[sr-dev] why new tcp connection?

[Iñaki Baz Castillo]

El Sábado, 7 de Noviembre de 2009, Juha Heinanen escribió:
>  > Of course this param just exist in case of a NATted client so dealing
>  > manually with it means:
> 
> why only nated?  this whole thread started as why two tcp connections
> are needed to an ua.  so the parameter would also be added when request
> arrives from non-nated tcp ua so that future requests on this dialog
> back to ua could be made to use the existing tcp connection.

Ok, but for non natted TCP dialogs the usage of "alias" (supported by SR) is a 
working (and really standarized) solution.


>  > I would prefer a new nathelper exported function:
>  >
>  > "nat_check_received()"
>  >
>  > If ";received" param exists it set $du and returns 1.
>  > If not, $du is not set and returns 0.
> 
> i would prefer to leave setting if du to the script.  it is not a good
> idea to embed too much functionality to functions.  so there should be a
> function or transformation to remove extract and remove the received
> parameter in addition of one that inserts the received parameter.

Well, as it's not so complex it makes sense. Just a question: is it easy to 
add a *URI* parameter into Contact header?


>  > However I would like to check how it works in this scenario:
>  >
>  >   UA1 --(NAT)-- Proxy1 ----- Proxy2 --(NAT)-- UA2
>  >
>  >
>  > - UA1 sends INVITE (private address in headers).
>  >
>  > - Proxy1 adds ";received" to Contact URI"
>  >   Contact: <sip:ua1 at PRIVATE_UA1;received=PUBLIC_UA1>
>  >
>  > - Proxy 2 checks NAT. It shouldn't inspect the Contact URI !!! or if so,
>  > it should also take into account the existance of "received" param!!!
>  > (first problem). If not, Proxy2 would also add its own ";received"
>  > param: Contact:
>  > <sip:ua1 at PRIVATE_UA1;received=PUBLIC_UA1;received=PROXY1>
> 
> i don't see a problem here.  proxy should only check nat on requests
> that it receives from UAs, not from other proxies, because it should be
> other proxies' job to take care of their own UAs.

Yes, right :)


-- 
Iñaki Baz Castillo <ibc at aliax.net>