[Serusers] rtpproxy question

[Klaus Darilion]

But if UA1 ist not behind NAT, proxy 2 should activated its rtpproxy to
enable a communciation although there are more than 2 Via headers.

I guess there is no solution yet which will work in all scenarios as one
SIP proxy will never know the NAT-traversal strategy of other proxies.

regards,
klaus

> -----Original Message-----
> From: Maxim Sobolev [mailto:sobomax at portaone.com] 
> Sent: Monday, November 03, 2003 6:40 PM
> To: Jan Janak
> Cc: Klaus Darilion; serusers at lists.iptel.org
> Subject: Re: [Serusers] rtpproxy question
> 
> 
> There is another possible solution: modify nathelper to only 
> apply RTP 
> proxy redirection if there is only one Via in the request. This will 
> ensure that in the situation when there are multiple SIP/RTP 
> proxies in 
> the path only first one will handle RTP. Unfortunately it 
> will not help 
> if there are any SIP B2BUAs on the way.
> 
> -Maxim
> 
> Jan Janak wrote:
> > On 03-11 19:18, Maxim Sobolev wrote:
> > 
> >>Klaus Darilion wrote:
> >>
> >>
> >>>Hi!
> >>>
> >>>As the RTP relaying does not work with 2 RTP proxies, how 
> can a proxy 
> >>>detect
> >>>if the RTP stream is already redirected to an RTP proxy?
> >>>
> >>>My problem is the following scenario:
> >>>
> >>>UA1   --NAT--   SIP proxy 1   --   SIP proxy 2   --NAT--   UA2
> >>>               rtpproxy1          rtpproxy2
> >>>
> >>>UA1 invites UA2. SIP proxy 1 detects that UA1 is behind 
> NAT and enables the
> >>>rtpproxy1 and forwards the invite to SIP proxy2. SIP proxy 
> 2 knows that UA2
> >>>is also behind NAT. Usually, SIP proxy 2 would activate 
> the rtpproxy2, but
> >>>in this case this would not work as there is already an 
> rtpproxy involved.
> >>>How can the SIP proxy 2 detect that the IP address in the 
> SDP is the IP
> >>>address of an RTP proxy?
> >>>
> >>>
> >>
> >>Known problem. I think that I'll modify nathelper, so that 
> >>force_rtp_proxy() will insert some flag into the SDP body, 
> which will 
> >>tell other proxies along the request route that there is no 
> need to put 
> >>another RTP relay into the RTP path.
> > 
> > 
> >   Another option would be to insert a header field telling 
> that another
> >   RTP proxy is being used already.
> > 
> >   The problem is that both solutions (header field and SDP 
> flags) will
> >   be not interoperable.
> > 
> >   Another option would be to modify the RTP proxy so that it will be
> >   symmetric only for user agents that belong to the domain 
> of the proxy.
> >   That would probably complicate things a bit.
> > 
> >     Jan.
> > 
> > 
> 
> 
>