[Sipping] Minutes, SIPPING Working Group, IETF53

["Dean Willis" <[e-mail]>]

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http://www.softarmor.com/sipping/meets/ietf53/notes/minutes.html


Minutes, SIPPING Working Group, IETF 53

Session 1
------------

Chairs announce "Note Well" 2026 provisions. 

Agenda Bash: 
     No Comments 

Status: 
     * SIP-T and ISUP-SIP -- ready to resubmit after blackout 

     * SIP Overlap Dialing -- should be ready for WGLC next month. 

     * Requirements for Deaf -- Hum on objections, none noted, will
     move to last call.

     * E164 and ENUM to discuss in ENUM WG

     * cc-transfer -- depends on refer, replaces, has security concerns 

     * Fax -- new comments from ITU from group review, informal
     liaison reported, formal channels expected to be exercised
     soon. ITU has essentially combined and cleaned up T.38. They want
     to reference this doc, and are happy with it being a a BCP
     instead of informational. They wish to further request
     collaboration and notification of changes. They also suggest
     splitting fax and modem into two separate documents.

     * Call Flows BCP -- needs updates to torture tests, do we need
     some bis-specific torture tests? We also need volunteers for
     formal review on a section-by-section basis, target WGLC for last
     of May.

Service Examples Draft, Alan Johnston: 

     * Updated for bis in this release. 

     * Open issues with getting setup info for transfers, etc. Suggest
     doing the development of the SIP events package proposed in
     draft-rosenberg-sip-call-package.

     * Several issues with Replaces resolved, especially around
     transfer of call. Main one is use of Require: replaces to verify
     capability of foreign node.

     * Join: Some primitive with a function like the
     draft-mahy-join-and-fork "Join" header required to complete
     single-line-extension.

     * Caller Prefs: How should we demonstrate this stuff in call
     flows?

Multiparty Apps Framework Discussion, Rohan Mahy: 

     * The "new" cc-framework is an attempt to bring together
     categories and descriptions and working groups status of various
     drafts across SIP, SIPPING, and individual contributions.

     * Question to group: Is this approach "what we are looking
     for". General response seems favorable, and the document editor
     will proceed.

Conferencing Requirements, Orit Levin and Henning Schulzrinne: 

     draft-levin-sip-for-video: Objectives are a BCP guide for
     building "multimedia" conferencing apps, with similar user
     interface and clear migration path from voice-only connections
     using basic non-extended SIP UAs.

     Stuff in many WGs: * Call control in SIPPING * Capabilities
     exchange/declaration in MMUSIC * T.120 and other app integration
     in MMUSIC * Media control in AVT * Conferencing and Floor Control
     models in SIPPING/SIP

     Media Control is viewed as critical open issue. Where should work
     be done?

     Comment from audience: Sounds like exactly the original charter
     of the MMUSIC working group. Only difference is requirement that
     simple SIP client be able to participate in session. Also
     suggestion that "control channel" is just another media in the
     session, and should be treated as such by the system.

     Comment from audience: The control channel is sort of like but
     not completely like media.

     Suggested approach: do a framework draft, maps requirements to
     solutions using existing drafts andapproaches as possible,
     closely related to multi-party application framework.

     Question from audience: presumes certain boundary around "what a
     conferencing application is", presumably from classic
     conferencing model. What about other approaches, such as
     collaborative editing models?

     Requirements for Conference Control, Henning Schulzrinne: Suggest
     focus on media-independent control for range of conference models
     with core property of single "media choke point". Functional
     taxonomy presented in slides. List of floor control primitives in
     slides.

     Comment from audience: Group membership management is very
     similar to authorization policy for subscription in Events
     structure.

     This problem space seems to have commonalities with SIP:
     asynchronous event functions and synchronous command functions to
     "the conference" (as opposed to commands to participants).

     Work division model proposed in slides. 

     Comments from audience: 

     * Shouldn't split asynchronous events from synchronous commands. 

     * This work spans a lot of groups but isn't in any specific one. 

     * Must make efforts to mesh well across many groups 

     * Missing something in the problem statement: We have not
     addressed of graph building, leaving us with star and mesh,
     neither of which scales. Media transmission along a graph is
     something we're not treating well. Once we can do that, if can
     think about controlling and eventing along the graph. Suggestion
     we decide the problem along these lines.


     -- Response: This is a big effort. With the scoping suggested, we
     have a constituency. Don't want to repeat the last 10 years of
     MMUSIC.

     * Request to get decision on work plan made soon.  Chair
     position: There is clearly interest. We have to work out issues
     of scope and jurisdiction.


Request History Requirements, Mary Barnes: 

     Several examples presented of SIP call diagrams in which there
     may not be enough information in current SIP to make appropriate
     state analyses in various nodes.

     Issues from mailing list discussed in slides. 

     Comments: 

     * the general problem is not one of information loss. Propagating
     information upstream is oen of the problems. The second piece is
     "telling someone why they got a request". this is much more like
     caller pref sand identity issues.

     * need to decide when to throw information away. 

     * may be important problem here, but where? we're getting into
     the identity issue again. We should work on this and try to find
     general problem. there is a profound slippery slope problem.

     * discussion that there is a big difference between the lack of
     information at a random proxy, and the failure of a specific one.

     * It's the systems that manage identities, not the endpoints,
     that need to have knowledge.

     * Need to clearly delineate between "what happened to the
     request" and "what you want the next hop to do".

     Hum for continue working: loud. Open issue with splitting it into
     two pieces.


SIP Telephony Device Requirements, Dan Petrie: 

    tries to formulate requirements for phone-like devices on fixed
    and wireless (not 3G) networks. Includes requirements for device
    configuration.

    Splits issues: 

    1) Configuration discovery -- maybe inside of SIP? 

    2) UA enrollment -- inside of SIP 

    3) Configuration retrieval -- outside of SIP 

    4) Configuration change notification -- may be SIP? 5)
    configuration change upload (phone to server0 -- outside of sip

     Discussion: Use of SIP for configuration discovery and change
     notification. Comment from audience: seems to be a lack of
     understanding and analysis of other protocols for doing
     this. Plea for simplifying the administrator role by reducing
     number of configuration mechanisms. Comment: Didn't we decide not
     to do this two years ago? What has changed? Ans. We have now
     clarified between data transfer (not SIP) and SIP
     identity-related discovery and notification issues. Comment:
     there has been some analysis of SNMP as not adequate. Comment
     from AD: there ARE other conifguration protocols. This would be a
     very hard sell. chair action: defer to list. Hum for in/out of
     scope slightly weighted towards in scope.

Tel: URL enhancement work, Jon Peterson 

     Work is probably moving to iptel group. Please read rfc2806 bis
     and comment ASAP.


Emergency Services discussion, Henning Schulzrinne, Mike Pierce: 

SIP Resource Priority, Henning Schulzrinne: 

     Establish priority when competing for terminating UA
     resources. This is not "network priority", more like an SMTP
     priority flag. Open issue: Do we need an Accept tag?

     Comment: IEPREP group is working on requirements. We should hold
     up priority header until IEPREP has considered more
     requirements. At least we should let IEPREP look at it and see if
     it applies.

     Comment: There are probably privacy and security requirements for
     use of this header needed to prevent SPAM. Security requirements
     in draft are probably not adequate.

     Comment: Needs to be discussion of WHO will be looking at this
     header.

SOS, Henning Schulzrinne: 

     Issue on IANA considerations for reserving names such as
     "SOS@domain".

     Comment: happy to have a BCP saying "SOS is a reserved word" but
     this is not a solution for e911 and we have to be careful that
     this is understood.  Comment: We should use MAYDAY or PANPAN
     instead of SOS.  User Application Control: Bert Culpepper:
     Assumptions and requirements given in slides.

     Open issues: 

     1) What should the mechanism be: Is it SIP? 

     2) IS SIP Events framework appropriate? 

     3) If so, what should payload format be? 

     Comment: If we require people to subscribe, we need to tell them
     WHERE to subscribe Comment: Would like to express higher-level
     semantics than just key scan-codes. For example "jump left three
     feet and shoot" instead of "4,4,4,5" Comment: This is much more
     like a markup problem. Maybe we could provide a standard DTD for
     keys, or perhaps dynamically loaded for custom mappings.
     Comment: Is a stop-and-wait protocol adequate?  Comment:
     Mechanism should be more extensible than just keys, but this is a
     good starting point.  Comment: We don't want to reinvent X or
     VNC.  Comment: Two sets of requirements: delivery, and
     content. These should be dealt with seperately.  Comment:
     Previous questioner asserted difficulty with knowing semantics,
     but a markup approach could solve this.  Comment: There may not
     be a human at the UA, so if you don't have semantic awareness at
     the UA, you prevent useful interaction.  Comment: Current model
     of markup does not solve two-directional question of "what the
     device possesses" as well as the "what are the semantics".
     Chairs: hum for interest? High level of general interested
     indicated. Feed changes in requirements into Bert.


PUBLISH Requirements, Robert Sparks: 

     Covers Donovan's requirements draft. Slides review requirements
     from Donovan draft. Review Stucker draft proposing solution to
     those requirements. Presents discussion of requirements
     abstracted from protocol proposals 1) Binding to SIP identities,
     and 2) Getting the information to the node responsible for the
     application associated with the SIP identity.

     Question: Do we agree we need to meet these requirements?
     Comment: Calling it a "publish" mechanism is semantically leading
     and should be avoided.  Comment: What are the kind of issues that
     would help us decide whether this needs/not to be SIP. Is it a
     single server or a server farm? Does it need to be reliably
     available to more than one place? Comment" this is same as
     REGISTER problem.  Comment: Skeptical if there is such a thing as
     a "generic upload requirement". Generally, this is more like an
     operation against a network object. This is consistent with SOAP
     or RPC.  Comment: We should look at what we know, determine the
     specific requirements, and go from there.  Comment: Whether stuff
     uploaded is merged with an application or used en-bloc is up to
     the application, but a generic mechanism should be doable.


Session 2
-----------

Agenda Bash:
    * No Issues

Accounting/AAA Systems, Bernard Aboba:

    Slides describe requirements of real-world accounting
    requirements, including reliability, security, current issues with
    RADIUS.

    Current issues with RADIUS include:
	- backoff unspecified
	- failover unspecified
	- application layer acknowledgement missing
	- undefined proxy behavior
	- no error messages prevent intelligent failure response
	- transport security has no confidentiality, known attacks
	- replay protection only in post-processing
	- no object security, MITM open

    Alternatives discussed including SNMP, DIAMETER
    
    Question: Why couldn't we use Web Services model and XML over
    secure transport? Answer: accounting semantics are undefined. It
    could be done, but hasn't yet.
    Chair: We had this conversation in order to help us understand
    AAA requirements.
    Question: There are existing systems usually in place
    (RADIUS). Why are we being blocked from working with them?
    Proposal from chairs: Should we be able to do capacity planning
    and non-usage sensitive billing? Consensus yes. Is time sensitive
    billing in scope? Chair's
    Question: We have real requirements -- why are we arguing about
    which grid-box from RFC 2975 we're going to try and fill?
     
    Question: Time-sensitive billing is a requirement from 3G. Whether
    it is interdomain is option. Are we talking about the other two
    A's?
    
    Comment: We should at least consider what has been accomplished with
    a non-IETF protocol in real-world billing systems.
    Question: DIAMETER seems to be the implicit assumption. RADIUS may
    be obsolete, but should we, instead of arguing requirements, just
    do a standards-track spec for using DIAMETER and an informational
    track for using one or more of the existing protocols like RADIUS?
    Allison: There will be resistance to any RADIUS solution on an RFC
    track. Why not just use SNMPv3? Chair comment that that doesn't
    appear to be a good fit for people are doing.
    Question: When will DIAMETER exist? Spec editor reports that major
    issues are done, a few editorial and security considerations
    remain for documentation, otherwise ready to go.
    Observation: RADIUS is widely deployed in accounting for dialup
    internet access. Many providers combine dial=up with VoIP and have
    incentive to use same accounting infrastructure. It would be
    useful for us to document any vulnerabilities of RADIUS that apply
    to SIP that did not apply to dialup. Response: If you're doing
    dialup, you're probably not in usage sensitive billing or at least
    don't have the same requirements as VoIP.
    Comment: It is clear that we are driving while looking in
    rear-view mirror, trying to retrofit VoIP billing on RADIUS. It is
    clear that we have to look at record format (XML), secure
    transport (TLS), and look forward instead of backward.
    Comment: We should keep in mind that we have a lot of work to do
    with things like record transfer and post-processing stuff
    independent of record formats and the like.

Other DCS Drafts:

  draft-scsgroup-sip-proxy-proxy-06.txt:
    Slides report status and background. Need to update for sipchange
    process as ind. informational (P-header, no options tag)

  DCS architecture draft:
    Slides report status. Similar sipchange issues.
    Chairs poll for reading of drafts, and for concerns on informational
    publishing. Comment that we need to know if there are any
intellectual
    property claims, answer "probably".
    Question? Will we apply sipchange? yes.
    Poll for consensus to proceed -- no objections raised.


Report on 3GPP Ad-Hoc from 20Mar02 (Miguel Garcia):
    Path header: current two drafts seem reasonable.
    Privacy: Several problems, no clear resolution yet.
    Dialed URL: (Target Address-of-Record): P-header approach seems
    feasible in the short term, may be able to use history or other
    mechanism in the future. EdNote: This could also be considered
    as something like a "display name" for the request-URI.
    3GPP XML Body: Moving most content to P-headers. 
    Security items as resolved in SIP.

Event Packages Procedure (Rohan Mahy):
    Chairs: Do we need a separate guidelines document for the authors
    of SIP Events?
    Question: Do we have a template that somebody to use to pre-screen
    their work for completeness? ENUM put together a template for
    service field definition. Is the stuff in the sip-events RFC
    adequate? Chairs poll for sufficiency: strong consensus, current
    guidance is adequate.



Call and Conference Package (Jonathan Rosenberg):

    Slides review proposal from drafts and changes including examples,
    bis-alignment, addition of direction attribute, removal of To-
    headers in favor of explicit coding, removal of floor control.
    Next steps: at least one implementation known. Need to make sure
    scope is right and data formats have all information we need. Will
    split document into two packages (dialog and conference). Propose
    adding this effort as SIPPING WG item. 

    Comment: AS we start defining XML event packages, it looks like the
    world has moved on beyond DTD definitions into schema-based
    definitions. We should make a similar evolution in schema
    definition. Chairs: This is reasonable. 
    Comment: This framework is needed for distributed call control and
    the work is supported by the speaker. Several confirming comments
    made. 

    Comment from chair (Rosen): Do we want to do this definition in
    SIPPING or is this something that should be done in SIP? This is a
    "piece" of the problem. It would be really nice to have a bigger
    view. Have we finished the requirements? Response: It's nice to
    understand big picture, but also nice to make incremental
    progress. Chair (Mahy) we need to follow procedure, but we have
    some requirements, can we proceed? Author: It would be nice to
    have some discussion of requirements on data format. This should
    be reflected one-to-one in the result document, so can be done in
    conjunction instead of as a separate effort. This is really a
    "piece of framework". General discussion follows. Poll for
    call-info package, none opposed. Poll for conference info package:
    none opposed.

Future Work (chairs):

    Proposals in slides.

    3PCC BCP: Never an extension because it was doable in straight
    SIP, mostly. This has been greatly improved in bis with o/a and
    update. So the proposed work is to discuss questionable alternatives
and
    recommend best practices from the known alternatives. This is not
    intended to say that 3PCC itself is a better practice than
    distributed. Poll for adoption: no objections.

    Message waiting: Poll for adoption as WG item: no
    objections. Question: package seems to want to do more than voice
    message waiting. Author response: will adjust to workgroup
    consensus. Question: Where do we document interworking this with
    ISDN?

    Content indirection and reason codes: Will continue requirements
    development.

    Opaque URI usage: Proposal to do informational draft on guidelines
    for use of opaque URIs.

    MSURI draft: Propose to either roll into Opaque URI or publish as
    individual informational or do as WG effort. Comment: We haven't
    really as a group figured out how to do this osrt of thing. Would
    like to see something that steps back, looks at broad
    requirements, before delving into solutions. The usage of URIs as
    service indicators is one of the biggest architectural problems
    we face. Counter: This is too large an approach, and we need a
    solution today. Comment: It is important to define a framework for
    discovery. Comment: Unless there is someone pushing to do this
    analysis, the result is likely useless. It is better to proceed by
    just allowing people to document different approaches and label
    them with applicability statements. We don't know how big the
    problem space is, and it is likely to be very large. Comment: we
    need to define a schema. Comment: we need to do requirements, not
    jump into solutions. Comment: we need services, concern that if we
    stall on URI conventions that we'll have problems. Eric Burger
    volunteers to do framework. Comment: Suggest researching
    requirements and publishing msuri as an individual in the
    meantime. Chair comment: would like to see framework or
    requirements first. Poll: SIPPING WG to develop guideline document
    on use of URIs. Result - one opposed.

    SIP VXML: 

    NAT Scenarios Draft: Should we do it as WG efforts? Comment:
    Dealing with NATS is an enormous tar pit. There are many options
    that apply to different scenarios. Discussion on scope
    follows. Comments: it would be good to bidirectionally align this
    with the "unsafe" framework document. Poll: Adopt this as wg item
    leading to informational rfc: None opposed.
    

Emergency Services Discussion (Mike Pierce):

    Slides review status of emergency services draft and relation to
    IEPREP work.  Proposal from chair: Can authors work with authors
    of resource priority header on SIP requirements and move other
    work to ieprep? Answer: That is how the authors are currently
    proceeding.


Open Mic:

    How do we deal with the approval policy for 3PCC stuff like
    accepting REFERs, etc. Ans: should be in usage drafts, if not send
    text.

    Device Requirements: We didn't get to this the other day. Where do
    we stand on it? Comment: There has been some discussion that there
    may be other venues for operational discussions, such as SIP
    forums. Comment: Ideal world would be: IETF realized long ago that
    device configuration is a problem that will be universally faced
    and have developed a "plug-in" framework (like MIBs) for doing
    so. This didn't happen. Comment: discussed taking current config
    document and adding discussion and applicability of things like
    SNMP, ACAP, etc. Comment: The OAM area has committed to reading
    the document and working with the author and other interested
    parties. Comment: This is "right now" problem. We have all the
    tools we need. We need to write down an interop doc. Comment: We
    have a split between framework and content. Can we go forward with
    the definition of the data independent of the delivery mechanism?
    Request from chair: Can we continue this as individual work,
    discussed on SIPPING list, until more clarity?. No
    opposition. Comment: SIP end devices are a whole industry,
    managed by housewives to sysadmins with massive systems. Please
    think about it.

    Settlement: Idea to generate discussion. There might be an
    opportunity to define a generic challenge-response settlement
    architecture framework. Comment: How about a response code that
    says "Payment required -- here's an invoice" something like a
    401/407 challenge, with the re-INVITE to contain payment
    information. Comment: This screams for requirements development in
    the SIPPING process, need to scope the problem, describe some
    scenarios, and send text.

    AAA: Earlier presentation did not explore large solution space now
    available. What we can we do if we bring in web services and
    similar technologies? Consider reviving interdomain settlement/osp
    drafts earlier "out of scoped" in SIP. Chair request: List
    discussion on proposal and approach -- "how can we get something
    done within IETF?" Question: Do you see this work diverging into
    user-service/provider and provider/provider channels? Response:
    Mostly between providers. The important thing is the trust
    function or clearinghouse that enables any-any business
    relationships.


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