[OpenSIPS-Users] Mediaproxy ver 2.3.4 - Conntrack meets Music on Hold

[Stuart Marsden]

Hi,

The problem we have, is the implementation of MoH to Invite the MoH 
server and pass the SDP of an existing call is fixed in the 
implementation of the SPA 94X phone - we can't change that.
In fact at the moment we struggle to get Linksys to fix bugs in the 
Phones, never mind change the way they work

Stuart

Dan Pascu wrote:
>
> On 30 Jun 2009, at 19:11, Ruud Klaver wrote:
>
>>> 3) detect this special case and change existing conntrack to point to
>>> the MoH sever, putting it back later
>>
>> We actually considered implementing this, but not for this particular
>> scenario. Some modems seem to switch IP address every X hours. If this
>> change is during a relayed call, the RTP from one end will suddenly
>> come from a new IP address, like in your scenario. What could be done
>> is that the relay keeps listening on the allocated ports in userspace
>> for traffic from a different host and switch the conntrack rule to the
>> new IP if there is no traffic coming in anymore from the old IP.
>
> This will not work in this case. The case you mention was possible 
> because the media relay could detect if the stream coming from the new 
> IP:port was actually the same stream by looking to the serial number 
> present in the RTP. Since that was the same, it could assume that it's 
> the same sender that just happened to have his IP changed during the 
> call. In Stuart's case, since it's a new SIP dialog, with a new RTP 
> stream sent by a different device it will have a different serial 
> number. The only way to work would be to accept any stream which is 
> opening Pandora's box for official media hijacking.
>
> -- 
> Dan
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