Re: PPP is slow (and so is TCP!) [with fixes]
Alan Cox (alan@cymru.net)
Fri, 12 Apr 1996 16:02:56 +0100 (BST)
> send not send the next character until it gets the ack for the
> previous one. Since ACKs are delayed this really slows down
> the arrival of the response to interactively typed characters.
> Second, after I fixed the above problem I found that delayed ACKs
> where not being dealt with correctly. In particular we're
> violating RFC1122 in a couple of places:
>
> o It is required that an ACK packet that is delayed be delayed
> by no more than 0.5 seconds. The implementation can be forced
> to violate this easily. The problem is that every time new data
> arrives we reset the timeout for the ACK. An ACK can get delayed
> for as long as we continue to received data packets in order.
Sounds like we have/had another serious oversight too. BSD doesnt delay
acks on frames that are not mss sized (to avoid tripping nagle). We ought
to be doing the same. I hadnt realised the changes that got put in didnt do
that