Re: [Stox] I-D Action: draft-ietf-stox-7248bis-09.txt

[Peter Saint-Andre <[e-mail]>]

On 8/29/16 4:56 PM, Ben Campbell wrote:
> Hi Peter,
>
> I'm going to try to be more responsive on this, and break the apology
> loop :-)

Likewise!

> I agree we are zeroing in on things here. I think, with this version, I
> can better clarify my remaining concern. (I think it's the only thing
> left.)
>
> 5.2.3 talks about canceling a presence authorization. But from Romeo's
> perspective, it does do that; it only cancels the notification session.
> SIP has no way for Juliet to explicitly say "I want my permission to see
> Romeo's presence info to go away". If Juliet never wants to be notified
> again, she simply doesn't subscribe again. Maybe Romeo's system has some
> policy that ages out such authorizations over time, but that's not
> really relevant to this draft. (It's also possible for Romeo to
> unilaterally cancel that authorization, but that's probably more detail
> than is needed here.) In simpler terms, Romeo's presence server asks him
> if he wants to let Juliet subscribe the first time she tries. For future
> subscriptions, it won't ask. If Romeo later decides he prefers less
> star-crossed relationships, he can withdraw that permission. Other than
> than the initial subscription request, Juliet has no say in the matter.
>
> This is also true for _requesting_ authorization. For example, the only
> thing that makes 5.2.1 into a request for authorization (on the SIP
> side) is the fact that Juliet is subscribing for the first time. (I'm
> not saying 5.2.1 needs to change; I just mention this for background).
>
> Likewise in 5.3.3, Romeo is not asking to be deauthorized. He's just
> asking to end the notification session. Now that may not matter, he just
> gets re-authorized next time hie sends a SUBSCRIBE request. But he might
> be surprised to find that Juliet thought he had requested to be
> deauthorized. (Not to mention, that Juliet might feel, well,
> "unfriended" :-)  )
>
> This all goes counter to the statement in the 2nd to last paragraph of
> 5.1 that SIP presence authorizations are managed with SUBSCRIBE
> requests. The real situation is that the watcher (Juliet) doesn't manage
> these authorizations at all--they are unilaterally managed by the
> presentity (Romeo). A SUBSCRIBE request from Juliet may cause Romeo to
> be notified that he needs to make an authorization decision if he has
> not previously given permission.

Your description really clarified things for me, so thanks!

> So, how to fix this? I'm not sure I have the answer. But one approach
> might be to extend 5.1 to be more clear about the difference in
> authorization models, then have sections 5.2.x and 5.3.x talk more about
> notification sessions than authorization, but mention authorization
> state changes in the commentary about the message detail as needed.

Yes, that seems sensible. I will work on an updated I-D along those 
lines very soon.

Peter