[Asterisk-Users] Cisco/Asterisk codec negotiation problems

[Alistair Cunningham]

All,

I'm working on an Asterisk 1.0.7 system that is acting as a B2BUA SIP 
gateway. "canreinvite=no" is set in the global section of sip.conf, and 
it's important that it be there. I have

Cisco ---> Asterisk ---> Multiple destinations

Some destinations support both G711 and G729, but some only support 
G729, and some do not support G729.

On Cisco, I have:

voice class codec 3
  codec preference 1 g711alaw
  codec preference 2 g711ulaw
  codec preference 3 g729r8

On Asterisk, I have (irrelevant parts snipped) in sip.conf:

[g729only]
type = friend
host = 192.168.1.1
disallow = all
allow = g729

[g711only]
type = friend
host = 192.168.1.2
disallow = all
allow = alaw
allow = ulaw

[cisco]
type = friend
host = 10.1.1.1
disallow = all
allow = alaw
allow = ulaw
allow = g729

I've also tried without the disallow and allows in [cisco], and with 
them in [general].

When I call from the Cisco to g711only via Asterisk, the call works. 
When I call from  the Cisco to g729only via Asterisk, I get:

Apr 16 15:56:41 NOTICE[11297]: Unable to find a path from g729 to alaw
Apr 16 15:56:41 NOTICE[11297]: Unable to find a path from alaw to g729

In a SIP trace, in the INVITE from Cisco to Asterisk, I see:

a=rtpmap:8 PCMA/8000.
a=rtpmap:0 PCMU/8000.
a=rtpmap:18 G729/8000.
a=fmtp:18 annexb=no.
a=rtpmap:101 telephone-event/8000.
a=fmtp:101 0-16.

In the INVITE from Asterisk to g729only:

a=rtpmap:8 PCMA/8000.
a=rtpmap:0 PCMU/8000.
a=rtpmap:18 G729/8000.
a=rtpmap:101 telephone-event/8000.
a=fmtp:101 0-16.
a=silenceSupp:off - - - -.

In the 200 OK from g729only:

a=rtpmap:18 G729/8000/1.
a=rtpmap:101 telephone-event/8000.
a=fmtp:101 0-15.

When Asterisk gets this message, it replies to g729only with a ACK then 
a BYE, and sends a 403 Forbidden to the Cisco. At no point does Asterisk 
send any message to the Cisco suggesting that Alaw is not acceptable or 
that G729 is allowed.

My question to you, Asterisk-users, is why Asterisk drops the call when 
both sides have offered G729? It seems to think that the Cisco is Alaw 
only; this is the default codec on Cisco, but it is offering other 
codecs as well.

I've tried various settings. I can also make G729 work but G711 fail, 
but can't do both at the same time. I've also tried the following on Cisco:

voice class codec 2
  codec preference 1 g729r8
  codec preference 2 g729br8
  codec preference 3 g723r63
  codec preference 4 g723r53
  codec preference 5 g723ar63
  codec preference 6 g723ar53
  codec preference 9 g711alaw
  codec preference 10 g711ulaw
  codec preference 11 gsmfr
  codec preference 12 gsmefr

With the dial-peer changed to use it, but this doesn't help either.

(Hostnames and IP addresses changed to protect the guilty, i.e. me)

-- 
Alistair Cunningham,
Integrics Ltd,
+44 (0)7870 699 479
http://integrics.com/