Minutes, SIPPING Working Group. IETF 56

edited by Dean Willis

Session 1, Monday March 1700, 1930-2200

Scribe: Vijay Gurbani, Mary Barnes
Chat coordinator: Al with the Hat


Chairs called meeting to order.
Agenda agreed as:

1930 Agenda Bash
1935 Status -- Chairs
Call Control Issues
1945 Service Examples, Alan Johnston
   draft-ietf-sipping-service-examples-04.txt
1955 Call Control -- Transfer, Allan Johnston
   draft-ietf-sipping-cc-transfer-01.txt
2005 Caller Preferences Use cases, Jonathan Rosenberg
   draft-rosenberg-sipping-callerprefs-usecases-00.txt
NAT and Policy Issues
2015 Persistent Connection Management Requirements, Vijay K. Gurbani
   draft-jain-sipping-persistent-conn-reqs-00.txt
   draft-ietf-sipping-connect-reuse-reqs-00.txt
2035 SIP Network Address Translation, Jonathan Rosenberg
   draft-ietf-sipping-nat-scenarios-00.txt
   draft-rosenberg-sipping-ice-00.txt
2045 Session Policy Requiments, Jonathan Rosenberg
   draft-rosenberg-sipping-session-policy-00.txt
2055 URI Leasing, Jonathan Rosenberg
   draft-rosenberg-sipping-lease-00.txt
Design Teams
2105 SIP Conferencing Design Team, Alan Johnston
   Web Page for the Design Team
2135 Application Server Interaction Design Team, Jonathan Rosenberg
   Web Page for the Design Team
2140 Transcoding Design Team, Gonzalo Camarillo
   Web Page for the Design Team
2145 Emergency Calls Design Team, Jon Peterson
   Web Page for the Design Team
2150 Limiting Notifications Rate, Aki Niemi
   draft-niemi-sipping-event-throttle-reqs-01.txt
2200 Wrap


Topic: Service Examples, Alan Johnston

Moving well. Author wishes to add some text discussing how to implement some servcies and discussing trade-offs and expects that draft will be complete before next meeting

Topic: cc-transfer, Alan Johnston

Slides presented, included in proceedings.

This version had few changes: added a section on use of Referred-By header.  Added selected message details.  Added many more call flows on attended transfer and unattended transfer.  Added a security consideration section.  No known open issues with the I-D. Group polled on readiness for WGLC: No objections noted.  Audience asked if there was any overlap or dependency on globally-routable contact URI work. Author belives there is currently no dependency, but that if the GRURI work completes, it would be nice to reference it from this draft.


Topic: Status report: Chairs

Slides presented, included in proceedings.

We have 3 RFCs which have been published, considering the amount of work we had on our plate.  2 on IESG queue; bunch of individual I-D. 3 in here that are ready for WGLC.  A lot of work is blocked on other stuff -- call control, ICE, work going on in midcom, etc.

Note chairs believe that formal expert review is not required for all individual drafts. Current policy is to announce the draft to the list, and ask the participantst to verify that the draft does not conflict with WG efforts. Under the current process, we do a formal expert review for P-headers or when asked to do so by IESG/ADs.

It may be useful for us to split things into smaller groups -- some I-Ds document usage of SIP, others talk about services (cc-conferening, cc-transfer).  It may be appropriate to let some of this work proceed without supervision of the WG.  We may end up doing this in Vienna in order to get up to speed.  Will like to get comments on the mailing list or after session on if this is okay.



Topic: Caller-Preferences Use Cases, Jonathan Rosenberg

Slides presented, included in proceedings.


Poll: Useful, interest in accepting as WG document? Strong consensus recorded. AD suggested that these use cases be packaged with CallerPrefs drafts.



Topic: ICE, Jonathan Rosenberg

Slides presented, included in proceedings.

Provides general methodology for using address-fixing protocols to get SIP through NAT.

Question: What is the impact if some sort of underlying mobility function causes node address changes? Does ICE resolve? Ans: Unknown, but we think it should work if the frequency of address changes is lower than 1/RTT.

Question: Does having STUN server on every node open up the network to denial-of-service attacks on NAT translation? Ans: No -- at least, no more than port-scanning already would.

Poll: Who read: fairly large number.

Question: Muxing STUN and media -- is that required? What is the implication of demux? Ans: It seems to be feasible to use magic-cookies in the TUN level to work it out.

Comment: This DOES require widespread deployment to be useful, can we get that? Ans: If it works, people will implement it.

Question: What are implications if only one end supports?  Ans: We fall back to what we have now. Question: IS it easier to fix the NAT than to fix the SIP? Ans. Debatable.  There's a lot of $39 NAT boxes out there.

Poll: How many people would be interested in implementing? (several) Will one volunteer to write the preconditions (document things like like SDP changes, requirements in SIPPING) Yes-- Cullen Jennings.

Poll: Would you like this work to be documented in SIPPING, along with fallback to previous modes? Ans: Loud response, a few dissenters. Proposal: Cullen to work on preconditions, Jonathan to work on furthering ICE draft, WG to request authorization to pursue as WG effort.



Topic: Session Policy Requirements, Jonathan Rosenberg

Slides presented, included in proceedings.

Slides presented reviewed scenarios. Poll: Do we want to work on this? Brian Rosen reports that he really needs this for dealing with 6Mb/s streams and managing admissions policy dynamically. Another comment made that this approach could obviate the need for some B2BUAs. Comment that we should add requirements to do this without "new headers" and it shoud work with e2e encryption (req #1 in presentation). Poll: who thinks we should take this work on as a baseline for requirements? Strong consensus reported, none opposed.

What happens when a service provider wants to insist on some aspects of a session (media flows through a realy, video not be used, etc.) So far this has been done with SDP modification.  Well known problems: does not work with data encryption, requires proxies to have knowledge of session descriptions, proxy complexity increases, ...

Solution: 3GPP does this -- they use 488 as a response code to list codecs which are acceptable.  This has some drawbacks as well.

Do we want to work on this problem?  That is the real issue for us to decide now.

Many people approached the mic and agreed to the requirements being valid.

Keith Drage suggested that we resolve the requirements before proceeding with a solution, and that consideration of various solutions (such as Jonathan's proposal) should be deferred until the requirements are agreed.

Poll: who thinks we should take this work on as a baseline for requirements? Strong consensus reported, none opposed.  Chairs will  request approval as a WG item from ADs.




Topic: URI Leasing, Jonathan Rosenberg

Slides presented, included in proceedings.

Material introduced from slides.

Question: This allows for temporally scoped URIs. Can we give an example of where this would be useful? Ans. Assume a conference call running over a set time. Discussion that current document may be a bit complex in this area. The word "temporal" is probably misapplied in this context and the author would like to withdraw it. This all comes down to embedded route headers vs. a lease-and-preference model. Perhaps we need to step up a level and ask what the top-level requirements really are? The draft proposes three explicit. There may be also "without hiding state in the domain name" and some others.

Comment: Leasing seems to imply temporal scoping. Huh? Long discussion . . .

Comment: It seems that all of the given requirements could be met by relaxing a single restriction in 3261. 

Conclusion: More list discussion on requirements needed.



Topic: App Interaction Design Team, Jonathan Rosenberg

Slides presented, included in proceedings.

Minimal activity since last meeting. We should develop use cases illustrating the requirements. Jonathan Rosenberg requested that proposed use cases be sent to him via email.



Topic: Persistent Connections, Vijay Gurbani

Slides presented included in proceedings.

Basics presented. Discussion ensued.

Question: What is the requirement difference between signaled persistence and simply configuring persistence?

Assertion: Reuse is only important in the client-server case.

Assertion: This sounds like my kids discussing bedtime. There is really only reason to close a TCP connection -- to recover resources. Therefore, the interesting thing, is not how do connections come up, but figuring out which connection to kill if we need to kill one.

Assertion: the mechanism here is equivalent to "just doing the right thing" with TCP, so we should fix it operationally, not by changing the protocol.

Poll:  Should we change the SIP spec to encourage leaving TCP connections open unless they need to be closed? Strong consensus reported. Proposed that we do minimal bug fixes in SIP, and do a separate document with an operational focus on "how to" reuse TCP, initially as a discussion and possibly leading into a BCP. No objections noted. Vijay Gurbani may volunteer to lead on a usage document.



Topic: Conferencing Design Team, Alan Johnstson

Requirements, Framework, and Call Control ready for WG adoption. Conference Policy is splitting into two and should be ready shortly. Media policies work requirements progressing, work on policy manipulation is ongoing, and the policy work needs a new home. MMUSIC is not going to adopt this in their new charter.

Question: This policy work is related to data manipulation in SIMPLE, can we combine it? Ans: Probably not. One is data manipulation, the other is policy RPC.

Open issues recapped in slides.

Discussion of absolute vs. relative time in focus. Why not have absolute time? Ans. Simplifies timeing coordination on focus.

Comment: We do have requirements for realtime transitional controls for things like camera-follows-speaker. SOAP and ACAP don't combine to meet this requirement. Ans: This is for more persistent policy, not floor-control. Floor-control remains a media problem.

Poll: Do we wish to, as proposed, adopt the requirements, framework, and call control drafts as wg efforts? Strong consensus, no objections.

Question: Is discovery in-scope? It could be a furball.

Request: Make focus migration happen sooner rather than later. This will be required for three-way to more-way migrations. This is also important from a fault recovery standpoint. The call-control is easy, just a REFER series, but handling the policy migration is more interesting.

Discussion: Policy group needs working group home.  Rohan: mmusic will NOT be chartered to do this; so it is either us or a new BOF.  Will work it out with the ADs later.  We have not been told that we have to stop working on this.

Open issues: conference policy protocol, floor control, notifications.

Proposed: Adopt Reqs, framework, and call control I-Ds as WG documents.  Poll taken, and strong consensus reported.

Open reqs: discovery, focus role migration, cascading and camera control.



Topic: Hearing impaired media transcoding, Gonzalo Camarillo

Work proceeding, no surprises.  Author reports little  progresssince last IETF and  believes that now that we have media policy I-D and session policy reqs, we will make more progress for the next IETF.



Topic: Emergency calling design team, Jon Peterson

Work proceeding, will try to have face-to-face meeting here. Two cases -- regular 911 calls, and PSAP access-link replacement. Can we divide these two cases so that there is something available for "today's PSTN PSAP"?



Topic:  Event Throttling Requirements, Aki Niemi

Notification rate limiting is the "common factor" among most of the event filtering discussions. Issues: Is the model accurate and appropriate? Do we need both the leaky bucket and the strict throttle? Is it ok to leave handling of quarantined notifications out of scope? Is this work useful?

Discussion: It may be important to have a different throttling mechanism for "aggregated/filtered" notifications than for simply prioritized or decimated notifications. The current work does not really consider notification volume/size, just counts. Discussion about the difference between quarantine and gating/throttling functions. One can define a five-token multibucket scenario that's fairly complete. Is this too complicated to be practical? Volutneers to review reqs -- Jonathan, David Oran, and Tomn Taylor volunttered. Poll for adoption: none opposed. Question: Is there standardization required to be able to rate limit?

Event Throttle Requirements, Aki Niemi

Aki went through the model and the requirements (see slides). Issues: Is the model accurate and appropriate? Do we need both leaky-bucket and the strict throttle models, or is only one of them enough?

Observation from floor: Quarantining and throttling are not the same thing. One introduces delay the other control rates.

Rohan: Jonathan, Dave Oran and Dean will review the I-D and the  WG will receive an update from them before this becomes a WG document.


 


Session 2, Wednesday March 19, 1530-1730:

Scribes: Paul Kyzivat, Vijay Gurbani
Chat coordinator: Brian Rosen

Session called to-order by chairs. Agenda agreed as follows:

1530 Agenda Bash
Security Related Issues
1535 Role-based Authorization Requirements, Jon Peterson
   draft-peterson-sipping-role-authz-00.txt
1545 Request History, Mary Barnes
   draft-ietf-sipping-req-history-02.txt
   draft-barnes-sipping-history-info-02.txt
Operations
1605 SIP Endpoint Service Charging Requirements, Wolfgang Beck
   draft-beck-sipping-svc-charging-req-01.txt
1615 SIP User Agent Configuration - Dan Petrie
   draft-ietf-sipping-config-framework-00.txt
1625 Issues in Dual Stack Environments, Hakan Persson
   draft-persson-sipping-sip-issues-dual-stack-00.txt
1635 SIP-AAA Requirements, Gonzalo Camarillo
   draft-ietf-sipping-aaa-req-02.txt
Media Related Issues
1645 Early Media, Gonzalo Camarillo
   draft-camarillo-sipping-early-media-01.txt
1710 Network Announcements, Eric Burger
   draft-burger-sipping-netann-05.txt
1720 Considerations on the IPREP Requirements, Jon Peterson
   draft-peterson-sipping-ieprep-00.txt
1730 Wrap



Topic: Role-Based Authentication, Jon Peterson

Slides introduce concept. Question: Can you show some use cases? Assume two previously unassociated carriers in a federation wish to exchange calls. One carrier issues an authorization object, which the caller hands to the other carrier, allowing the call to proceed. Other examples followed. 

Discussion from floor:  Are we proposing replacing identity with  roles?  Jon responded that this could encompass identity, but maybe not.  suggested from floor that we add more in doc explaining relationship between identity and roles, agreed to by author.

Request: Somebody asked for more use cases. Was also concerned whether all stated  requirements were self consistent.

Observation from floor: Jiri Kuthan suggested that this was a replacement/alternative for  network asserted identity.

Observation from floor:  Somebody suggested that Role wasn’t exactly the right term to use.



Topic: Request History Rqmts and Solution, Mary Barnes

Slides presented, included in proceedings. Mary Barnes presented current status of both documents. Both  requirements and solution have had two new versions since last meeting,  now up to -02. Mary explained changes. Of note - separating out security  requirements, to separate document.

Remaining open issue is security, which is work-in-progress, which a seperate security solution draft expected soon.

Consensus that requirements document is roughly complete and should be referred to SIP WG for action. Chairs need to refer to AD for approval.



Topic: SIP Endpoint Service Charging Requirements, Wolfgang Beck

Slides presented included in proceedings.

Introduces requirements and a model for third-party trust assignment with SIP. Possibly combinable with role-based-authorization.

Proposal: this should be two drafts, one around charging and another about advice-of-charge.

Comment: this seems to be limited to a fixedSIP architecture as currently written.

Comment:  the evaluation of the requirements presented in the draft would be greatly aided by the inclusion of use cases.

Comment: reading the document indicates a specific business model in-mind. Work here should be network agnostic and not make assumptions about who is paying (like caller always pays) etc.

Question from chairs: Are we interested in trying to gather requirements to support an endpoint based charging model (i.e., not billing from intermediaries). Consensus that we would like to see the work more completely illustrated, including use cases, before considering its utility.



Topic: Config Framework, Dan Petrie

Slides presented included in proceedings.

Open Question: Should HTTPS be a SHOULD or MUST strength reequirement: Ans. MUST implement, SHOULD use. Open Question: Is HTTPish preferred to LDAP or ACAP?
Open Question: Is this related to NETCONF work?

Discussion: There are issues here that cannot be fixed with HTTPS pixie dust. You need a separate mechanism of top of HTTPS to verify the identity of the node requesting configuration. Of course, this needs to be configured in. So there is a bootstrapping problem.

Open question: device identity parameters: User-agent header? New header? No decision made.

Open question: How to indicate profile type? Accept-header or event header parameter or request-URI? Comment: this is the same problem as SIMPLE's buddy list management and should use the same mechanism. Further discussion taken to the list.

Dan Petrie presented. Identified changes from prior version.
(draft-petrie-sipping-config-framework-00)

There were comments about strength of use for HTTPS for content indirection in here. General sentiment seemed to be that HTTPS should be MUST implement, SHOULD use. Other protocols other than http/https are  also possible.

Henning Schulzrinne said https isn’t enough. Said there were both confidentiality issues as well as way to ensure the client gets the right data. In absence of client cert, which you can’t assume during  config, presents difficult problems – how to bootstrap.

Dan acknowledged this problem, and said he has already proposed to do  work to deal with that. Further discussion went on. Rohan asked that
this go to list.

Dan requested input on list for where device identification should go – in User-Agent header or somewhere else.

Discussion of profile type – where to indicate in subscription. Jonathan Rosenberg thought you could subscribe to a different request uri for each kind of thing. Rohan Mahy disagreed. Was sent to the list for discussion.

Jonathan suggested this is similar to SIMPLE problem regarding buddylists, and the two works should be synchronized.



Topic: Dual-Stack Issues, Hakan Persson

Slides introduce problem and recaps several solutions. The "contact" problem seems to be addressable in part by dual-interfaced record-route and in part by ICE. The document will be revisited by the author exlporing usage of these techniques and, if the solution is satisfactory, can become a usage document illustrating the solution to the problems it has already raised.



Topic: AAA Req, Gonzalo Camarillo

Slides presented included in proceedings.

Currently in WGLC. Poll: Any issues that have been missed? No new issues. Attendees encouraged to follw WGLC.



Topic: Early Media, Gonzalo Camarillo

Slides presented included in proceedings.

Open issues: There appear to be three ringback states from ISUP, and only two codes (180, 183) available in SIP. Not all protagonists are present and the author proposes to hold a conference call for resolution. Debate ensued anyhow, trying to capture essence of the issue. Francois, Flemming, Rohan,  others agreed to send use cases illustrating the issues they need solved. Poll: should we add a flag? No clear consensus



Topic: Network Announcements, Eric Burger

Slides presented included in proceedings.

Open Issue: Media on Hold? What does a media server do when it gets put on hold? This seems to be application specific, not a SIP protocol problem.

Open Issue: 409 Result code proposal? Suggestion from audience Can we TRY not to use things that are used in HTTP to mean something different? Sugggestion: Could we use a standard response code and a Reason field? Conversation deferred to list with emphasis on 6xx vs 4xx debate.

Open Issue: Multiple Media Streams:?  What do do then, to play multiple things? Eric asserted this isn’t an issue if the target uri is a composite object. He wanted to know if that is the predominant use case. And if not, how would the multiple streams be synced? Brian Rosen wondered why it isn’t good enough to pick one stream. Confusion reigns, deferred to list.

Open issue: IS everything in this draft consistent with WG usage? We need to be sure we're aligned with conferencing and early media work? Author asked to work with Alan Johnston on conferencing alignment, and Gonzalo Camarillo on early media.



Topic: IEPREP Considerations, Jon Peterson

SIPPING asked to provide formal response to the IEPREP considerations, widely discussed on mailing list. Open Issue: SHOULD we address this here? As there is already work in SIP on the priority header? Should we do it here?

Discussion:

Jon Peterson presented. Said this work was in response to requests by  area directors for comments on RFC3478. This is Jon’s private attempt at comments, based on some discussion on list.

Jon raised privacy issues. Henning said there are fundamental tradeoffs between privacy and proxies, and that therefore it is necessary to offer endpoint with options for either.

Keith Drage asserted that either there is an error in the IEPREP requirements that ought to be fixed there, or else it should be dealt with by SIP in responding to the requirements, so there is no need for SIPPING draft in this instance. Allison Mankin agreed, said the area directors could deal with this aspect now, and don’t  need any more input.

Rohan observed that SIP already adopted a mechanism that relates to this. :

Meeting concluded.