Notes, SIPPING WG, Session 1, ietf 53

Recorded and edited by Dean Willis

Chairs announce "Note Well" 2026 provisions.

Agenda Bash:

No Comments

Status:

* SIP-T and ISUO-SIP -- ready to resubmit after blackout

* SIP Overlap Dialing -- shjould 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 liason 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 seperate 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 frmwawork draft, maps requirements to solutions using existing drafts andapproaches as possible, slosely related to multi-party application framework.

Question from audience: presumes certain boundary around "what a conferencing application is", presumably from classic conferncing 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 asnychronous 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 contolling 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 Rerquirements, 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 differendce between the lack of information at a random proxy, and the failure of a

* 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 spllitting 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 conifguration.

Splits issues:

1) Configuration discovery -- maybe inside of SIP? 2) UA enrollment -- inside of SIP 3) Confiuration retreival -- outside of SIP 4) Configuration change notification -- may be SIP? 5) conifguration 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 carefult 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 suscribe, 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 stanadard DTD for keys, or perhaps dynamically loaded for custom mappings.

Comment: Is a stop-and-wait protcol 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 twoi-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 orused en-bloc is up to the application, but a generic mechanism should be doable.

updated  19 Mar 2002 02:10 PM -0600