Re: [conex] Expiration of credits

[John Leslie <[e-mail]>]

Mirja Kuehlewind <[e-mail]> wrote:
> 
> I guess a cap is even more complicated. An expiration would somehow
> depend on RTT but the num of credit you want to send (at once)
> depend on the congestion control mechanism in the endsystem.

   IMHO you should never depend upon a credit lasting more than one
RTT.

   That said, credits are intended for start-up -- and in many cases
currently, you will need more than one RTT to infer that a packet
was dropped (because ECN marking wasn't enabled at the bottleneck).
There may be cases where you should decide whether to issue additional
credits while waiting for a timeout -- and there are certainly cases
where you _don't_ want to issue such additional credits.

> If I increase the cwnd by 100 packet in one RTT I might want to
> send 100 credits

   I cannot imagine such a case. Credits need never exceed the greatest
plausible loss. I cannot imagine increasing cwnd by 100 when I expect
100% packet loss.

   IMHO, credits are not generally appropriate for any situation where
you are increasing cwnd -- but I'm sure _someone_ will find a case
where it would help... :^}

--
John Leslie <[e-mail]>