[SIPForum-discussion] Can we use the same URL in From header of UA(User Agent) Message (REFER)to add in Contact header to bulid same message(in proxy)

[ashok.pitambar at wipro.com]

Hi Tomasz Zieleniewski, 
 
    I got below reply from one of my senior ravi, 
 
                            i have seen and read the threads on SIP and
SIP-Implementers mailing list with your questions.
I agree with the response that has been posted. The purpose and nature
of From header is different from that of Contact header.
While From is a general Address of Record, while Contact header contains
address of one specific instance of the entity identified by that AOR.
 
For example, while sip:ravishankar.shiroor at wipro.com
<mailto:ravishankar.shiroor at wipro.com>  is a general AOR to reach me,
sip:ravishankar.shiroor at ravilaptop.parramattaoffice.wipro.com is a
specific instance at which i am currently reachable, and that will be
what the Contact header contain. 3261 definitions of the terms should
give you the accurate definition.
 
So if you use value from From header to populate Contact, there is no
guarantee that you will reach the same instance. You might end up
reaching my home phone or mobile or any other instance.
As has been indicated on the mailing lists also, if you really want to
lenient and do it, you can go ahead, but it may not work consistently.
 
I do not know exactly in what situation and as what entity in the
dialog/session you are asking this question. 
If you know the exact instance in which you are doing this, and you know
that AOR in From will definitely lead you (or anybody who received the
Contact) to that instance itself, then you could still do it. You will
have to analyse the situation closely before making the call.
 
Same thing applies for Subscribes too.
 
 
Regards ,
ASHOK PITAMBAR
 

________________________________

From: Tomasz Zieleniewski [mailto:tzieleniewski at gmail.com] 
Sent: Thursday, February 12, 2009 1:34 PM
To: Ashok Pitambar (WT01 - Telecom Equipment)
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Can we use the same URL in From
header of UA(User Agent) Message (REFER)to add in Contact header to
bulid same message(in proxy)


Hi,

Yes, of course.
REFER message can be sent outside of the dialog (in which case it
creates it's own one)
So the request must contain the Contact header field which contains
global scope SIP or SIPS URI 
which is an address where the UAC would like to be contacted for
subsequent requests in the dialog. 
UAS uses Contact header from the request as the remote target value.

Regards
Tomasz Zieleniewski


2009/2/10 <ashok.pitambar at wipro.com>


	Hi All ,  
	 
	
	Can we use the  same URL in From header of  UA(User Agent)
Message (REFER)to add in Contact header to bulid same message ?.
	 
	
	Check  this folw ...
	 
	UA(A)                               ---->PROXY(domain1.com)
----->PROXY(domain2.com)-            --->UA(B)
	 
	 
	REFER                             ----->               REFER
-------->      REFER                      --------> REFER

	From A at domain1.com        From A at domain1.com
>From A at domain1.com                    From A at domain1.com
	 To B at domain2.com <mailto:B at domain2.com>            To
B at domain2.com <mailto:B at domain2.com>                            To
B at domain2.com <mailto:B at domain2.com>                         To
B at domain2.com <mailto:B at domain2.com>  
	                                    Contact:A at domain1.com
<mailto:A at domain1.com>         Contact:A at domain1.com
<mailto:A at domain1.com> :       Contact:A at domain1.com
<mailto:A at domain1.com> :
	 
	 
	 
	Regards ,
	ASHOK PITAMBAR

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