Subject: [sip-overload] minutes from SoC Interim Meeting II (December 1st)

From: Salvatore Loreto <[email-masked]>
Date: Wed, 8 Dec 2010 17:11:22 +0200

Hi there,

below the notes from the SoC Virtual interim

Please review them and submit any correction to the chairs by Wednesday, December 15th.
The chairs will send the notes to [email-masked] by Friday, December 17th.

(many thanks to Vijay Gurgani and Keith Drage for taking notes during
the meeting)

cheers
/Sal

SIP Overload Control (SOC) Virtual Interim II
Wed-Dec-1-2010 10:00a US Central

Sal, chair slides
No f2f meeting in Beijing, hence the virtual interim.
Plus, work was not progressing as fast as we'd like.  Hence the
virtual interim.

Agenda bashed.  No changes.

Chairs would encourage people in WG to participate to move
it forward.

Considering one more interim in Jan/Feb to speed up the work.

Will have an official f2f meeting @ IETF-80.

Behind the first milestone (Sep 2010 for design considerations.)

Dec 2010 was the deadline for sending overload control mechanism
to IESG.  Will not meet the deadline.

May 2011 is the third document (SIP load filtering mechanism)
deadline.

RjS: Send in a request to update the dates.
Volker: Will like to wrap up the milestones ASAP.  Even if we
move them out, that is not the default mode of operation.

Volker, Overload design
-----------------------
WGLC done and -02 released.  Received lots of comments for
-02.  Janet did a detailed review.

Discussion item: What happens if SIP server is overloaded for
other reasons than processing SIP messages (updating database,
etc.)  In this case, the server WILL apply overload control
mechanisms.

OC mechanism in each direction (A->B, B->A) to be considered
separately.

Added text to handle the case of load balancing and server farms.
Vijay: How D,E,F communicate (on slide 5) to determine server
farm overload value is out of scope.
Volker: Yes.

Janet: Computational complexity is whether it is NP-complete,
change to "computational load" instead of "complexity". (slide 6)

Volker: I will make final small changes and submit for WGLC.

Sal: Want to do WGLC before Christmas vacation and hand to
IESG during Christmas.

Keith: Do you need all 14 days for 2nd WGLC?  No one is raising
any new issues.
Volker: We can get it below 14 days if everyone agrees.
Janet: 7 days is okay with me.

Vijay, Overload control
-----------------------
Draft background.

Covers current status.

Open issue #1

Has had list discussion.

Proposal floated on mailing list to add 4th optional parameter called "oc-algo"

Question from Vijay: Do we need to involve IANA.

Volker: Thinks that the mechanism should be kept as simple as possible and having a default helps make things simple.
Could specify the extension algorithm in this draft or specify them in other drafts.

Vijay: Did not forsee producing another draft containing another parameter.

Janet?: Need to avoid negotiation mechanism.

Volker: In messages would get feedback.

Vijay: After further thought, thinks out of band mechanism is not valid.

Charles: How to define extension? How does it plug into this document? Second questions is the extension itself.

Keith: Cover general protocol compatibility as well. How does any extension to the proposed protocol get handled.
What are the extension mechanisms?

Vijay: Not currently covered in -0.

Janet: Do need to understand the grammar.

Vijay: Think what we are intending at the moment is good, i.e. this is the class of algorithm that we are trying to specify.

Vijay: Downside of not doing this is have to have an RFC that defines those algorithms. [Meant specification required]

Summary: oc alg parameter optional. Other drafts that come up with new algorithms will need IANA registration.

Open issue #1a:

Janet: Addressed in design doc. Has text on 100 trying already.

Vijay: Optional.

Queries on what this means.

Janet: Pointed to previous overload scenarios in other protocols.

Vijay and Volker both support "SHOULD" use.

Keith pointed out that it had to have the condition "use only if confident that under conditions of overload, you do not break the retransmission quenching".

Open issue #1b:

Janet: Negotiation in advance works fine, but during operation no.

Volker: Should not change from one message to the next. Don't need negotiation at beginning, pick one and stick with it.

Robert: Do we want to preclude the case that the server will not want to change the algorithm.

Janet: Or even something more dynamic. Start using loss based, but then change based on conditions of rapidly varying load because loss is not working.

Volker: Worry about switching algorithms rapidly because most algorithms measure over a period, and this will be disrupted by frequent changes.

Eric: Question.

Jannet: Answer already covered.

Vijay: WHat we are talking about here is renegotiating.

Summary: Should not preclude renegotiation, but identify the issues with doing it. Should not modify on a per transaction basis.

[Discussion about what we actually meant by selecting new algorithms and results]

Vijay: Not possible to fine tune so change every transaction.

Open issue #2

Attended to in the design document. No mention of load balancer in the control document.

Proposal, add nothing more than a reference, if anything at all.

Next steps.

Janet: In 4.2. 5th para, text refers to retransmitting a response. When would a response get retransmitted.

Clarification provided from Robert.

Janet: Make sure all requirements of 5390 are met.

Keith: Record as appendix in document, and then decide at end of process whether to keep or remove.

Vijay: OK.

Charles Shen, filter
---------------------

Went through the slides and modifications from last section.

Janet: We went through an extensive discussion before on RPH.
Just take the text and put it in here.

Keith: What are the conformance requirements for RPH?  lower
case "should" and not upper case (slide 4).

Charles: They are discussed in more details in other documents.

Keith: Insert a note that to refer to other documents (design
and control).

Volker: Any reason to make rate the default here?  Can we make
it loss like it is in overload-control?

Charles: Discussions seem to indicate that in this situation,
rate-based is better.

<Discussion between Charles and Volker ensued where it was
decided that because of different requirements between overload-
control and this draft, rate-based as the default seems
appropriate here.>

Open issue (slide 7): Mandatory default schema.  The draft does
not preclude other schemas to be used (ETSI schema, for example.)
If that schema is used, then the default schema will not be
used, but the doc mandates the default schema for interop.
Three solutions in slide 8.
Charles: Do we need to specify a mandatory schema for interop?
Keith: Take the discussion to the list since people on the virtual may not be familiar with the intricacies.

Open issue: Should this be adopted as the WG item as a deliverable
towards the third charte?

Sal: We need a WG item for this, and this is the only proposal we
have.  We cannot take the decision here, need to take it to the
list and issue a call for adoption.

Janet: Before it can be adopted we should ensure it meets all
the reqs of rfc5390.  It seems to work for the case where there
is a finite set of upstream elements, but may not meet req-10.
we should categorize which reqs it meets or which it does not.

Volker: The use case for this is slightly different and may not be
covered in the reqs document -- this draft talks about when you know
that you will be in overload control in advance.  Reqs document
talks about when you DO NOT know that you will be in overload in
advance.

<Discussion ensued on making sure this document explains why
this document does not meet rfc5380 and document this.>

There was one more agenda item to cover, but meeting ran out of
time and was adjourned at 11:33a US Central.  Spillover to be
discussed in the next interim.

or not