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

Peter Saint-Andre <stpeter@stpeter.im> Wed, 14 September 2016 15:49 UTC

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From: Peter Saint-Andre <stpeter@stpeter.im>
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Subject: Re: [Stox] I-D Action: draft-ietf-stox-7248bis-09.txt
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On 9/14/16 9:24 AM, Peter Saint-Andre wrote:
> A few additional notes...
>
> On 9/12/16 8:36 PM, Peter Saint-Andre wrote:
>> Thanks for the feedback. Comments inline.
>>
>> On 9/12/16 8:26 AM, Ben Campbell wrote:
>>> Hi,
>>>
>>> A few comments inline.
>>>
>>> Thanks!
>>>
>>> Ben.
>>>
>>> On 12 Sep 2016, at 5:42, Saúl Ibarra Corretgé wrote:
>>>
>>>     Review time!
>>>     Page 10: " As described in Section 6
>>>     , the XMPP-to-SIP gateway also generates a
>>>     presence notification addressed to the XMPP user:
>>>     “
>>>     Should we say “if the NOTIFY contains a body” or is it obvious
>>>     enough? It’s possible the SIP user is offline, but the XMPP is user
>>>     is already authorised, so the NOTIFY will contain
>>>     Subscription-State: active, but no body.
>>>
>>> It's probably worth adding an example of how the the gateway might
>>> interpret an empty body. I assume that if this is the first NOTIFY in
>>> the dialog (notification session), the gateway would interpret that as
>>> unknown or possibly "closed". If previous NOTIFYs have in the same
>>> notification session, it should probably mean "no change".
>>
>> Good idea, will do.
>
>    As described in Section 6, if this first NOTIFY in the notification
>    session contains a body then the XMPP-to-SIP gateway also generates a
>    presence notification addressed to the XMPP user (if the NOTIFY does
>    not contain a body then the gateway would interpret it as unknown or
>    "closed"):
>
>>>     Page 11: "As can be seen, because SIMPLE does not
>>>     have a construct that enables a contact to cancel her presence
>>>     authorization,”
>>>     There is: remove the user from the corresponding XCAP rule. Next
>>>     time presence is requested, it will be denied. (the SUBSCRIBE dialog
>>>     still needs to be terminated though).
>>>
>>> The text is about the subscriber, not the presentity. So if Juliet
>>> subscribes to Romeo's presence, Romeo can change the authorization rule
>>> (via xcap or otherwise). But /Juliet/ cannot.
>>>
>>> I suppose "her authorization" can be a bit ambiguous. (If Romeo
>>> authorizes Juliet, whose authorization is it?)
>>
>> I was tempted to add "outbound" or "inbound" in all cases to make this
>> crystal clear...
>
> Changed to "cancel her outbound presence authorization"
>
> <snip/>
>
>>>     Page 27: " As described in [RFC3856
>>>     ], this cancels any notification dialog but
>>>     causes a NOTIFY to be sent to the subscriber, just as a presence
>>>     probe does (the transformation rules for presence notifications have
>>>     been previously described in
>>>     Section 6.2 of this document).”
>>>     A probe would be implemented as a new SUBSCRIBE dialog with expires
>>>     0, which does’t cancel all other dialogs. So while the mechanism is
>>>     the same, using a *new* SUBSCRIBE request with Expires: 0 would just
>>>     be a probe, not a cancellation.
>>
>> I will look into this. What you say sounds plausible but I'd like to
>> double-check it against my reading of RFC 3856.
>
> Yes, that looks right. I would change things as follows (note the new
> Call-ID, too):
>
>    A SIP-to-XMPP gateway would transform the presence probe into its SIP
>    equivalent, which is a SUBSCRIBE request with an Expires header value
>    of zero in a new dialog:
>
>    Example 23: SIP Transformation of XMPP Presence Probe
>
>    |  SUBSCRIBE sip:romeo@example.net SIP/2.0
>    |  Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bKna998sk
>    |  From: <sip:juliet@example.com>;tag=j89d
>    |  Call-ID: 2398B737-566F-4CBB-A21A-1F8EEF7AF423
>    |  Event: presence
>    |  Max-Forwards: 70
>    |  CSeq: 1 SUBSCRIBE
>    |  Contact: <sip:juliet@example.com>;gr=yn0cl4bnw0yr3vym
>    |  Accept: application/pidf+xml
>    |  Expires: 0
>    |  Content-Length: 0
>
>    As described in [RFC3856], this causes a NOTIFY to be sent to the
>    subscriber, just as a presence probe does (the transformation rules
>    for presence notifications have been previously described in
>    Section 6.2 of this document).
>
>>>     General note: the examples with "<show
>>>     xmlns='jabber:client'>away</show>” lack the XML namespace
>>>     declaration for “jabber”.
>>
>> Another good catch.
>
> Actually, 'jabber' is not a prefix here and the namespace name is indeed
> "jabber:client" - this was defined in the very early days of XML
> namespaces and we Jabberites didn't fully understand what a namespace
> name was supposed to look like. :(
>
> If that all looks good, I will publish a revised I-D soon.

A diff is here:

https://github.com/stpeter/sip-xmpp/commit/a3ded08cbf1cc527f3f648813b3ecc46d5039094#diff-7f5e67ec097d24a4490853a1770f411b

Peter