Re: WG Review: Call Control UUI for SIP (cuss)

[Alan Johnston <[e-mail]>]

Cullen,

Your characterization of this charter is inaccurate.  It is not about
transporting proprietary information in SIP but rather standardizing an
approach for applications to utilize SIP without having to have another 1000
SIP extensions and RFCs for every application that uses SIP.

Instead, it is about defining a standard mechanism so that *applications*
can transport information orthogonal to SIP in call control messages.  In
the past, we have had this conceit in SIP that SIP is the center of the
universe and needs to understand everything above and below it in the
protocol stack.  We have violated layering so many times and in so many
ways.  This mechanism is a first step towards rectifying this.  So if you
believe that SIP as a protocol needs to understand every piece of
information and every aspect of the applications that use it, I'm going to
argue with you.

Now we have one extremely well deployed and used application used in
enterprise communication today - the ISDN User to User Information service.
If we can't support this simple service in SIP - the idea that an
application can transport information opaque to the signaling protocol -
then we have failed as a standards body.  I don't want this to happen, and
enterprise users of SIP do not want this.

Now, is this ISDN User to User Information service the best way for an
application to use SIP?  Absolutely not!  The ISDN service requires
provisioning on both sides so that they correctly interpret and understand
the UUI.  And you have to take special care not to mix UUI between
applications.  That is why this working group is not just about the ISDN
service - that wouldn't be very interesting.  Instead, this charter is about
defining that application and allowing for new ones to be created.

New ones will need to write their own specs and define what their UUI is,
how it is encoded, etc.  This will clearly promote interoperability.  It
will be easy to transition current users of the ISDN User to User service to
this better service that takes advantage of the Internet and SIP fully.

Now the final piece of the puzzle is the discovery and negotiation piece.
This is totally absent in the ISDN service.  Once we see the other
applications, we will be able to design an appropriate discovery and
negotiation mechanism.

So hopefully we are agreed that this is where we want to end up with this
mechanism.  But we can't get there from here - we need to provide basic
support for the ISDN service first, then the ability to transition away from
it.  And doing it for one little application at a time, having to charter a
new working group for each one clearly would be a waste of everyone's time
and resources.

Many of us have worked hard on this approach over many years, and you have
been involved in this at every step of the way, in both SIPPING and
DISPATCH.  For you to just try to block even the formation of a working
group to address this at this eleventh hour is just not right.

Thanks,
Alan


-------- Original Message --------
> Subject: Re: WG Review: Call Control UUI for SIP (cuss)
> Date: Mon, 28 Jun 2010 20:24:23 +0200
> From: Cullen Jennings <[e-mail]>
> To: [e-mail] <[e-mail]>
> CC: IETF Discussion Mailing List <[e-mail]>
>
>
> As far as I can tell, the WG says they wants to transfer some
> information to achieve cross vendor interoperability. However, what I
> believe the charter is actually going to do is exactly the opposite of
> that. When you get your head around what this charter is proposing, it
> is going to form a more or less opaque container for transporting
> proprietary information in a SIP header. It's hard to imagine how this
> will help interoperability.
>
> If we wanted to have interoperability, the charter would say what
> information needs to be transferred and have the WG define a way to get
> it between systems in an operable way. What the charter for this WG
> actually says they are going to do is make a special container for
> transfer proprietary information.  There's not even willing to say what
> that proprietary information is used for other than things ISDN UUI
> which is a  non interoperable and fairly proprietary field in ISDN.
> Furthermore they have asserted that  existing containers such as SIP-T
> or SIP bodies can't be used for reasons that are hard to describe. (I
> reject the idea that because the call might not involved the PSTN, it
> can't use SIP-T).
>
> I think the folks that want to do this should get a much clear
> explanation of how this results in interoperability and why exist
> approach such as SIP-T will not work before this is chartered.
>
> I do think there is a need to standardize some important call control
> information used in call centers and related places. However, the "we
> need a standard container to exchange secret information WG" is a bad
> idea and violates the sprit of the SIP change process not to mention the
> mission of the IETF.
>
> In summary, I'm in favor of figuring out what the problems are people
> hope to solve with this WG and figuring out a way to write interoperable
> standards to achieve that. However, I think this charter should be
> rejected by the IESG and sent back to the drawing board. The RAI area
> has things of higher priority items to work on than a SIP header for
> transfer proprietary data.
>
>
>
> On Jun 22, 2010, at 10:00 , IESG Secretary wrote:
>
> > A new IETF working group has been proposed in the Real-time Applications
> > and Infrastructure Area.  The IESG has not made any determination as yet.
> > The following draft charter was submitted, and is provided for
> > informational purposes only. Please send your comments to the IESG
> mailing
> > list ([e-mail]) by Tuesday, June 29, 2010.
> >
> > Call Control UUI for SIP  (cuss)
> > --------------------------------------------------
> > Current Status: Proposed Working Group
> >
> > Last modified: 2010-06-21
> >
> > Chair(s):
> >  TBD
> >
> > Real-time Applications and Infrastructure Area Director(s):
> >  Gonzalo Camarillo <[e-mail]>
> >  Robert Sparks <[e-mail]>
> >
> > Real-time Applications and Infrastructure Area Advisor:
> >  Gonzalo Camarillo <[e-mail]>
> >
> > Mailing Lists: TBD
> >
> > Description of Working Group:
> >
> > The Call Control UUI for SIP (CUSS) working group is chartered to
> > define a Session Initiation Protocol (SIP) mechanism for transporting
> > call-control related user-to-user information (UUI) between User
> > Agents.
> >
> > The mechanism developed in this working group is applicable in the
> > following situations:
> >
> > 1. The information is generated and consumed by an application using
> >   SIP during session setup but the application is not necessarily
> >   even SIP aware.
> > 2. The behavior of SIP entities that support it is not significantly
> >   changed (as discussed in Section 4 of RFC 5727).
> > 3. Generally only the User Agent Client (UAC) and User Agent Server
> >   (UAS) are interested in the information.
> > 4. The information is expected to survive retargeting, redirection,
> >   and transfers.
> > 5. SIP elements may need to apply policy about passing and screening
> >   the information.
> > 6. Multi-vendor interoperability is important.
> >
> > This mechanism is not applicable in the following situations:
> >
> > 1. The behavior of SIP entities that support it is significantly
> >   changed (as discussed in Section 4 of RFC 5727).
> > 2. The information is generated and consumed at the SIP layer by SIP
> >   elements.
> > 3. SIP elements besides the UAC and UAS might be interested in
> >   consuming (beyond applying policy) the information.
> > 4. There are specific privacy issues involved with the information
> >   being transported (e.g., geolocation or emergency-related
> >   information).
> >
> > User data of the mechanism will be clearly marked with the
> > application, encoding, semantics, and content type, allowing policy to
> > be applied by UAs.  The working group will define the information that
> > each application must specify to utilize the mechanism. This type of
> > application-specific information will be specified in standards-track
> > documents.
> >
> > One important application of this mechanism is interworking with the
> > ISDN User to User Information Service.  This application defined by
> > ITU-T Q.931 is extensively deployed in the PSTN today supporting such
> > applications as contact centers, call centers, and automatic call
> > distributors (ACDs).  A major barrier to the movement of these
> > applications to SIP is the lack of a standard mechanism to transport
> > this information in SIP.  For interworking with ISDN, minimal
> > information about the content of the UUI is available to the PSTN-SIP
> > gateways.  In this case only, the content will just indicate ISDN UUI
> > Service 1 interworking rather than the actual content.
> >
> > Call control UUI is user information conveyed between user agents
> > during call control operations.  As a result, the information must be
> > conveyed with the INVITE transaction, and must survive proxy
> > retargeting, redirection, and transfers.  The mechanism must utilize a
> > minimum of SIP extensions since it will need to be supported by many
> > simple SIP user agents such as PSTN gateways.  The mechanism must
> > interwork with the existing ISDN service but should also be extensible
> > for use by other applications and non-ISDN protocols.
> >
> > Even though interworking with the PSTN is an important requirement,
> > call control UUI can be exchanged between native SIP clients that do
> > not have any ISUP support. Therefore, existing SIP-T
> > encapsulation-based approaches defined in RFC3372 do not meet the
> > requirements to transport this type of information.
> >
> > Mechanisms based on the SIP INFO method, RFC2976, will not be
> > considered by the working group since the UUI contents carry
> > information that must be conveyed during session setup at the user
> > agent - the information must be conveyed with the INVITE transaction.
> > The information must be passed with the session setup request
> > (INVITE), responses to that INVITE, or session termination requests.
> > As a result, it is not possible to use INFO in these cases.
> >
> > The group will produce:
> >
> > - A problem statement and requirements document for implementing a SIP
> > call control UUI mechanism
> >
> > - A specification of the SIP extension to best meet those requirements.
> >
> > Goals and Milestones
> > ====================
> >
> > Sep 10 - Problem statement and requirements document to IESG
> > (Informational)
> > Mar 11 - SIP call control UUI specification to IESG (PS)
> > _______________________________________________
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> > [e-mail]
> > https://www.ietf.org/mailman/listinfo/ietf-announce
>
>
> Cullen Jennings
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