Hi Alex,

It´s not really my idea and I also think it´s not the best way, but I have to 
search for options to do this.

Thanks,
Hanns

 


---Ursprüngliche Nachricht-----
Von: Alex Balashov [mailto:abalas...@evaristesys.com] 
Gesendet: Mittwoch, 24. November 2010 11:34
An: Johannes Wagner-Meingassner
Cc: sr-users@lists.sip-router.org
Betreff: Re: [SR-Users] Remove a CODEC in the Invite

Johannes,

On 11/24/2010 05:19 AM, Johannes Wagner-Meingassner wrote:

> I have to remove the Transparent Codec in the INVITE-Message to a 
> dedicated SIP-Client, because the Client can not work with it.
> What do you think is the best methode to do this?

While the motive is understandable, this is a bad idea.  Proxies are supposed 
to relay messages, not modify them.  There are certain fields of a message (for 
example, the Request URI in an initial request) that they can modify, and they 
can add additional headers, but in general, that is not their purpose an.d 
their modification capabilities are formally very restricted.  It is 
fundamentally contrary to the purpose of a proxy in every way to do something 
like modify the SDP body.

On a practical level, the problem with modifying the SDP offer is that without 
stateful reversion applied to every answer sent (rather in the way that 
uac_replace_from() and 'topoh' work for other data), the sender of the offer is 
fully entitled to refuse an answer whose content does not reflect the original 
offer sent (since modifying SDP on the proxy would be opaque to the sender).

You really need to use a B2BUA for something like this.

--
Alex Balashov - Principal
Evariste Systems LLC
1170 Peachtree Street NE
12th Floor, Suite 1200
Atlanta, GA 30309
Tel: +1-678-954-0670
Fax: +1-404-961-1892
Web: http://www.evaristesys.com/

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