[asterisk-bugs] [Asterisk 0017020]: SIP response 415 "Unsupported Media Type" when using G729

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
====================================================================== 
https://issues.asterisk.org/view.php?id=17020 
====================================================================== 
Reported By:                jonaskellens
Assigned To:                
====================================================================== 
Project:                    Asterisk
Issue ID:                   17020
Category:                   Codecs/General
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     feedback
Asterisk Version:           Older 1.4 - please test a newer version 
JIRA:                       SWP-1083 
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
====================================================================== 
Date Submitted:             2010-03-13 10:23 CST
Last Modified:              2010-04-10 13:35 CDT
====================================================================== 
Summary:                    SIP response 415 "Unsupported Media Type" when using
G729
Description: 
Using Asterisk 1.4.25.1

Grandstream IP-phone has codecs G729, alaw, GSM.
Zoiper softphone has codecs alaw, GSM.

sip.conf peer definition grandstream :
disallow : all
allow : G729;alaw;GSM

sip.conf peer definition zoiper :
disallow : all
allow : alaw;GSM

When calling from zoiper softphone to Grandstream, the codec used is
alaw.

When calling from Grandstream to Zoiper, the call fails with SIP response
415 "Unsupported Media Type".

Why is it that Asterisk does not negotiates about the alaw-codec between
the Grandstream, Asterisk itself and the Zoiper softphone.

Is it normal behaviour that when one of the 2 SIP endpoints does not have
a G.729 license and Asterisk does not hold the license to translate from
G729 codec to another, the call fails ?
====================================================================== 

---------------------------------------------------------------------- 
 (0120248) pabelanger (manager) - 2010-04-10 13:35
 https://issues.asterisk.org/view.php?id=17020#c120248 
---------------------------------------------------------------------- 
I'll give this a shot, however I'm _not_ an expert by any means.

According to rfc3261.txt, 8.1.3.5 Processing 4xx Responses:
---
   If a 415 (Unsupported Media Type) response is received (Section
   21.4.13), the request contained media types not supported by the UAS.
   The UAC SHOULD retry sending the request, this time only using
   content with types listed in the Accept header field in the response,
   with encodings listed in the Accept-Encoding header field in the
   response, and with languages listed in the Accept-Language in the
   response.
---

However, looking at the trace I do not see the 'Accept' header field. 
According to 8.2.3 Content Processing

---
   ... the UAS MUST reject the request with a 415
   (Unsupported Media Type) response.  The response MUST contain an
   Accept header field listing the types of all bodies it understands,
   in the event the request contained bodies of types not supported by
   the UAS.
---

That being said, I believe issue is a result of the Zoiper softphone.
However, there _may_ be an issue here with asterisk, because we see:

   [Mar 19 09:19:28] VERBOSE[18601] logger.c: [Mar 19 09:19:28]
Capabilities: us - 0x10a (gsm|alaw|g729), peer - audio=0x10a
(gsm|alaw|g729)/video=0x0 (nothing), combined - 0x10a (gsm|alaw|g729)

however, only set G729 in the sdp:

   [Mar 19 09:19:28] VERBOSE[18634] logger.c: [Mar 19 09:19:28] Adding
codec 0x100 (g729) to SDP

I would think, at a minimum we should be also setting alaw, and gsm. But
like lmadsen said 'ntil someone better equipped can respond'. :) 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2010-04-10 13:35 pabelanger     Note Added: 0120248                          
======================================================================