[Docs] [txt|pdf] [Tracker] [Email] [Nits]

Versions: 00 01 02

PPSP                                                      Yunfei.Zhang
Internet Draft
Intended status: Informational                            China Mobile
Expires: September 2009                                    March 3, 2009



    Protocol Analysis and Comparison of PPlive and PPstream by Internet
                                Measurement
          draft-zhang-ppsp-protocol-comparison-measurement-00.txt


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on August 3, 2009.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the document
   authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.






Zhang                 Expires September 3, 2009               [Page 1]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


Abstract

   In this draft we introduce an Internet measurement work for both
   pplive and ppstream. First, we give a brief introduction about our
   motivation and target of this measurement. We then introduce the
   methodology, platform, data and modeling of our measurement. Finally
   we outline the p2p media streaming protocols by the measurement.








































Zhang                 Expires September 3,2009                [Page 2]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


Table of Contents


   1. Introduction................................................4
   2. Motivation and Target of the Measurement.....................5
   3. Methodology of Our Measurement...............................6
   4. Measurement Platforms........................................8
   5. Data Analysis and Modeling..................................10
   6. Study of P2P Media Streaming Protocols by the Measurement....10
      6.1. PPLive Live Streaming:.................................10
      6.2. PPLive VoD............................................11
      6.3. PPStream Live (early version, TCP).....................12
      6.4. Conclusion............................................12
   7. Security Considerations.....................................14
   8. References.................................................15
      8.1. Normative References...................................15
      8.2. Informative References.................................15
   Intellectual Property Statement....................
   Disclaimer of Validity............................




























Zhang                 Expires September 3,2009                [Page 3]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


1. Introduction

   P2p media streaming is one of the most popular p2p system and is a
   new developing trend for modern video system. More and more users,
   vendors as well as researchers have been attracted to it. Currently,
   there are many such systems on Internet, such as PPLive, PPStream,
   UUSee, etc. Usually all of them can provide Live and VoD programs to
   users. They have a similar system structures according to our
   measurement. In good network conditions, all of them can bring good
   experiences to users; once the stable condition is broken, the p2p
   applications will present different performance.




































Zhang                 Expires September 3,2009                [Page 4]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


2. Motivation and Target of the Measurement

   Naturally, we care about how to evaluate system performance, what the
   performance limitations are under current system models, how to
   decrease the pressure on the network. In order to answer these
   questions, we study the following aspects of p2p streaming systems:

   1.To extract the general p2p media streaming system structure;

   2.To analyze and evaluate the signaling (protocol) messages ( types,
   format, function, exchange sequence)

   3. To study and model the core mechanism such as initial buffer lag
   policy, buffer cache schedule policy, data fetching policy, etc;

   4.To optimize the system performance and improve network robustness;

   5.To study its effect on physical layer network, transport lay
   protocol ( TCP and UDP );

   6.To study new p2p suitable transport protocol instead of application
   lay p2p transportation;

   7.To study the availability of current p2p streaming systems on
   mobile ip;

   8.To present related standard suggests.




















Zhang                 Expires September 3,2009                [Page 5]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


3. Methodology of Our Measurement

   Real network based measurement is important in studying p2p media
   streaming systems. However all current commercial p2p media streaming
   systems are propriety protocol systems without any public document
   about system' working mechanism available. Although some researchers
   report some useful finds, most of our concerns are not resolved yet.
   We have to firstly deeply understand how the system works. Usually we
   use certain reverse-engineering method to analyze its working
   principle. In the protocol cracking, we mainly focus on the top 2 of
   very popular p2p streaming systems - PPLive and PPStream. Beside
   their popular degree, several other reasons make them as the starting:
   Both of them use plain text in their protocol exchanging; both udp
   and tcp are adopted; both of them are the new generation data driven
   p2p streaming systems.

   Our reverse engineering are conducted in following 3 stages:

   Firstly, by tracing a standard client, we capture interactive packets
   between the local peer and others with ethereal/windump tool. Based
   on our experience on the p2p streaming system, some basic protocol
   types must be included such as buffer map, chunk request/response,
   shake hand packet, etc. For each udp packet, it is reasonable to
   assume that each packet is a completed protocol message, while for
   tcp packets we must extract messages from all application data stream.
   Usually we can get the rough protocol format by matching traced
   packets to the known basic protocol types. But there are still many
   unknown details left.

   Secondly, the traced data is fed into our dumping tool, which can
   filter data into a text file with composed conditions, such as source
   ip/port, destination ip/port, VoD/Live protocol type. Through
   inspecting the text file of different channels, we find many regular
   changes that help us in parsing the protocol format in details. Of
   course, there is still one-third irregular data. In this case, we
   guess and try it based on our experiences in next step. At last, we
   parse about nearly 90% of PPLive and PPStream protocols. In PPLive
   system, there are about 15 message types, all of that haven't any
   clearly protocol marks in order to escape from restrictions ISPs may
   imposed on (we think). Among these types, buffermap and peerlist
   messages are the most useful messages for us to measure and analyze
   the system.

   At the third stage, we analyze the time sequences of the protocol
   messages. Some communication time sequence is obvious, such as chunk
   request/response, while others are not. In later case, we guess and


Zhang                 Expires September 3,2009                [Page 6]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


   try differently composed events until a sequence makes right sound.
   Ultimately, all time sequences in communications are resulted
   successfully.












































Zhang                 Expires September 3,2009                [Page 7]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


4. Measurement Platforms

   For different analysis, we take different measurement methods. In
   general, our environment consists of 4 dell pc servers in a private
   ip space (LAN) behind a 6mbps ADSL NAT router. each of which has
   2.8Hz Pentium CPU, 1MB memory, 80GB hard disk, 10/100Mbps Ethernet,
   windows OS, mysql database.



   +------------------------------------------------+
   |  crawler         tracker server         peer   |
   |     |                   |                 |    |
   |     |    Shake hand     |                 |    |
   |     |------------------>|                 |    |
   |     |  Peerlist request |                 |    |
   |     |------------------>|                 |    |
   |     |  Peerlist response|                 |    |
   |     |<------------------|                 |    |
   |     |                   |                 |    |
   |     |Notification for connecting a peer X |    |
   |     |------------------>|                 |    |
   |     |         Shake hand to peer x        |    |
   |     |-------------------|---------------->|    |
   |     |         Buffermap of peer x         |    |
   |     |<------------------|-----------------|    |
   |     |                   |                 |    |
   |     |Notification for connecting a peer y |    |
   |     |------------------>|                 |    |
   |     |         Shake hand to peer y        |    |
   |     |-------------------|---------------->|    |
   |     |         Buffermap of peer x         |    |
   |     |<------------------|-----------------|    |
   |     |                   |                 |    |
   +------------------------------------------------+

                Figure 1   Protocol sequence for crawling

   1. Official client trace: use tcpdump/windump/wireshark to capture
   exchanging packets between local peer and other peers.

   2. System topology crawler: based on p2p streaming protocol, design
   legal measurement tool to detect the whole network in short time. We
   usually take some measures improve the probing efficiency such as
   multi threads, fast data searching in memory, multi-tables in



Zhang                 Expires September 3,2009                [Page 8]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


   databases, master-slave distribution deployment, concurrent tcp
   session limitation enlargement.

   3. Long term multi online peers probe: different from topology
   crawler, it will probe a certain online peers in a long term in order
   to collect the detail information of these peers. Usually more
   complete protocol set should be realized in it.

   4. P2p streaming client measurement in mobile ip: A fix position PC
   is used as the mobile device, where three types of software have been
   installed: p2p streaming client software; packet capture software;
   our mobile ip simulation software.

   5. Special client accessing to official network in order to evaluate
   the system robusticity and optimize the protocol: based on
   protocols,we build the legal p2p client to join in the official p2p
   network. By this client, we can test and evaluate new protocol design
   and new core system models.






























Zhang                 Expires September 3,2009                [Page 9]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


5. Data Analysis and Modeling

   As for data analysis and modeling, we have made some progress and
   published some papers [1]~[6]. Interested readers can refer to them
   for more details.



6. Study of P2P Media Streaming Protocols by the Measurement

   We have measurement PPLive and PPstream and guessed the protocols
   both for live streaming and VoD streaming respectively. However due
   to some encryption(It's said to be Scrambling), VoD streaming data
   from PPStream hasn't been analyzed yet. We list the signaling
   transaction of pplive live streaming and VoD and ppstream live
   streaming as follows:

6.1. PPLive Live Streaming:

   Messages with Tracker

   0101 (peer registration)

   0100 (tracker response)

   0201 (peerlist request)

   0200 (peerlist response)

   0301 (tracker offset request)

   0300 (tracker offset response)

   Messages with Peer

   0x4101 (peerlist request)

   0x 4201 (peerlist response)

   0x 5400 (peerlist response)

   0x 4400 (Buffermap response)

   0x 5200 (chunk request)

   0x 5300 (chunk response)


Zhang                 Expires September 3,2009               [Page 10]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


   0x 4601 (chunk response)

   0x 6101 (chunk request)

   0x6201 (chunk response)

   0x 4000 (disconnect)

   0x4500 (chunk request)

   0x4901 (udp handshake)

   0x4400: update/5s

6.2. PPLive VoD

   0x04 (peers_data_request)

   0x05 (peers_data_response_1)

   0x06 (peers_data_response_2)

   0x11 (peers_peerlist_request)

   0x12 (peers_peerlist_response)

   0x13 (peers_shakehand)

   0x14 (peers_bitfield)

   0x16 (trk shakehand)

   0x17 (trk notification of a peer)

   0x18 (peers_keepalive)

   0x43 (host_ip)

   0x44 (public_ip)

   0x51 (host_ip_format2)

   0x52 (public_ip_format2)





Zhang                 Expires September 3,2009               [Page 11]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


6.3. PPStream Live (early version, TCP)

   0x02 (buffermap)

   0x22 (buffermap)

   0x03 (chunk request)

   0x04 (chunk response)

   0x05 (nochunk response)

   0x08 (peerlist request)

   0x09 (peerlist response)

   0x40 (media information)

   0x1d (client version)

   0x10 (protocol error information)

   0x1b (remote live time)

   0x1  (peer id)

   0x19 (remote refuse)

   0xA0 (vod bitmap)

6.4. Conclusion

   Both PPLive and PPStream support Live and VoD programs, and have
   similar system structures. As for the signaling protocol, both
   systems have similar process. We have depicted the interactions
   between peers and peers as well as trackers in the problem statement
   draft. Interested readers can refer to draft-zhang-ppsp-problem-
   statement for details.

   However, there are still some difference between pplive and ppstream
   which belongs to their high secrets. For example, in the buffer
   aspect, pplive is a large buffer system, which can smooth time delay
   jitters but contributes to relative large startup delay. The chunk
   fetch policy is seqential fetcing and rarest first at same time. The
   schema of the buffer is a variable length in chunks but fixed length
   in playback time. The buffer map schedule is simple based on chunks


Zhang                 Expires September 3,2009               [Page 12]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


   id. On the other hand, PPStream is a small buffer system (early
   version), which has small startup delay but leads to video freeze
   with large jitters. The chunk fetch is randomly in each buffer window.
   The schema of the buffer is of multi playable media blocks with fixed
   playback time (mulit buffers) for each of them. Hence its buffer
   schedule is based on multi buffer windows, where each chunk is
   uniquely marks indicated by the buffer window offset and the internal
   chunk id. According to our understanding, the mechanism of PPStream
   is a litter complex.






































Zhang                 Expires September 3,2009               [Page 13]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


7. Security Considerations

   We don't involve security measurement till now.












































Zhang                 Expires September 3,2009               [Page 14]


Internet-Draft          Protocol Analysis and Comparison of PPlive and
PPstream by Internet Measurement                            March 2009


8. References

8.1. Normative References

   [1]  Y. Chen, C. Chen and C. Li, "A Measurement Study of Cache
         Rejection in P2P Live Streaming System", Workshop on Multimedia
         Network Systems and Applications in conjunction with ICDCS-2008,
         June, 2008, Beijing, China

   [2]  Y. Chen, C. Chen and C. Li, "Measure and Model P2P Streaming
         System by Buffer Bitmap", HPCC '08, Sept. 2008, Dalian, China

   [3]  Cx.Li,Cj.Chen ''Fetching Strategy in the Startup Stage of p2p
         Live Streaming'', http://arxiv.org/abs/0810.2134

   [4]  Cx.Li,Cj.Chen ''Initial Offset Placement in p2p Live Streaming
         Systems'' http://arxiv.org/abs/0810.2063

   [5]  Cx.Li,Cj.Chen ''Inferring Playback Rate and Rate Resets of p2p
         Video Streaming Transmissions by Piecewise Line Envelope
         Approximation'' The Journal of China Universities of Posts and
         Telecommunications March.2009

   [6]  Cx.Li,Cj.Chen ''Real P2P System Measurement under Mobile IP
         Environment'' accepted by icnds2009

8.2. Informative References

Author's Addresses

   Yunfei Zhang
   China Mobile

   Phone: 86 13601032119
   Email: zhangyunfei@chinamobile.com












Zhang                 Expires September 3,2009               [Page 15]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/