Subject: RE: [Sip] Outbound: Questions on reg-id

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Tue, 4 Apr 2006 15:10:40 +0200

Hi, 

>A few clarification questions on the reg-id parameter.
>
>The outbound draft (chapter 3.1) says that the reg-id can be used by 
>the registrar to determine that a user has rebooted.
>
>Q1: In order to achieve that you would have to make sure the value is 
>unique. Because, if you use value "1", then rebood, and then use 
>value"1" again I don't see what it will bring.
>
It may be a poor choice of words. What the registrar really needs to
know is that a new "connection" or "flow" is the same as a previous
"flow". 

[CHH] Again, why can't you use Call-Id for that?

>The only things in the Contact guarateed to be the same after a UA
reboots is the reg-id and sip-instance id.

[CHH] My understanding of the draft is NOT that the SAME req-id would be
used. Where is that said?

The draft says that when the UA registers multiple times, each
registration gets a unique reg-id value. But, it does not say anything
about re-usage the same reg-id values after a reboot.

>The UA might get a new IP Address from DHCP. The combination of reg-id
& sip-instance identify the specific "flow" so the 
>registar can locate existing binding.
>
>Q2: Doesn't the Call-ID, as defined by RFC3261 to be used with 
>registrations, provide the same functionaltity?
>
>Chapter 10.2.4 of RFC3261 says:
>
>"A UA SHOULD use the same Call-ID for all registrations during a single

>boot cycle. Registration refreshes SHOULD be sent to the same network 
>address as the original registration, unless redirected."
>
True, but the registrar still needs the sip-instance and reg-id to
locate the specific flow.

[CHH] I still don't see why we can't use Call-Id instead of reg-id.

Regards,

Christer

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---

From: Fredrik Thulin <[email-masked]>
Date: Tue, 4 Apr 2006 15:32:14 +0200

On Tuesday 04 April 2006 15:10, Christer Holmberg (JO/LMF) wrote:
...
> [CHH] My understanding of the draft is NOT that the SAME req-id would
> be used. Where is that said?
>
> registration gets a unique reg-id value. But, it does not say
> anything about re-usage the same reg-id values after a reboot.

							   "The
   reg-id sequence does not have to be sequential but MUST be exactly
   the same reg-id sequence each time the device power cycles or reboots
   so that the reg-id values will collide with the previously used
   reg-id values.  This is so the proxy can realize that the older
   registrations are probably not useful."

/Fredrik

---

From: "Bob Penfield" <[email-masked]>
Date: Tue, 4 Apr 2006 09:34:05 -0400

In section 4.2, it says:

   These ordinary registration requests MUST also add a distinct
   reg-id parameter to the Contact header field.  Each one of these
   registrations will form a new flow from the UA to the proxy.  The
   reg-id sequence does not have to be sequential but MUST be exactly
   the same reg-id sequence each time the device power cycles or
   reboots so that the reg-id values will collide with the previously
   used reg-id values.  This is so the proxy can realize that the
   older registrations are probably not useful.

If the reg-id changed, the registrar would have no way to know that the old 
binding was no good anymore.

cheers,
(-:bob

Robert F. Penfield
Chief Software Architect
Acme Packet, Inc.
71 Third Avenue
Burlington, MA 01803
[email-masked]

----- Original Message ----- 
From: "Christer Holmberg (JO/LMF)" <[email-masked]>
To: "Bob Penfield" <[email-masked]>; <[email-masked]>
Sent: Tuesday, April 04, 2006 9:10 AM
Subject: RE: [Sip] Outbound: Questions on reg-id

Hi,

Regards,

Christer