[e2e] 10% packet loss stops TCP flow

Sireen Habib Malik s.malik at tuhh.de
Mon Feb 28 03:22:44 PST 2005


Assume X is the time the TCP is allowed to wait to recover from the 
fault (RFC1122, TCP Connection Failures, atleast 100seconds).

During this time X, if  Pp does not improve then Pc approaches 0 with T 
going higher. It does give the impression that connection has no chance 
to recover and finish.

However, if in X time ACKS come (basically Pp improved as fault is 
removed) TCP will recover and finish the transmission "some day"!! Seems 
then Pc=100%!

I think the more interesting case is that what is the probability that 
TCP will tell the application to kill the connection in time X,  if Pp 
is the loss probability, etc.....? 



Noel Chiappa wrote:

>    > From: Jonathan Stone <jonathan at dsg.stanford.edu>
>    >> T retransmissions .. given that it has N total segments to transmit,
>    >> .. Pc = f(Pp, T, N), where Pc is the probability of the successful
>    >> completion of the tranmssion, and Pp is the probability of the loss of
>    >> any individual packet.
>    > Are you deliberately tempting your readers to fall into the fallacy of
>    > assuming packet loss is statistically independent, and thus of assuming
>    > Poisson behaviour of packets in the Internet?
>Well, it depends on what's causing the packet loss, doesn't it? E.g. if it's
>congestion, yes there is a chance it will be non-random (although it will
>depend on what drop algorithm the switches/routers are using). However, if
>it's a lossy radio link, it might be fairly well random.
>May I also note that Pc calculated by the simplistic formula I point toward is
>actually something of an *upper* bound, and any deviation away from perfect
>randomness in packet dropping will *reduce* it. (If the losses are not evenly
>randomly distributed, then the probability of the loss of the T retransmission
>of a given packet needed to kill the connection is even *higher* than the Pp^T
>you get with a random model, no?)
>	Noel


Sireen Malik, M.Sc.
PhD. Candidate,

Communication Networks
Hamburg University of  Technology,
FSP 4-06 (room 3008)
Denickestr. 17
21073 Hamburg, Deutschland

Tel: +49 (40) 42-878-3387
Fax: +49 (40) 42-878-2941
E-Mail: s.malik at tuhh.de

--Everything should be as simple as possible, but no simpler (Albert Einstein)

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