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

Klaus Darilion klaus.mailinglists at pernau.at
Wed Nov 12 10:47:01 CET 2008

Iñaki Baz Castillo schrieb:
> 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 :)

"Never changing From/To headers" is in RFC 3261 for compatibility with 
RFC 2543 which used the whole header for dialog matching. RFC 3261 only 
uses the tags - thus changing from/to is possible.

Recently there was an RFC published which explicitly changes the from 
and to header (I can not remember the RFC number) with the conclusion 
that there shouldn't be any RFC 2543 clients anymore.

Nevertheless, if there is a component which does routing based on To it 
is buggy.


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