NEVER manipulate From/To so that tag=something disappears!!š Per RFC3261, a dialog is the combination of these two tags and Call-Id.š On branching and reINVITE, the Call-Id will stay the same, while the tags may change.š This is relevant for accounting, for keeping track of branches, failures, and is absolutely necessary for the UAs to recognize the dialog.
The old RFC uses the full content of From/To for the same purposes, thus manipulating From/To will break your backwards suport for UACs/UASs that do not support RFC3261. This means that in a closed-wall deployment and all UAS/UAC support RFC3261, you MAY manipulate From/To, but it's not recommended and may well end up biting you later...
g-)

Alexandr Dubovikov wrote: 
On Sat, Aug 26, 2006 at 07:55:41PM +0100, rcarvalho@iric.up.pt wrote:
  
I'm sceptic about the use of functions that replace parts of SIP messages,
because that way, will Ser still keep record of transactions? Won?t those
replacements affect Ser to recognise to whom route subsequent messages?

Regards,

Ricardo.
    

Yep, we already discused here about it one week ago. From, To and Call-ID make a 
Call Leg of transaction. I am not sure, but ser tm based only on Call-ID and
ignore To/From fields.



Wbr,