[e2e] Are Packet Trains / Packet Bursts a Problem in TCP?

[Lloyd Wood]

At Tuesday 26/09/2006 13:29 -0400, Craig Partridge wrote:

>In message <8f884bb031b3678c4b56874456ec25aa at mac.com>, rick jones writes:
>
> >Maybe I'm trying to pick a nit, but was the underlying problem that it
> >was bursty in the initial transmission, or was the underlying problem
> >really that it continued to retransmit the bursts, without any (IIRC)
> >exponential backoff?
>
>Hi Rick:
>
>Excellent question, on which my memory is imperfect.  Here's my best
>recollection.
>
>Pre-1988 BSD TCP (and, indeed, I believe all TCPs) would start by sending
>as close to an entire window's worth of traffic as they could (e.g. as fast
>as the application could stuff the transmission queue, data got sent up
>to the window size).
>
>In case of loss, TCP retransmitted only the missing segments,

why did we ever bother with SACK, then?

thanks,

L.


>but as soon as all
>losses were recovered from, TCP resumed hammering full bursts.  So TCP was
>not go-back-N, but had a sort of strange burstiness of the form:
>
>     initial burst -- causing loss -- followed by recovery -- followed by
>     new burst
>
>Others who were there, please correct, update as appropriate.
>
>Thanks!
>
>Craig