Subject: RE: [Sipping] Expert review of draft-ejzak-sipping-p-em-auth-00.t xt

From: "Ejzak, Richard P (Richard)" <[email-masked]>
Date: Tue, 18 Apr 2006 10:43:00 -0500

David R Oran wrote:
> On Apr 18, 2006, at 9:12 AM, Paul Kyzivat wrote:
> > Note that I am *not* opposed to service providers charging for  
> > their services. If the stated purpose of this header was to  
> > determine whether to charge for early media then I would have no  
> > problem. Nor would I have a problem with a mechanism by which a UA  
> > could ask to have early media blocked in cases where it would  
> > otherwise be charged for it.
> >
> This seems a superior semantic to what has been proposed.

This is just a particular (and reasonable) early media policy.  One would still require some mechanism to signal the use of authorized (free) early media through the network to implement such a policy.  (And the P-header in the draft would enable one to implement such a policy.)

I see no value in constraining the draft to only support the policy you propose, however.  It wouldn't be "local policy" then, would it?

Richard

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From: David R Oran <[email-masked]>
Date: Tue, 18 Apr 2006 15:27:39 -0400

On Apr 18, 2006, at 11:43 AM, Ejzak, Richard P (Richard) wrote:

> This is just a particular (and reasonable) early media policy.  One  
> would still require some mechanism to signal the use of authorized  
> (free) early media through the network to implement such a policy.   
> (And the P-header in the draft would enable one to implement such a  
> policy.)
>
Why would you ever block it if there were no consequences? You could  
always drop early media on the floor if you didn't want to play it  
out. That's the whole point of Paul's line of reasoning.

> I see no value in constraining the draft to only support the policy  
> you propose, however.  It wouldn't be "local policy" then, would it?
>
It could be local or not depending on who paid attention. In fact, we  
might be able to do this with a caller pref and avoid a header  
altogether.

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From: Paul Kyzivat <[email-masked]>
Date: Tue, 18 Apr 2006 19:02:50 -0400

Ejzak, Richard P (Richard) wrote:
> This is just a particular (and reasonable) early media policy. 
> One would still require some mechanism to signal the use of
> authorized (free) early media through the network to implement
> such a policy.  (And the P-header in the draft would enable one
> to implement such a policy.)

Yes, it could be used for that purpose.

> I see no value in constraining the draft to only support the
> policy you propose, however.  It wouldn't be "local policy"
> then, would it?

If the policy is "local" then why does the draft single out a particular 
policy at all?

    "... if the proxy controls the gating of early media in both
    directions for the User Agent Client, it SHALL use the contents of
    the P-Early-Media header to gate the early media according to the
    ..."

That in fact *excludes* the policy I suggested that leaves it to the UA 
to request that the gate be closed.

If a policy is to be mentioned at all then I hope it can give some 
balance and insight into different policies and their pros/cons.

	Paul

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From: "Jeroen van Bemmel" <[email-masked]>
Date: Wed, 19 Apr 2006 06:39:28 +0200

Paul,

> That in fact *excludes* the policy I suggested that leaves it to the UA to 
> request that the gate be closed.
>

You mean "UAC" here, right? So you're suggesting to allow P-Early-Media to 
appear in requests too? (currently only provisional responses to INVITE)

Regards,

Jeroen

---

From: Paul Kyzivat <[email-masked]>
Date: Wed, 19 Apr 2006 09:34:37 -0400

Jeroen van Bemmel wrote:
> Paul,
> 
>> If the policy is "local" then why does the draft single out a 
>> particular policy at all?
>>
>> That in fact *excludes* the policy I suggested that leaves it to the 
>> UA to request that the gate be closed.
>>
> 
> You mean "UAC" here, right? So you're suggesting to allow P-Early-Media 
> to appear in requests too? (currently only provisional responses to INVITE)

Yes, I meant UAC. I was suggesting that it should ultimately be up to 
the UAC whether early media will be accepted, with the potential that if 
early media is accepted then it *might* result in a charge. To handle 
the case where the UAC isn't willing to pay a charge to receive the 
early media, there could be *some* mechanism by which the UAC could 
request that early media not be delivered if it will result in a charge.

I suppose one mechanism might be for the UAC to include the 
P-Early-Media header in the original request. But that doesn't give 
enough information - it could only authorize acceptance in all cases. 
Would probably need a way to say "I will take early media if it is free, 
but not if it will cost me."

Putting in a negotiation mechanism could have some other benefits as 
well. For instance, it might be reasonable to say "I can take early 
media as long as I don't get concurrent early media from multiple 
sources." Then a forking proxy may be able to adjust its behavior and 
the authorization so that there are never multiple UASs doing early 
media in parallel.

	Paul