Subject: [Stox] Spencer Dawkins' No Objection on draft-ietf-stox-im-12: (with COMMENT)

From: "Spencer Dawkins" <[email-masked]>
Date: Wed, 04 Mar 2015 21:11:19 -0800

Spencer Dawkins has entered the following ballot position for
draft-ietf-stox-im-12: No Objection

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COMMENT:
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I'm glad to see these specifications moving forward. Thanks for that.

I have a couple of you-need-smarter-ADs questions. As prologue, please
remember I have a decent understanding of SIP, an indecent understanding
of SIMPLE, and mostly, I just stare uncomprehendingly when I see raw
XMPP.

It did not jump out at me when reading this specification, whether there
is any assurance to a sender on one side of the gateway that a message
was delivered successfully to a receiver on the other side of the
gateway. If there's not, that might be worth pointing out a bit earlier
than a Note: halfway through page 5.

Is there a possible mismatch between what a sender thinks is happening,
TLS-wise, on one side of the gateway, and what a receiver actually
receives, TLS-wise, on the other side? I'm not smart enough to ask the
right question, but if an XMPP sender knows she's sending over TLS, but
the XMPP-to-SIP gateway maps that into a non-TLS SIP transaction on the
other side, is the kind of scenario I'm thinking of. If so, perhaps it's
worth pointing that out someplace (the Security Considerations section
would be fine).

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From: Peter Saint-Andre - &yet <[email-masked]>
Date: Thu, 05 Mar 2015 09:27:47 -0700

Hi Spencer, thanks for the review. Comments inline.

On 3/4/15 10:11 PM, Spencer Dawkins wrote:
> gateway.

Assurance is a slippery thing. :-)

In XMPP we do have a way to communicate delivery receipts end-to-end 
<http://xmpp.org/extensions/xep-0184.html> but that's an extension to 
the core specs. Given that MSRP has a similar mechanism for session mode 
messaging, we talk about that in draft-ietf-stox-chat instead of 
draft-ietf-stox-im.

> If there's not, that might be worth pointing out a bit earlier

RFC 7247 says:

    As specified in Section 26.4.4 of [RFC3261] and updated by [RFC5630],
    a To header or a Request-URI containing a Session Initiation Protocol
    Secure (SIPS) URI is used to indicate that all hops in a
    communication path need to be protected using TLS.  Because XMPP
    lacks a way to signal that all hops need to be protected, if the To
    header or Request-URI of a SIP message is a SIPS URI then the SIP-to-
    XMPP gateway MUST NOT translate the SIP message into an XMPP stanza
    and MUST NOT route it to the destination XMPP server (there might be
    exceptions to such a policy, such as explicit agreement among two
    operators to enforce per-hop security, but currently they are quite
    rare).

Do you feel that we need to say more here in the IM context?

Peter

-- 
Peter Saint-Andre
https://andyet.com/

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From: Peter Saint-Andre - &yet <[email-masked]>
Date: Thu, 05 Mar 2015 09:27:47 -0700

RFC 7247 says:

Peter

-- 
Peter Saint-Andre
https://andyet.com/

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From: Spencer Dawkins at IETF <[email-masked]>
Date: Thu, 5 Mar 2015 11:28:40 -0600

Hi, Peter,

On Thu, Mar 5, 2015 at 10:27 AM, Peter Saint-Andre - &yet <[email-masked]>
wrote:

> In XMPP we do have a way to communicate delivery receipts end-to-end <
> http://xmpp.org/extensions/xep-0184.html> but that's an extension to the
> core specs. Given that MSRP has a similar mechanism for session mode

I think I understood that. I was just thinking it might be good to say
something like "IMs don't return an indication of success or failure, and
if you need that, you want to use chat instead".

Is that even true? :-)

> Do you feel that we need to say more here in the IM context?

I think that's fine.

Spencer

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From: Spencer Dawkins at IETF <[email-masked]>
Date: Thu, 5 Mar 2015 11:28:40 -0600

Hi, Peter,

Is that even true? :-)

I think that's fine.

Spencer

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From: Peter Saint-Andre - &yet <[email-masked]>
Date: Thu, 05 Mar 2015 10:45:03 -0700

On 3/5/15 10:28 AM, Spencer Dawkins at IETF wrote:
> Hi, Peter,
>
> On Thu, Mar 5, 2015 at 10:27 AM, Peter Saint-Andre - &yet
> <[email-masked] <mailto:[email-masked]>> wrote:
>
>         Please refer to
>         http://www.ietf.org/iesg/__statement/discuss-criteria.__html
>         <http://www.ietf.org/iesg/statement/discuss-criteria.html>
>         http://datatracker.ietf.org/__doc/draft-ietf-stox-im/
>         <http://datatracker.ietf.org/doc/draft-ietf-stox-im/>
>
>
>
>         ------------------------------__------------------------------__----------
>         COMMENT:
>         ------------------------------__------------------------------__----------
>
>     <http://xmpp.org/extensions/__xep-0184.html
>     <http://xmpp.org/extensions/xep-0184.html>> but that's an extension
>     to the core specs. Given that MSRP has a similar mechanism for
>     session mode messaging, we talk about that in draft-ietf-stox-chat
>     instead of draft-ietf-stox-im.
>
>
> something like "IMs don't return an indication of success or failure,
> and if you need that, you want to use chat instead".

That sounds reasonable.

The XMPP method can be used for single instant messages, but as far as I 
understand it there's no similar method for page mode messaging in SIP, 
only session mode messaging in MSRP (so it wouldn't be end-to-end for 
single instant messages).

Peter

-- 
Peter Saint-Andre
https://andyet.com/

---

From: Peter Saint-Andre - &yet <[email-masked]>
Date: Thu, 05 Mar 2015 10:45:03 -0700

That sounds reasonable.

Peter

-- 
Peter Saint-Andre
https://andyet.com/

---

From: Peter Saint-Andre - &yet <[email-masked]>
Date: Thu, 05 Mar 2015 14:54:47 -0700

> single instant messages).

Here is a proposed enhancement to the relevant paragraph in the -im 
document:

    Both XMPP and IM-capable SIP systems enable entities to exchange
    "instant messages".  The term "instant message" usually refers to a
    message sent between two entities for delivery in close to real time
    (rather than a message that is stored and forwarded to the intended
    recipient upon request).  This document covers single messages only
    (sometimes called "page-mode" messaging), since they form the lowest
    common denominator for IM.  Separate documents cover "session-mode"
    instant messaging in the form of one-to-one chat sessions
    [I-D.ietf-stox-chat], as well as multi-party chat sessions
    [I-D.ietf-stox-groupchat].  In particular, session-mode instant
    messaging supports several features that are not part of page-mode
    instant messaging, such as a higher level of assurance regarding end-
    to-end message delivery.

Peter

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From: Peter Saint-Andre - &yet <[email-masked]>
Date: Thu, 05 Mar 2015 14:54:47 -0700

Peter

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From: Spencer Dawkins at IETF <[email-masked]>
Date: Fri, 6 Mar 2015 14:33:28 -0600

Peter,

>    instant messaging, such as a higher level of assurance regarding end-

That's exactly the kind of edit I was hoping for. Thanks!

Spencer

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From: Spencer Dawkins at IETF <[email-masked]>
Date: Fri, 6 Mar 2015 14:33:28 -0600

Peter,

Spencer