Subject: [Sipping] Consent: Do we need <operations>?

From: Adam Roach <[email-masked]>
Date: Mon, 07 Nov 2005 16:17:55 -0800

During today's meeting, Gonzalo floated the prospect of removing the 
<operations> section from permissions document. Cullen mentioned that he 
recalled that someone had, in the past, floated the requirement that we 
be able to distinguish between instant messaging and voice 
communications, and that the <method> mechanism may provide a means for 
meeting this requirement.

I verified offline that Cullen does not, himself, assert this as a 
requirement.

In the interest of simplifying the consent work, I'd like for anyone who 
actually has this behavior as a requirement to please repeat their 
requirement. In particular, I think it would be useful -- in the context 
of MSRP sessions being established using INVITE messages -- whether the 
mechanism of making decisions on a per-method basis actually fulfills 
the posited requirements.

Alternately, if no one actually asserts this as a requirement, I agree 
with Gonzalo that it represents unnecessary complication that can be 
removed.

/a

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From: Paul Kyzivat <[email-masked]>
Date: Mon, 07 Nov 2005 20:08:48 -0500

I think it is reasonable to want to grant permission for IM but not 
voice. If MSRP is used, then restricting by method isn't a viable way to 
do this.

The alternative is to grant permission if there is some combination of 
media that are allowed. Then the callee would just have to reject offers 
of media it doesn't want to permit. This seems like it might be good 
enough, since if it desires it can refuse an invite without alerting, or 
simply refuse the undesired media and alert based on the rest if that 
seems reasonable.

So I agree that restricting on method doesn't seem very important.

	Paul

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From: "Jeroen van Bemmel" <[email-masked]>
Date: Tue, 8 Nov 2005 07:45:22 +0100

Adam,

What about a mechanism for the relay to mark the request as having been 
passed through it (with consent)?
The relay could e.g. use "Proxy-Identity" along the lines of Identity 
(including a 'consented' flag covered by some digest), such that the UAC 
knows to which messages it consented (and possibly refuse all others)?

Regards,

jeroen

----- Original Message ----- 
From: "Paul Kyzivat" <[email-masked]>
To: "Adam Roach" <[email-masked]>
Cc: <[email-masked]>
Sent: Tuesday, November 08, 2005 2:08 AM
Subject: Re: [Sipping] Consent: Do we need <operations>?

>I think it is reasonable to want to grant permission for IM but not voice. 
>If MSRP is used, then restricting by method isn't a viable way to do this.
>
>> mechanism of making decisions on a per-method basis actually fulfills the 
>> posited requirements.
>>

---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 08 Nov 2005 13:58:15 -0500

> voice. If MSRP is used, then restricting by method isn't a viable way to 

I think we need to separate the use cases here.

The main one that is the focus of this work are relays outside of your 
administrative domain, to which you have been added as a target. These 
relays have little incentive at all to do much work on your behalf. The 
are only incented to send or not send traffic in order to protect 
themselves against amplification attacks. Doing filtering on behalf of 
the subscriber seems to go beyond what they might be willing to do. As 
such, I think we should restrict this to just yes/no.

If there is a desire for more substantive filtering, that should be 
treated more like a feature that runs on behalf of the recipient on sip 
servers in their own network. I think we decided that this was separate 
and not in scope here.

Thanks,
Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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From: Ben Campbell <[email-masked]>
Date: Tue, 8 Nov 2005 11:07:05 -0800

On Nov 8, 2005, at 10:58 AM, Jonathan Rosenberg wrote:

>
>
> Paul Kyzivat wrote:
>> I think it is reasonable to want to grant permission for IM but  
>> not voice. If MSRP is used, then restricting by method isn't a  
>> viable way to do this.
>
> The main one that is the focus of this work are relays outside of  
> your administrative domain, to which you have been added as a  
> target. These relays have little incentive at all to do much work  
> on your behalf. The are only incented to send or not send traffic  
> in order to protect themselves against amplification attacks. Doing  
> filtering on behalf of the subscriber seems to go beyond what they  
> might be willing to do. As such, I think we should restrict this to  
> just yes/no.
>
> treated more like a feature that runs on behalf of the recipient on  
> sip servers in their own network. I think we decided that this was  
> separate and not in scope here.
>

I concur with Jonathan on this one. The IM vs Voice question is  
usually more a matter of what I am willing to accept at a given point  
in time than it is who I am willing to allow to communicate with me  
at all. That seems like more a filtering or possibly presence  
application.

---

From: Paul Kyzivat <[email-masked]>
Date: Tue, 08 Nov 2005 14:10:27 -0500

at end.

	Paul

Jonathan Rosenberg wrote:
>> voice. If MSRP is used, then restricting by method isn't a viable way 
>> to do this.
> 
> 

I don't have a strong opinion here, but I am trying to reason from 
existing practice. Today, when I am lucky, I can opt in/out of 
solicitations, often on a media-type basis: phone, email, snail mail. 
This may just be an artificial distinction based on technological 
stovepipes, but it seems like a helpful distinction. Those companies 
that have any interest in keeping customers happy seem willing to track 
this distinction.

Perhaps there is no reason to make this kind of media-specific 
distinction in sip. For instance I don't know that I would care about a 
distinction between voice and video. But in my own mind I do draw a 
useful distinction between IM and voice. I'm uncertain how significant 
this is, and would like to hear what others think.

	Paul

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From: "Dale R. Worley" <[email-masked]>
Date: Tue, 08 Nov 2005 20:05:01 -0500

> knows to which messages it consented (and possibly refuse all others)?

Perhaps further parameters on Via?

Dale

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From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 09 Nov 2005 02:39:48 -0500

If the request was consented, it would already contain the 
Permission-Upload header field. You can use this as an indication.

-Jonathan R.

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From: "Jeroen van Bemmel" <[email-masked]>
Date: Wed, 9 Nov 2005 09:42:11 +0100

Jonathan,

I am not sure if I understand, perhaps you mean the "Permission-Used" header 
(with a URI to the signed consent document)?

If so, I guess that would suffice. Something worth mentioning in security 
considerations? Should this be stated as a requirement? (i.e. a UAS MUST be 
able to verify whether it consented to a given request)

Jeroen