Subject: [SIP] Proxies modifying SDP

From: Bernie Hoeneisen <[email-masked]>
Date: Fri, 15 Dec 2000 18:55:43 +0200 (EET)

Hi!

I have question concerning the case, when SIP proxies modify SDP,
which is AFAIK against SIP principles, isn't it?

In the concrete case, proxies would be able to remove certain codecs
from the INVITE messages, depending on the current policy in the
network. (The UAS gets a subset of the codecs, which were originally
sent by the UAC.)

What impact does such a proxy behavior have to SIP? I can think of
problems with authentication and message integrity checking (UAC signs
message with its private key).

Are there any other problems? Any comments are appreciated.

cheers,
 Bernie

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From: Jean-Francois Mule <[email-masked]>
Date: Fri, 15 Dec 2000 09:29:29 -0800

> which is AFAIK against SIP principles, isn't it?
I do not think so.
Why is that *against* SIP principles?  What principles?'

> message with its private key).
It certainly depends on the security mechanism used.  For e.g., with the
simple basic md5, it does not cause any issue.

Jean-Francois