Subject: Re: [sipcore] Reuse of Sip Call-Id question..

From: "Attila Sipos" <[email-masked]>
Date: Fri, 5 Jun 2009 16:33:53 +0100

>>is this in violation of the RFC?

Yes, it's a violation.

If a new call is starting, a new call-ID must be used.

RFC3261 is very clear on this...

   Call-ID contains a globally unique identifier for this call,
   generated by the combination of a random string and the softphone's
   host name or IP address.

And...

   In a new request created by a UAC outside of any dialog, the Call-ID
   header field MUST be selected by the UAC as a globally unique
   identifier over space and time unless overridden by method-specific
   behavior. 

Each new request after the 486 is outside of any dialog.

(And there is nothing method-specific here which allows your described
behaviour)

Regards,

Attila

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Cahall, Glenn
Sent: 05 June 2009 16:18
To: Paul Kyzivat
Cc: [email-masked]
Subject: Re: [sipcore] Reuse of Sip Call-Id question..

Paul,

Thanks for the response.

Once I read your response, I felt that I needed to explain the situation
in more detail.

Customer is sending us an INVITE, our response is a 486 BUSY.  This
exact scenario (all with same TNs) repeats itself 100+ times over the
next 90 seconds or so.  All 100+ INVITEs contain the same Call-Id.
However, tag value in the From field is different.

So....now that you know more about the situation....is this in violation
of the RFC?

Also, during our discussions on the topic, we argued whether or not
Call-Id could be reused.  In short, as stated before, even if the
initial call was successful, they believed that as soon as that call was
completed, they were free to use the exact same Call-Id on the very next
call.

Thanks for your input,
Glenn

-----Original Message-----
From: Paul Kyzivat [mailto:[email-masked]]
Sent: Thursday, June 04, 2009 6:13 PM
To: Cahall, Glenn
Cc: [email-masked]
Subject: Re: [sipcore] Reuse of Sip Call-Id question..

Cahall, Glenn wrote:

> We have customer UAs that are reusing the same Sip Call-Id for 
> multiple call attempts into our network.
> 
> After reviewing the Sip RFC 3261, both myself and my team concluded 
> that this was a clear violation of the spec.  based on the following 
> verbiage...
...
> However, some voice engineers are stating that the definition of 
> "globally unique over time and space"  means only during the context 
> of a given call.  Therefore, once this context is over....Sip Call-Id 
> can in fact be reused in the very next context.

:-)

I would have thought that "globally unique over time and space" was
pretty clear. I don't know how you can get from there to: "only during
the context of a given call".

In fact, "only during the context of a given call" is the *exception*,
during which the same callid *may* be reused. Specifically, if you make
several different INVITE attempts in pursuit of the same "call" then
they may have the same callid, but must be distinguished by different
from-tags. (This would typically come up if an initial request resulted
in a 3xx response, and the UAC is recursing on the Contacts in the 3xx
in an attempt to complete the call.)

These guys have no legs to stand on, if you are accurately describing
the situation.

	Thanks,
	Paul
_______________________________________________
sipcore mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/sipcore

---

From: "Attila Sipos" <[email-masked]>
Date: Fri, 5 Jun 2009 16:41:27 +0100

After seeing Paul's answer, I agree that it could be
argued that all the INVITEs after the 486
responses are different attempts of the same call.

I think their behaviour might work in some cases but I suspect
interop success will be lower than if they modified
their behaviour to use a new call-ID each time.

As for re-using the call-ID for different calls... definitely NO.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Attila Sipos
Sent: 05 June 2009 16:34
To: Cahall, Glenn; Paul Kyzivat
Cc: [email-masked]
Subject: Re: [sipcore] Reuse of Sip Call-Id question..

Yes, it's a violation.

And...

Regards,

Attila

-----Original Message-----

Paul,

Thanks for the response.

Thanks for your input,
Glenn

-----Original Message-----
From: Paul Kyzivat [mailto:[email-masked]]
Sent: Thursday, June 04, 2009 6:13 PM
To: Cahall, Glenn
Cc: [email-masked]
Subject: Re: [sipcore] Reuse of Sip Call-Id question..

...

:-)

	Thanks,
	Paul