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Re: "Binary XML" proposals
- From: "Stephen D. Williams" <email@example.com>
- To: "Al B. Snell" <firstname.lastname@example.org>
- Date: Fri, 13 Apr 2001 11:04:10 -0400
"Al B. Snell" wrote:
> On Fri, 13 Apr 2001, Stephen D. Williams wrote:
> > No, the difference is that after connection, the rest of the
> > session/conversation can be handled by another thread/process/cpu with
> > TCP. You can't do that with UDP since there is no way to know at the
> > kernel/driver level what logical process an incoming UDP packet is bound
> > for.
> Oh, you mean once conversations have started and you want to maintain
> state? Well, either keep the table of
> which-process-handled-which-conversation in the master process, or use the
> master process purely as a broker which replies (on conversation
> setup) with a destination port to use that points to the correct child. In
> practice, though, if you actually want a stateful conversation like that,
> straight UDP probably *isn't* for you!
You Can dynamically assign a UDP port that the rest of the conversation
can proceed on in a separate thread, but that limits you to 64K
concurrent conversations. TCP has no such limit; it can have 64K
conversations with Each remote IP address.
Presense/IM (i.e. Buddylist/AIM/ICQ/Jabber) is a good model where it has
been generally agreed that a long-lived TCP connection is needed. The
communication model is the first widely used (as in number of actual
end-user/computers) instance of async message oriented routing. In my
mind, as I've espoused for a long time, it's a great potential platform
for other applications shipping generic XML and more. It is in fact a
good example of the savings that message pipelining can buy you.
> I'd like RDP resurrected. It strikes me that RDP can be implemented in
> userland on top of UDP (which is, at heart, a controlled gateway to IP
> itself)... that might be worth examining.
> Alaric B. Snell
> http://www.alaric-snell.com/ http://RFC.net/ http://www.warhead.org.uk/
> Any sufficiently advanced technology can be emulated in software
Stephen D. Williams
43392 Wayside Cir,Ashburn,VA 20147-4622 703-724-0118W 703-995-0407Fax