[e2e] cwnd update correction for congestion avoidance

[Mark Allman]

> I'm now taking this to tcpm, too...
> 
> On tuesday, Anil Agarwal sent a message to the end2end list
> which made it clear that the equation:
> 
> cwnd += SMSS*SMSS/cwnd
> 
> from 2581 does not really add a segment every RTT as desired.
> (He also went into some ABC related details, but I'll
> not go into them for now to keep things simple.)

A note here is that the above is not the only way the spec allows for
cwnd growth during congestion avoidance.  Byte counting is also
explicitly allowed by RFC 2581:

   Another acceptable way to increase cwnd during congestion avoidance
   is to count the number of bytes that have been acknowledged by ACKs
   for new data.  (A drawback of this implementation is that it requires
   maintaining an additional state variable.)  When the number of bytes
   acknowledged reaches cwnd, then cwnd can be incremented by up to SMSS
   bytes.  Note that during congestion avoidance, cwnd MUST NOT be
   increased by more than the larger of either 1 full-sized segment per
   RTT, or the value computed using equation 2.

allman


--
Mark Allman -- ICIR -- http://www.icir.org/mallman/



-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 185 bytes
Desc: not available
Url : http://www.postel.org/pipermail/end2end-interest/attachments/20050201/256299d5/attachment.bin