[JDEV] UDP vs TCP

[mark at mjwilcox.com]

On 2 Sep 00, at 9:19, Thomas Charron wrote:

> > >Finally, the last four companies I've worked at (read: EVERY company I've
> > >worked at which had a computer) has had my computer situated behind a
> proxy.
> > >Most Universities now use proxies for all their computers (I know
> University
> > >of Florida even proxies the residence halls.) And I have a NAT proxy at
> > >home, so that my notebook can access the internet through my linux
> 'server'.
> > >How do these computers connect, if at all, on a UDP system?
> > UDP sits behind a NAT proxy in same method TCP does :P. Actually thats how
> > a lot of UDP applications work (mostly games) behind Proxies :P
> 
>   WHOAH there Nellie.  That will only work if you NAT *ALL* incoming UDB to
> your internal network, which, well, it's a bad idea needless to say.  In the
> case of TCP, the connection is initiated from inside machine, and a logical
> session is created.  UDP, on the other hand, has no logical connection to
> NAT.  In order to do UDP over NAT< you quite literally have to select, port
> by port, what UDP packets will be forwarded to what internal machine.  A UDP
> based system *CANNOT* function the same way behind a NAT firewall, or any
> other sort of firewall, for that matter..

Bingo. This is one reason why RTSP (the streaming protocol) has 
an option to be delivered over HTTP so that it can get through 
firewalls. It's innefficient as hell, but if it works.....

Mark
> 
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Mark Wilcox
mark at mjwilcox.com
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