Subject: [ppsp] Notes from PPSP Bar BOF

From: James Seng <[email-masked]>
Date: Wed, 25 Mar 2009 01:26:17 +0800

Summary by James Seng

* Still have uncertainties of the goal of PPSP, suggest working on an
architecture document covering different components and analyze each
components wrt to the work done or current being work upon by other WG
in IETF

* Rough consensus in the room that the PPSP should "narrow" its scope

* Rough consensus in the room to proceed with a proper BOF at the next IETF

ps: Who has the attendance sheet that was circulating around?

---
Notes taken by Christian Schmidt

P2P for Streaming Protocols
2nd BarBof IETF74 San Francisco

Mo 23.3.2009, 20:10-22:00

Chair:
Zhangyunfei, China Mobile
James Seng, PPLive

Minutes:

Christian Schmidt, Nokia Siemens Networks

Participants:

(about 40 interested people in IETF73 Mineapolis)
(about 40 interested persons in IETF74 San Francisco as well).

Gonzalo Camarillo as IAB member in the room. (Lars Egers could not take part).

Problem :

Interoperability Problem

* Christer Homberg: Do this provider want to switch to a standardized mechanism?
* James Seng: These companies plan to change this. Technology is not
the key differentiator, it’s the different contents they provide.
* Rony Even: It’s a combination of service provider and equipment
vendor who drive this standardization.
* Henning Schulzrinne: All vendors had proprietary versions in the
beginning. Smaller companies have no changes to use them, e.g. due to
legal reasons.

What the concept of a chunk in live streaming?

* Mesh architecture, you need up to 4 peers to support live streaming.
Assembling a stream from up to 4 peers, that are chunks. Latency up to
90 seconds.
* It is possible, that different layers of quality are provided from
different chunks.
* Wolfgang Beck: You can take advantage of structure of video stream,
e.g. I-Frame. I have missed this, or do you look at this. Would be
useful, it’s missing in multicast today.

Metadata Concept:

* Metadata concept is missing in the slides.
* Negotiations between peers about contents and algorithm to be
supported could provide more flexible solutions.

Media Transmission:

* Jörg Ott: Missing is the part for transmission of media across the network.

P2p technogoy for live streaming, multimedia traffic and file sharing:

* Henning Schulzrinne: Focusing just on the live streaming part is too
narrow, additional Pause and Rewind mode and real Video on Demand
should be included. Distinction seems artificial.
* Different opinions on technology synergies between live streaming,
multimedia and file sharing:
o Multimedia and Live streaming are different, similar or identical.
o Robert Bennett: What are the differentiator to file sharing and
multimedia transport
* James Seng: Architecture and protocols are different for live
streaming and VoD.
* Differences between Streaming and File Sharing:
o Knowledge of length
o How to get chunks in right order for live streaming? Typical
download has 10 to 30% redundancy.

Standardisation of a predefined solution:

* Henning Schulzrinne: Its obvious, that you have a special solution
in mind. We should first talk about problems and requirements.
Everybody can learn from implementation experience. We do not know,
how different this is from p2psip. We do not know, if we need a
separate solution in this case. We do not want to re-invent a new
version of TCP.
* James Seng: General impression, that PPLIVE want to have
standardized the own solution in IETF. That is wrong. We are here just
to help to find a reasonable solution. We have no consensus in the
company to do this. There is a big step to change a server/client
solution for streaming towards a p2p solution. China mobile trying to
solve a p2p streaming protocol. Most important part is combining
different streams to a single stream. We are trying to transport a
stream from n to n. Today different provider use different transport
protocol for this purpose. The working group needs to concentrate on
more narrow problem.

Focus Change:

* Henning Schulzrinne: I like modular design, to be able to reuse
components. Most protocol parts are available already. The motivation
for the WG is still confusing.
* Richard Bennett: Problem: You have bundled 3 problems and bind them together.
* James Seng: Signaling and transport problem have to be treated separated.
* Rony Even: We should describe the problem and the architecture, the
solution comes later. We should concentrate on slide with standardized
interactions. We should not decide on solutions today.
* Gonzalo Camarillo: Talking about signaling and transport is too
general. Graph, Flow, Media delivery should be describe too understand
the issue.
* There was consensus that the scope of the group should be narrowed down.
* We should first identify parts of the solution (functionality of the
components, architecture and protocol requirements, define challenges
for live streaming) and decide, which parts have to be solved and
where (in existing WGs or new WGs – This is work for more then one
WG). Correlation to other Wgs (e.g. AVT or WGs in application or
transport are) for the next event is too early, we need first more
information about the scope.

Additional Comments:

* Christer Homberg: How is this related to DNS?
* DNS is the archictural assumption for this problem.
* You are looking on a solution for streaming. Why is p2p a good
solution for? What is you objective?
* We have several motivations for using p2p for this purpose, e.g. scalability.

Summary:

* As in Minneapolis about 40 participants, including Gonzalo Camarillo
* Strong interest from the community in the topic as such
* Consensus, to narrow down the scope of the group
* Consensus, to work for a proper BOF at the next IETF in Stockholm.
* Slides of this meeting will be made available in the ppsp mailing list.

---
Notes taken by Vijay Gurbani

Agenda bashed - asked for more time to discuss problem statement.

Problem statement
Background presented.

Question: should privacy and content protection be part of work?

Benefits of standardizing: many for users, ISPs, network providers,
content providers, R&D, and market.

Problems to solve:
1) Interop of streaming services - many clients, many services, not
all services availaible on all clients. The NXN problem. Discussion
ensured on how interop will be fostered. Do we need a standard
to foster interop, or will interop will drive a standard?
2) Caching p2p stremaing data - How to cache when protocols differ?
3) Supporting mobile and low-bw peers - Mobile endpoints have a access
bottleneck; there is no p2p channel directly between the mobile
endpoints.

Discussion ensued on whether the content is live or is it static
content that is being distributed.

What will we standardize:
1) ???

2) Transporrt - payload between peers; no strawman proposal yet.
Will evaluate existing transport protocols and the specify or
develop a new protocol if needed.

Relationship to other WGs: p2psip, alto, and p2prg. Maybe need
to work with avt WG as well.

Why is IETF the right place? This is an Internet-wide protocol
and we have a group of interested people who are willing to work
on this problem.

Henning: Problem could be specified more clearly -- focusing just
on the live part is narrow. People will have Tivo-like functionality.
People will want to pause, rewind, etc. Then live streaming
looks like Video on demand. Protocol components need to be
identified more crisply. Need modular design rather than one big
protocol ball. Several sub-problems hidden here.

Conclusion: Goal is to form a WG to standardize an open p2p streaming
protocol. Deliv: ppsp arch, pspp signaling protocol and
ppsp transport protocol.

The chairs asked if people were still confused about the problem
statement. The consensus was yes. Re-iterated the three
problems to solve. Discussion ensued on what is a p2p streaming
protocol.

Richard Bennett: Break into component parts. Deal w/ p2p transport
problem (being dealt in ledbat WG.) Another problem is to deal
with bw constrained devices. Separate problem.

Henning: It is obvious you have a solution in mind; let's talk
about problem rather than a solution.

Chair: No solution in mind. We know the streaming protocols
being used on the Internet today. These use different protocols.
Do we need to standardized p2p streaming at all?

Henning: We do not know yet. We need to define who is talking
to who and what information they are conveying to each other.

Discussion ensued between RTSP and ppsp as signaling protocols.

Gonzalo: Divide things into smaller solutions and then compare them
with existing solutions first to see what we can reuse.

???: Diffrentiate yourself from how your solution is different
from standard multimedia file sharing.

Chair: We are not imposing or pushing a solution from PPLIVE.
PPLIVE has not decided to submit any of the work to the IETF.
Helping out the Yunfei. PPLIVE has no consensus to submit
any draft in IETF. ppsp may reuse some of the work like
rtsp, some from avt, etc. ppsp problem is that vide is not
on the wire as a single stream. Different streams are
assembled in a single stream.

Henning: Need to tease out the pieces carefully.

Christer: How is dsn draft related to t

Chair: It is the architectural assumption for this work.

Richard: Would you be here if your network was not being hammered
for upload?

Yunfei: This is a problem that many mobile operators are having.

Richard: Take this problem and break it down into 6-7 parts.
Of those parts, which one is most urgent and important to you.

Consensus from this discussion: narrow down the problem statement
and focus.

Talk: PPSP Requirements

Discussion ensued on whether multicast can be used.

Haiyong Xie: Still do not see the major difference between ppsp and
file sharing. No info exchanged for specific streams regarding
video signals. It looks like a file sharing protocol.

Second comment: why are you talking about ppsp? Key problem is
to stream vide to N users. Why p2p is a good solution here?
China Mobile wants to solve the problem of controlling p2p traffic.
10% of traffic comes from pplive. So, what's the motivation of
having p2p in "ppsp?" What is your objectvice.

Yunfei: We have launched mobile TV, which may have scalability
problems. Therefore we look to p2p technolgies to attack this.

Chair asked if the room wanted discussion or move on to other
presentations in the last 25 minutes. Room decided to move on.

Yunfei, Compare PPLIVE and PPSTREAM

Measurements on how to evaluate system performance. Went over
the methodology to collect measurement data. Went through
the slides that compare and contrast these two architectures
(see slides.)

The chairs decided to devote the last 15 minutes to driving
a sense of what the BoF attendeed want to do. Consensus
calls by chair:

There was a show of hands on the scope of ppsp being narrow.

Discussion ensued on how to help narrow down the scope. Do an
architectural diagram to see who is making the request of whom,
what is the result of that request, etc.

What is the biggest challenge in live streaming? Compare this
to file streaming.

Consensus to clarify the architecture a bit more, break it down
into different components. See which component is being worked
in which group.

No consensus to charter this as a WG.

But there is consensus to create a real BoF in the next IETF to
present the problem statement, system architecture for the next
IETF.