[OpenSIPS-Users] detecting mediaproxy across multiple opensips instances

Dan Pascu dan at ag-projects.com
Tue Jun 9 10:39:08 CEST 2009

On 9 Jun 2009, at 02:53, Jeff Pyle wrote:

> Hello,
> We'll be facing a scenario soon where a SIP call will traverse at  
> least two
> Opensips proxies.  Depending on the conditions at the time, either  
> proxy
> could conceivably use an engage_media_proxy().  The circumstances  
> are few
> that would cause both to do it, but the possibility still exists.
> Is there a way the second Opensips proxy can detect the fact the  
> first one
> has already engaged the mediaproxy?

You could add a SIP header and not start mediaproxy if present. Or use  
some heuristics on the IP addresses from the SDP (origin IP vs c= line  
IP). Or depending on your topology, you can know that a certain proxy  
has a special relationship with the caller/callee and it's the only  
one that should call engage_media_proxy()

> Is it relevant that both Opensips' dispatchers in this case will be  
> talking
> to the same relay?  This is the case.

No. It works without any issues.

> What are the implications if both proxies are permitted to
> engage_media_proxy()?

None. You can chain as many media relays as you want. You can call  
engage_media_proxy() and every proxy in the path if you want, it will  
make no difference other that having the traffic routed trough  
multiple media relays in your network (or not if you only use one  
relay). The only required thing is that they have a public IP so they  
don't deadlock when chained.


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