Re: [Stox] Review for stox-7248bis-02

Peter Saint-Andre - &yet <peter@andyet.net> Sun, 26 July 2015 21:23 UTC

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To: "Isomaki Markus (Nokia-TECH/Espoo)" <markus.isomaki@nokia.com>, "stox@ietf.org" <stox@ietf.org>, Ben Campbell <ben@nostrum.com>, "rjsparks@nostrum.com" <rjsparks@nostrum.com>
References: <9315d702a9534242b9c36b4b93e19a45@NOKWDCFIEXCH02P.nnok.nokia.com> <55AD1E2A.9060102@andyet.net> <c2f86c086d1240f789f1c9f096b6fa58@NOKWDCFIEXCH02P.nnok.nokia.com> <55B083ED.3090801@andyet.net>
From: Peter Saint-Andre - &yet <peter@andyet.net>
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Date: Sun, 26 Jul 2015 15:22:57 -0600
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Subject: Re: [Stox] Review for stox-7248bis-02
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I've posted -04 to address this feedback.

Peter

On 7/23/15 12:04 AM, Peter Saint-Andre - &yet wrote:
> Hi Markus, thanks for the continued review.
>
> On 7/22/15 6:30 AM, Isomaki Markus (Nokia-TECH/Espoo) wrote:
>> Hi Peter,
>>
>> I checked the revised draft (-03) and it addresses the issues I raised
>> below. But that brought up another thing still.  It's been really long
>> since I've been dealing with SIP Presence, but I think that the
>> message flows in 4.2.1 may still need a couple of clarifications:
>>
>> 1.)
>>
>> In SIP, if the subscription is not immediately authorized (neither
>> accepted or rejected), it is possible that a 200 OK response to the
>> SUBSCRIBE is sent immediately followed by a NOTIFY with subscription
>> state "pending". If the SIP User later on positively authorizes the
>> subscription, another NOTIFY with subscription state "active" is
>> generated. The potential "pending" state does not seem to be covered
>> in the current diagram, but it probably should be. The question is
>> just what happens in XMPP-to-SIP GW if it gets a NOTIFY with "pending"
>> subscription state. To my understanding the subscription state would
>> remain "neutral" on the XMPP side. Would that mean that the
>> XMPP-to-SIP GW would not send anything to the XMPP side in that case,
>> i.e. only a NOTIFY indicating subscription state as "active" would
>> cause the message (F10) to be triggered? In that case, maybe this kind
>> of addition would be enough:
>>
>> OLD:
>>
>>     In accordance with [RFC6665], the XMPP-to-SIP gateway SHOULD consider
>>     the subscription state to be "neutral" until it receives a NOTIFY
>>     message.  Therefore, the SIP user or SIP server at the SIP user's
>>     domain SHOULD immediately send a NOTIFY message containing a
>>     Subscription-State header [RFC6665] whose value contains the string
>>     "active" (see Section 5 below).
>>
>> NEW:
>>
>>     In accordance with [RFC6665], the XMPP-to-SIP gateway SHOULD consider
>>     the subscription state to be "neutral" until it receives a NOTIFY
>>     message.  Therefore, the SIP user or SIP server at the SIP user's
>>     domain SHOULD immediately send a NOTIFY message containing a
>>     Subscription-State header [RFC6665] with value "active" (see
>> Section 5
>>     below). In case the XMPP-to-SIP gateway initially receives one or
>> more
>>     NOTIFY messages with Subscription-State "pending", it MUST respond
>>     to them on the SIP side, but not generate any presence stanzas
>> towards the
>>     XMPP User.
>
> That it better. The only further change I would make is:
>
>     In accordance with [RFC6665], the XMPP-to-SIP gateway SHOULD consider
>     the subscription state to be "neutral" until it receives a NOTIFY
>     message with a Subscription-State header [RFC6665] whose value is
>     "active".
>
> Also, I think it would make sense to change SHOULD to MUST here.
>
>> 2.)
>>
>> If you look at RFCs 3856 and 3857, the typical scenario in SIP
>> presence is: There is a SIP Presence Server handling the subscriptions
>> to the presence event package. That is where the SUBSCRIBE (F2) in
>> 4.2.1 goes. But typically the Presence Server would not forward the
>> SUBSCRIBE to the SIP User in way shown in (F3). Instead, the Presence
>> Server and SIP User would interact via the 'presence.winfo' event
>> package (RFC 3857), to which the SIP User would be subcribed. So, when
>> the Presence Server gets a SUBSCRIBE to SIP User's Presence, it
>> generates a 'presence.winfo' NOTIFY the SIP User, who will that way
>> learn about the new subscription. The SIP User would then authorize
>> the subscription by some interaction (for instance using XCAP) with
>> the Presence Server. In this scenario, presence updates from the SIP
>> User would also not be sent as NOTIFYs, but as PUBLISH messages to the
>> Presence Server, who would then generate NOTIFYs to all active
>> subscribers.
>>
>> It is however possible that the Presence Server acts in a Proxy mode,
>> in which case (as far as I remember), it just passes the SUBSCRIBEs
>> and NOTIFYs through as in the current diagram in 4.2.1. If we don't
>> want to go into the more complex diagrams, it would suffice just to
>> say (already in terminology or in 4.2.1): "In these examples it is
>> assumed that the SIP Server acts as a proxy for Presence event package
>> and the actual Presence Agent resides with the SIP User."
>
> Yes, the latter seems reasonable. However, also pointing to RFC 3857
> seems like a good idea.
>
> Peter
>