[Kamailio-Users] re-invite mid call?

[Alex Balashov]

On 01/01/2010 11:32 AM, Antonio Goméz Soto wrote:

> I am sorry, maybe I do not understand enough about SIP and proxies.
> Wouldn't it be possible to fake re-invites? Tell each phone that it
> gets a reinvite coming from the other phone, and basically redirecting
> the sound stream to an rtpproxy for example? or a codec translator?
>
> I'd like to switch from g711 to g729 when the link gets overloaded
> for example. Or record the phonecall.
>
> I am trying to learn more about SIP. Aren't reinvites within
> a dialog common?
>
> Maybe I could make changes to openser to enable this?

Yes, reinvites are common, and you have correctly ascertained their 
purpose.

What I think you are not understanding is that a reinvite, like any 
other request, must be originated from an endpoint (a user agent).  A 
proxy is not a user agent;  it cannot generate replies.  The only 
thing proxies do, as a matter of definition, is forward requests they 
receive, and forward replies to them in the opposite direction (when 
applicable).

Again, I draw your attention to the HTTP server vs. Squid analogy we 
made earlier.  The question you are asking sounds equivalent to, "Can 
Squid send a GET request?"  The answer is no, Squid cannot send any 
requests;  it can only act on requests it receives and direct them 
somewhere.


-- 
Alex Balashov - Principal
Evariste Systems
Web     : http://www.evaristesys.com/
Tel     : (+1) (678) 954-0670
Direct  : (+1) (678) 954-0671