[e2e] TCP losses

Fred Baker fred at cisco.com
Mon Feb 28 09:41:27 PST 2005

At 10:54 AM 02/28/05 +0100, Sireen Habib Malik wrote:
>How long does TCP take to decide that its connection has gone to the dogs 
>and that the Application must do something about it? RFC1122 (section 
> talks about "atleast" 100seconds. Is this applied practically?

By some, yes, and often not. Practically, a routing outage lasting for tens 
of seconds often results in TCP sessions failing. I'm not sure I would peg 
it to 100 seconds nowadays, but some do seem a little brittle.

>At this point, i am interested in knowing what breaks TCP outside its own 
>congestion related problems.  What are those failures? How frequently they 
>occur? Any idea of duration?

I would call those "loss-related", not "congestion-related". TCP only sees 
congestion in the form of loss or variation in RTT.

>It would be nicer, if the errors relevant for future large bandwidth-delay 
>product IP over DWDM networks be given priority.

I'm not sure I understand that statement. Are you asking responders to 
think about DWDM (because it is interesting to you), or wondering whether 
errors in a DWDM environment should be treated in some special way by TCP, 
or what? 

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