[Serusers] rtpproxy question

[Maxim Sobolev]

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.
> 
>