[OpenSIPS-Users] modify TO field in the SIP message header

Johansson Olle E oej at edvina.net
Wed Nov 12 10:01:58 CET 2008

12 nov 2008 kl. 09.58 skrev Iñaki Baz Castillo:

> 2008/11/12 Alex Massover <alex at jajah.com>:
>> Hi!
>> Can you please point me, where exactly is it written in RFC?
>> I'm also in doubts about changing To header.
> Well, not sure where exactly, but I can sure 300% that To shouldn be
> NEVER modified by a proxy or UA (except the UAS who adds the To_tag,
> of course).
> I suggest you to look for "To" header in RFC3261 until finding it, but
> trust me :)

This was actually mandated by SIP v1.0, so you have to go further back
than 3261. SIP v1.0 used From and To headers as identifiers for a call.
SIP v2.0 kept this for backwards compatibility, but moved to using
tags as identifiers.

There's a recent RFC that changed this again, but I still don't
think the Proxy is allowed to change From/To headers,
only the UA. This is for caller ID updates. The RFC might
allow proxy changes, but that needs to be checked.


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