[JDEV] Videoconferencing with jabber / Re: [speex-dev]Videoconferencing with speex and jabber

Carsten Breuer CarstenBreuerJabber at openwin.de
Thu Nov 27 16:59:54 CST 2003

Hi Matthias,

>>they can split the internet from the internal net. Have you ever tried 
>>to get Netmeeting running over a linux gateway running on a 486DX4100 
>>without the need to switch of your firewall. It is completly a mess.
> Yes I have ... that what H.323 Gatekeepers are for.
> Do you think the ITU has choosen UDP as a transport for the media data
> if they wouldn't have had a good reason? TCP has many disadvantages for
> for real time data because of the build in error recovery and flow
> control. TCP is just not made for real time data.

Sure, i agree with you. That was not my point if you use TCP or UDP.
I think also that UDP is the right choice for that stuff.
The point is that after a call is made, the oposite client can
connect to any port, so it must be open. This is also if you are
running a gatekeeper (www.openh323.org).

> And UDP/TCP is the point. You need the Gatekeeper for H.323 and the
> proxy for SIP not because they don't have external servers (in fact they
> can have), but because it's often hard to cross NAT with UDP packets as
> there is no connection for which the NAT router can know how do deliver
> incoming IP packets.

Yes, that could be true. My point of interest on gatekeepers is the 
level of DSL-Rourters or smal linux boxes running some IP-Masqurading

> There are not much techniques available to solve this problem (beside
> the Gatekeeper/Proxy on the NAT system). Possibilities include:
> - using TCP - problems see above. Sometimes it's implemented that the
>   TCP connection is dropped as soon as there should be incoming traffic
> - Using any sort of a proxy on the NAT: Gatekeepers, proxies, SOCKS, ...

OK, but what is the situation if both clients are connected via a ISP.
The dont have nothing tu do with NAT etc. What's the situation then.
What is if one has a DSL-Router with a VPN behind (192.168) and the 
other partner have a direct conection (ISP)?



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