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

Iñaki Baz Castillo ibc at aliax.net
Wed Nov 12 10:16:18 CET 2008

2008/11/12 Johansson Olle E <oej at edvina.net>:

>> I suggest you to look for "To" header in RFC3261 until finding it, but
>> trust me :)

Well, this info is in:

- To

- To and Request-URI

- Also: 4 Overview of Operation
  "To contains a display name (Bob) and a SIP or SIPS URI
   (sip:bob at biloxi.com) towards which the request was originally

> 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.

Yeah, RFC 4916 page 4:

     "Usage of the URI from the To and From fields in the original
      request within subsequent requests is done for backwards
      compatibility with RFC 2543 [6], which used the URI for dialog
      identification.  In this specification, only the tags are used for
      dialog identification.  It is expected that mandatory reflection
      of the original To and From URI in mid-dialog requests will be
      deprecated in a subsequent revision of this specification."

As you say, I think the proxy is not able to change the From/To URI,
just the UA's can do it.


Iñaki Baz Castillo
<ibc at aliax.net>

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