TCP Session -- Path selection

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Apr 17th, 2002
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After establishment of TCP session, whether the following data packets traverse same routing path ( to & fro) which path used for establishment of session?

I am having two providers A & B. Assume TCP session is established through A with a remote server and immediately the link from A is down, then reestablishment of session should take place through B or else the following data packets can come through B?

Thanks in advance...



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Gilles Dufour Wed, 04/17/2002 - 10:47
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TCP session should not be reset.

TCP data should flow through B with no problem.

Unless there is 2 NAT devices (1 for ISP A and 1 for ISP B). Therefore the NAT session will need to be re-established forcing the TCP session to be reset.

ashok_boin Wed, 04/17/2002 - 12:12
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So you meant to say that there is nothing like same path should be used for the following data packets after establishing the session. I said it corrrect, correct me if wrong?



michaeljmorris Wed, 04/17/2002 - 13:23
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can you explain this better ? The TCP session is Layer4 and will travel whatever path Layer 3 (IP) can find that works. If the A route goes down as long as the routers can reconverge and find the B route the session will continue to work (minus a short delay for the routing protocol reconvergence).


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