Thanks
cabs
