2 Oct
2007
2 Oct
'07
4:57 p.m.
I should have Cc'd this to the list...
-------- Original Message --------
Subject: Re: [Serusers] How to change INVITE From field
Date: Tue, 02 Oct 2007 13:57:49 +0200
From: Olaf Bergmann <Olaf.Bergmann(a)freenet.ag>
Organization: Freenet Cityline GmbH
To: SIP <sip(a)arcdiv.com>
References: <b222g3dmntvc38gk3v2uq7vau6vmfcjem1(a)4ax.com>
<4701F388.7020109(a)freenet.ag> <470217DF.9020607(a)arcdiv.com>
SIP wrote:
[RFC 2543]
The implication of this is that the ENTIRE From/To
headers are not
necessarily immutable, as the tag is used to identify them as unique.
Well, transaction matching in RFC 2543 has used the nameaddr part of
the From/To headers, therefore implementations were required not to
change these. Tags at that time have been introduced primarily for
dealing with forked requests.
In RFC 3261, this has been re-designed mainly for robustness of
transaction matching. Since there were many pre-3261
implementations, the requirement of immutable From and To headers is
still valid. (Nowadays, people start discussing if this is still
necessary.) To ensure interoperability, carriers typically use
dialog-stateful intermediaries (back-to-back user agents) to change
these headers.
The question is, is there something elsewhere which
contradicts this
(and therefore enforced the rule of immutable From/To headers), or is
this just a SER idiosyncrasy? If it's just a SER thing, might it not be
different in other systems (something we might have to watch out for),
or might it not be coded around within SER to allow modification of the
From header?
IMHO it is a SER thing, and you could probably change the function
for branch creation (the problem is that you must find another way
for stateless generation of recognizable branch tags).
Regards,
Olaf