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 (iesg(_at_)ietf(_dot_)org) 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 <Gonzalo(_dot_)Camarillo(_at_)ericsson(_dot_)com>
Robert Sparks <rjsparks(_at_)nostrum(_dot_)com>
Real-time Applications and Infrastructure Area Advisor:
Gonzalo Camarillo <Gonzalo(_dot_)Camarillo(_at_)ericsson(_dot_)com>
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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Cullen Jennings
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