Re: [Ekiga-list] no video: is video transferred on separate connection?

[Zhang Weiwu <zhangweiwu realss com>]

On 2010年06月24日 03:30, Eugen Dedu wrote:

There are separate ports for video, audio and sip, to my knowledge. http://wiki.ekiga.org/index.php/Understanding_NAT/firewall_issues_with_SIP_clients_%28eg_ekiga%29 has valuable information.

The page contain a lot of useful information, but still reads confusing to me.
Quote from the wiki page:

• what ports are used (RTP audio/video, SIP etc.):

RTP AUDIO stream is usually 5061/5062 (the first port is the steam itself, the second is for statistics; only the first one really matter. Maybe the second one does improve quality under some circumstances)

RTP VIDEO stream is usually 5063/5064 (same as for audio)

This is rather unclear to me. For example, for video "5063/5064" have 4 different meaning to me:

1. does it mean the receiver will use port 5064 and sender using 5063? Like in ftp and nfs protocol, the port of both ends of the connection is restricted to certain ports.
2. does it mean it works either 5063 or 5064 is open for listening on firewall setting?
3. does it mean it works if both of 5063 and 5064 are open for listening on firewall setting?
4. does it mean the connection establishing end of ekiga will try connect to 5063, and failing that, try to connect to 5064? And the connection receiving end of ekiga will listen on both?

More confusing is it did not say who connects to whom. Suppose the quoted wiki means 5063 is a listening port for video, then should the caller connect to callee's port 5063, or should the video sender connect to the video receiver's port 5063? They are not the same thing! For example in my case I am being called by my colleague but I have camera, he doesn't, so I am callee and video sender, it raises the question should I listen on 5063 or him. For me to receive phone call and send video to caller, whose NAT/firewall setting should I touch? It might be basic knowledge to some but really confusing to people who just want to use it.

P.S. this is about the 5th time I try to use ekiga. I try it about once a year since 2005 with that year's latest version, and never managed to make it work on anything beyond text message, neither audio nor video. Despite trying in multiple different networks, I am usually reported my NAT is symmetric. Since the article says most NAT are not symmetric, I must assume there is something wrong in China, since we have too much particularity here. I guess it's a bit too complicated to me. Even though being computer science graduate I never understood how this thing work (yes, I had many understandings, but each conflict with practical observation), but still trying very hard to figure out how to use it. Or, is it easier to fall back to old H.232? I remember I used to use video stuff without knowing how it worked in campus back in 2003, on NetMeeting that came default with Windows 2000, but I could not recall if there was NAT firewall by that time thus not sure what really bring so much trouble, NAT or new protocol.