Subject: [SIP] Contact in Methods

From: Dvir Oren <[email-masked]>
Date: Wed, 12 Jul 2000 19:04:02 +0300 (IDT)

When will a Contact header field be used when sent in Methods?  If I
receive an INVITE with a Contact, what should I do with it?

Is it used only if I initiate a new call leg?

Thanks for the help.

-- 
Dvir Oren               <[email-masked]>
Lucid VON Ltd.     <http://www.lucidvon.com>
9 Saloniki St.,        Tel-Aviv       Israel
Tel:  +972 3 644 3038  Fax:  +972 3 644 3039

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From: "Vijay K. Gurbani" <[email-masked]>
Date: Wed, 12 Jul 2000 13:36:48 -0500

> receive an INVITE with a Contact, what should I do with it?

Save it.  The caller is telling you that it can be directly reached at 
that address for subsequent transactions (such as a BYE).  If you
decide to accept the INVITE, you may include a Contact header in the
200 OK which may be used by the caller to send the ACK directly to you.

Having said that, attention needs to be paid to Route and Record-Route
headers as well.  If a proxy inserted a Record-Route header in a
request, you cannot bypass it completely by sending subsequent requests
directly to the Contact address.  The RFC outlines how to construct
Route headers from Record-Route and Contact headers to route subsequent
requests.  See sections 6.33, 6.37 for that.  For an overview of 
Contact and its usage in requests and responses, see sections 6.13 and 
section 11.  These sections pertain to the June 9th 2000 bis draft.  I
think the FAQ also has some information on Contact headers and routing.

Regards,

- vijay
-- 
Vijay K. Gurbani  [email-masked] [email-masked] [email-masked]
IN Architecture and Internet Software Group
Lucent Technologies/Bell Labs Innovations, 263 Shuman Blvd, Rm 1A-418
Naperville, Illinois 60566  Voice: +1 630 224 0216 Fax: +1 630 713 0184