[asterisk-dev] udptl ports

[Joshua Colp]

James Cloos wrote:
> Does asterisk intend to try to do symmetric for udptl?

If you enable it in sip.conf as you would for RTP this will be enabled 
in the UDPTL stack as well.

> In a report which I received, ast 1.8 used the same port which it had
> been using to originate rtp also to originate the udptl.  (The other
> side used and advertised the same port in the re-INVITE negotiation
> which it had used and advertised in the initial INVITE.)

Asterisk won't send from the same port. They are two different ranges. 
If it went through a NAT, though, then the external mapping COULD reuse 
the port depending on how it operates.

As for the other side using the same port there's nothing to say it 
can't be done. A potential problem arises though in that there still 
might be RTP packets in flight causing the remote UDPTL stack to receive 
RTP and then UDPTL.

> I don’t see anything in the rfcs or in t.38 which requires that either
> send send from the same port it advertises to receive, but did I miss
> anything?

There's nothing to say you can't and nothing to say you must.

> Nor do not see any relevant differences between chan_sip in 1.8 vs 11,
> so is this expected?

Nothing has changed for this.

Cheers,

-- 
Joshua Colp
Digium, Inc. | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org