[e2e] TCP Framing
vjs at calcite.rhyolite.com
Fri Mar 23 17:40:05 PST 2001
> From: Jonathan Stone <jonathan at DSG.Stanford.EDU>
> >In other words, contrary to various claims, no black magic was required
> >to "page flip" on both input and output more than 10 years ago.
> Yes, provided that the MSS is a multiple of the pagesize, (or the
> sender rounded down to that), and that you already DMAed the packet
> into memory, aligned such that the TCP (or whatever) payload
> ended up page-aligned.
> That is, it works provided the receiver's guess about alignment and
> preceding header sizes pays off...
The proposal also doesn't work unless it's somewhat similar guesses
pay off. That the guesses are made explicit and put on the wire
doesn't change that problem.
I prefer things that just work by default to things that are explicit
but work just as (in)frequently. But that's largely a matter of style.
I'm not a fan of having an on-the-wire protocol for every cloud on
a white board. Many people disagree with me, as demonstrated by
enthusiasm for such as the PPP BOD protocol which can do and does
nothing except put on the wire what both peers either already know or
don't care about.
Vernon Schryver vjs at rhyolite.com
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