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

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Wed, 5 Apr 2006 09:50:12 +0200

Hi Fredrik,

I wonder if it would be good to combine the checking of the reg-id and
Call-ID then.

Because, even if the UA does NOT reboot, it is still going to send
periodical registration refreshes, without updating the flow
characteristics (source port etc). 

So, if the reg-id AND Call-Id are identical from the previous register
the receiver would assume this is just a refresh. 

But, if the reg-id is identical, but the Call-Id is NOT, from the
previous register (the Call-Id must change after the reboot, in order
not cause problems with the Cseq check by the receiver) the receiver
would assume that a flow has been "replaced" (e.g. due to a UA reboot).

Regards,

Christer

-----Original Message-----
From: Fredrik Thulin [mailto:[email-masked]] 
Sent: 4. huhtikuuta 2006 16:57
To: Christer Holmberg (JO/LMF)
Cc: [email-masked]
Subject: Re: [Sip] Outbound: Questions on reg-id

On Tuesday 04 April 2006 15:48, Christer Holmberg (JO/LMF) wrote:
> Hi,
>
> Ok, I missed that text. I appologize for that.
>
> But, then, if I send a REGISTER with reg-id=1, then I reboot, then I 
> send a REGISTER with reg-id=1 again, how will the registrar know I 
> have rebooted?

I'd say it doesn't know that you rebooted, but it knows that you want to
replace the entry in the location database from your first REGISTER with
the one in your second. This means that you don't want to use the flow
from your first REGISTER either.

To better understand the benefit of this, picture the example with the
first REGISTER going from IP tcp:192.0.2.11:1234 (source port 1234) with
reg-id=1. Then a reboot and then your second REGISTER from
tcp:192.0.2.11:1111 (new source port) but once again reg-id=1.

Oh, and it's not really just saying that you "want" the registrar to
stop using the old flow, you indicate to the registrar that it MUST stop
using the old flow but may very well use the new flow you just
initiated.

/Fredrik

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---

From: Fredrik Thulin <[email-masked]>
Date: Wed, 5 Apr 2006 10:57:59 +0200

On Wednesday 05 April 2006 09:50, Christer Holmberg (JO/LMF) wrote:
> Hi Fredrik,
>
> I wonder if it would be good to combine the checking of the reg-id
> and Call-ID then.
>
> So, if the reg-id AND Call-Id are identical from the previous
> register the receiver would assume this is just a refresh.
>

I think these are issues you have to deal with when implementing 
Outbound in a Registrar (something I have done), but not something that 
needs to be explained further in the standard. If Outbound _replaced_ 
RFC3261 #10.3 then it would have to be spelled out, but it doesn't - it 
just extends it.

In my implementation I didn't touch the RFC3261 10.3 processing. I just 
added functionality to remove any contacts in the location database 
whose instance-id and reg-id matched the contact (from a REGISTER) 
currently being processed to the code that already removed any bindings 
in the location database for the current AOR whose URI matched the 
contact being processed.

After SIPIT I hope to be able to tell you if this works in practice and 
not only in theory (theory plus test cases).

/Fredrik