PPSP Y. Zhang Internet-Draft China Mobile Intended status: Standards Track N. Zong Expires: April 23, 2010 Huawei Technologies G. Camarillo Ericsson J. Seng PPLive R. Yang Yale University October 20, 2009 Problem Statement of P2P Streaming Protocol (PPSP) draft-zhang-ppsp-problem-statement-05 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. 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 April 23, 2010. Zhang, et al. Expires April 23, 2010 [Page 1] Internet-Draft PPSP PS October 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract We propose to standardize the key signaling protocols among various P2P streaming system components including the tracker and the peers. These protocols, called PPSP, are a part of P2P streaming protocols. This document describes the terminologies, concepts, incentives, and scope of developing PPSP, as well as the use cases of PPSP. Zhang, et al. Expires April 23, 2010 [Page 2] Internet-Draft PPSP PS October 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Research or engineering . . . . . . . . . . . . . . . . . 5 1.3. Objective of the PPSP work . . . . . . . . . . . . . . . . 5 2. Terminology and concepts . . . . . . . . . . . . . . . . . . . 5 3. Introduction of P2P streaming system . . . . . . . . . . . . . 6 4. Incentives for developing standard PPSP . . . . . . . . . . . 8 4.1. P2P streaming and edge cache/CDN support . . . . . . . . . 9 4.2. Incentive for ISPs . . . . . . . . . . . . . . . . . . . . 9 5. Components of P2P streaming system . . . . . . . . . . . . . . 10 6. Scope of PPSP . . . . . . . . . . . . . . . . . . . . . . . . 11 6.1. Protocols to be standardized . . . . . . . . . . . . . . . 11 6.2. Service types to be considered . . . . . . . . . . . . . . 13 7. Use cases of PPSP . . . . . . . . . . . . . . . . . . . . . . 13 7.1. Worldwide Provision of P2P Streaming Service with PPSP . . 13 7.2. Hierarchical P2P Streaming Distribution with PPSP . . . . 15 7.3. Unified client software to watch P2P Streaming Programs . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 10.1. Normative References . . . . . . . . . . . . . . . . . . . 17 10.2. Informative References . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Zhang, et al. Expires April 23, 2010 [Page 3] Internet-Draft PPSP PS October 2009 1. Introduction 1.1. Background Streaming traffic is among the fastest growing traffic on the Internet. In a recent white paper, Cisco predicts that by 2012, 90% of all Internet traffic will be video [Cisco]. There are two basic paradigms for delivering streaming traffic on the global Internet: the client-server paradigm and the peer-to-peer (P2P) paradigm [P2PStreamingSurvey]. A particular advantage of the P2P paradigm over the client-server paradigm is its scalability. As an example, PPLive [PPLive], one of the largest P2P streaming vendors, is able to distribute large-scale, live streaming programs such as the CCTV Spring Festival Gala to more than 2 million users with only a handful of servers. CNN [CNN] reported that P2P streaming by Octoshape played a major role in its distribution of the historic inauguration address of President Obama. It is well demonstrated in practice that P2P streaming can deliver videos encoded at a rate of about 400 Kbps, in the presence of churn, with positive user experiences. In light of these technical advantages, P2P streaming is seeing rapid deployment. Large P2P streaming applications such as PPLive [PPLive], PPstream [PPstream] and UUSee [UUSee] have each reached a number of installations exceeding 100 millions. P2P streaming traffic is becoming a major type of Internet traffic in some Internet networks. For example, according to the statistics of a major Chinese ISP, the traffic generated by P2P streaming applications exceeded 50% of the total backbone traffic during peak time in 2008. There are reports that major video distributors such as Youtube [youtube] and tudou [tudou] are conducting trials of using P2P streaming as a component of their delivery infrastructures. Given the increasing integration of P2P streaming into the global content delivery infrastructure, the lack of open standard P2P streaming protocol has become a major missing component in the Internet protocol stack. Multiple similar but proprietary P2P streaming protocols result in repetitious development efforts and lock-in effects. More importantly, it leads to substantial difficulties when integrating P2P streaming as a component of a global content delivery infrastructure. For example, proprietary P2P streaming protocols do not integrate well with infrastructure devices such as caches and other edge devices. Zhang, et al. Expires April 23, 2010 [Page 4] Internet-Draft PPSP PS October 2009 1.2. Research or engineering As [P2PStreamingSurvey] identifies, there exist multiple proprietary P2P streaming systems including PPLive, PPstream, UUsee, abacast, and Coolstreaming. A natural question to ask is whether the development of P2P streaming is mature and ready for standardization. We admit that P2P streaming will continue to improve and evolve. However, our investigation shows that existing P2P streaming systems are largely converging, sharing similar architecture and signaling protocols [draft-zhang-ppsp-protocol-comparison-measurement-00]. The competition of P2P streaming vendors is focusing increasingly on content. 1.3. Objective of the PPSP work Multiple protocols such as streaming control, resource discovery, streaming data transport, etc. are needed to build a P2P streaming system [P2PStreamingSurvey]. We call those protocols P2P streaming protocols. The objective of the PPSP work is to standardize the key signaling protocols among various P2P streaming system components including the tracker and the peers. These protocols, called PPSP, are a part of P2P streaming protocols. Note that the complete set of standard P2P streaming protocols for a whole P2P streaming system could be developed following or parallel to the PPSP work. PPSP will serve as an enabling technology, building on the development experiences of existing P2P streaming systems. Its design will allow it to integrate with IETF efforts on distributed resource location, traffic localization, and streaming control mechanisms. It allows effective integration with edge infrastructures such as cache and mobile edge equipment. This document describes the terminologies, concepts, incentives, and scope of developing PPSP, as well as the use cases of PPSP. The rest of this document is organized as follows. In Section 2, we introduce some common terminologies and concepts. In Section 3, we introduce P2P streaming system. In Section 4, we identify the incentives for developing standard P2P streaming protocols. In Section 5, we describe the components of P2P streaming system. In Section 6, we outline the main scope of PPSP. In Section 7, we list some use cases of PPSP. 2. Terminology and concepts Chunk: A chunk is a basic unit of partitioned streaming, which is used by a peer for the purpose of storage, advertisement and exchange Zhang, et al. Expires April 23, 2010 [Page 5] Internet-Draft PPSP PS October 2009 among peers [Sigcomm:P2P streaming]. Content Distribution Network (CDN) node: A CDN node refers to a network entity that usually is deployed at the network edge to store content provided by the original servers, and serves content to the clients located nearby topologically. Live streaming: The scenario where all clients receive streaming content for the same ongoing event. The lags between the play points of the clients and that of the streaming source are small. P2P cache: A P2P cache refers to a network entity that caches P2P traffic in the network, and either transparently or explicitly as a peer distributes content to other peers. P2P streaming protocols: P2P streaming protocols refer to multiple protocols such as streaming control, resource discovery, streaming data transport, etc. which are needed to build a P2P streaming system. Peer/PPSP peer: A peer/PPSP peer refers to a participant in a P2P streaming system. The participant not only receives streaming content, but also stores and uploads streaming content to other participants. PPSP: PPSP refer to the key signaling protocols among various P2P streaming system components including the tracker and peer. PPSP are a part of P2P streaming protocols. Swarm: A swarm refers to a group of clients (i.e. peers) sharing the same content (e.g. video/audio program, digital file, etc) at a given time. Tracker/PPSP tracker: A tracker/PPSP tracker refers to a directory service which maintains lists of peers/PPSP peers storing chunks for a specific channel or streaming file and answers queries from peers/ PPSP peers for peer lists. Video-on-demand (VoD): The scenario where different clients watch different parts of the media recorded and stored during past events. 3. Introduction of P2P streaming system There are multiple available P2P streaming solutions. Some are deployed solutions, while others are still under active study. A survey of existing solutions can be found in [Survey]. Zhang, et al. Expires April 23, 2010 [Page 6] Internet-Draft PPSP PS October 2009 In P2P streaming system, there are various swarms with each swarm containing a group of clients sharing same streaming content (e.g. channel, streaming file, etc) at a given time. These clients are called peers, as each client not only receives streaming content, but also stores and uploads streaming content to other clients. In a broad sense of global content delivery infrastructure, peers can include multiple types of entities such as end user applications, caches, CDN nodes, and/or other edge devices. Therefore, the basic functions of a P2P streaming system involve: 1) Maintaining information about which peers in which swarm in some directory service, a.k.a. tracker. 2) In each swarm, exchange information about content availability (e.g. which chunks stored by a peer) among peers, or between tracker and peer. 3) In each swarm, exchange the actual content among peers. As shown in Figure 1, common information flows in a P2P streaming system include: 1) When a peer wants to receive streaming content: 1.1) Peer acquires a list of peers in the swarm from the tracker. A swarm can be indexed by a channel ID, streaming file ID, etc. 1.2) Peer exchanges its content availability with the peers on the obtained peer list. 1.3) Peer identifies the peers with desired content and requests for the content from the identified peers. 2) When a peer wants to share streaming content with others: 2.1) Peer sends information to the tracker about the swarms it belongs to, plus streaming status and/or content availability. Zhang, et al. Expires April 23, 2010 [Page 7] Internet-Draft PPSP PS October 2009 +----------------------------------------------------+ | +-------------------+ | | | Tracker | | | +-------------------+ | | ^ | ^ | | | | |swarms, | | query | | peer list |streaming status| | | | |and/or content | | | | |availability | | | V | | | +-------------+ +------------+ | | | Peer1 |<------->| Peer 2 | | | +-------------+ content +------------+ | | ^ ^ availability | | * | content | | content * |availability | | * V | | +------------+ | | | Peer 3 | | | +------------+ | +----------------------------------------------------+ Figure 1, Common information flows in P2P streaming system 4. Incentives for developing standard PPSP We start by considering the success of the Web. It is the standard HTTP protocol that makes it possible to deploy the global content distribution eco-system that consists of not only end devices such as Web servers and Web clients, but also infrastructure devices such as Web caches and CDN nodes. All of these devices communicate through standard protocols and provide substantial benefits to the consumers, the content publishers, and the network infrastructure. As we discussed in Section 1, given the increasing integration of P2P streaming into the global content delivery infrastructure, proprietary P2P streaming protocols not only result in repetitious development efforts and lock-in effect, but also leads to substantial difficulties when integrating P2P streaming as an integral component of a global content delivery infrastructure. For example, interactions between proprietary P2P streaming protocols and infrastructure devices pose substantial problems. Standard PPSP address these problems and thus provide strong incentives. Zhang, et al. Expires April 23, 2010 [Page 8] Internet-Draft PPSP PS October 2009 4.1. P2P streaming and edge cache/CDN support In the context of P2P streaming, infrastructure devices such as edge caches and CDN nodes are also shown as promising means to both improve the performance of P2P streaming (e.g., lower latency) by providing more stable "super peers" and reduce traffic in ISP network [draft-marocco-alto-problem-statement-03][CDN+P2P]. However, there can be substantial obstacles in deploying infrastructure edge devices supporting proprietary P2P streaming protocols [HTPT]. Unlike the Web with the standard HTTP protocol, the current P2P streaming landscape consists of multiple, proprietary P2P streaming protocols mostly differing in signaling transactions. Consequently, in order to support P2P streaming, the infrastructure devices need to understand and keep updated with various proprietary P2P streaming protocols. This introduces complexity and deployment cost of infrastructure devices. With standard PPSP, edge caches and CDN nodes can be designed to inter-operate with only the standard protocols, reducing the complexity and cost to support streaming involving P2P. 4.2. Incentive for ISPs Mobility and wireless are becoming increasingly important features to support in future Internet deployments [GENI], [FIND]. For example, China Mobile is developing the Distributed Services Network (DSN) strategy to build its mobile Internet [draft-zhang-ppsp-dsn-introduction-00]. Along with the introduction of mobile and wireless capabilities into the Internet, mobile streaming is becoming a key offered service [MobileTV]. In Korea the number of mobile TV subscriber has reached seventeen millions, accounting for one third of the mobile subscribers. In Italy, there are one million mobile TV users. During the 2008 Beijing Olympic Games, more than one million users utilize China mobile's mobileTV service. Although most current mobile TV deployments are developed in the traditional client/server model, there are clear interests in integrating streaming systems involving P2P into mobile streaming, due to content availability, scalability, and robustness of P2P systems. However, mobile Internet may face more severe bandwidth limitations for supporting P2P streaming. There can be multiple bottlenecks where bandwidth can be limited and the transmission cost can be quite high: a) between mobile terminals and mobile access nodes; b) between mobile access nodes; c) between the mobile network and the fixed network. Zhang, et al. Expires April 23, 2010 [Page 9] Internet-Draft PPSP PS October 2009 Standard PPSP can help to address the above challenges. With PPSP, infrastructure devices like mobile gateways and access points can be acted as "Super Peers" and deployed to interact with mobile streaming applications to substantial reduce bandwidth usage on key bottlenecks. It is worth mentioning at this point that the development of PPSP should consider the requirements of mobile Internet. For example, the overhead of PPSP be small in low bandwidth mobile Internet. Also, information exchange in PPSP should support mobility, low battery and heterogeneous capabilities of mobile terminals. Systematic requirements on the development of PPSP will be addressed in the requirements documents. 5. Components of P2P streaming system +--------------------------------------------------+ | Application Layer | |--------------------------------------------------| | Play-out Layer | | +----------+ +------------+ +-----------+ | | |start/stop| |pause/resume| | FF/rewind | | | +----------+ +------------+ +-----------+ | |--------------------------------------------------| | Information Layer | | +------------+ +------+ +-----------+ | | |registration| |report| | statistics| | | +------------+ +------+ +-----------+ | |--------------------------------------------------| | Communication Layer | | +---------------------+ +------------------+ | | |tracker communication| |peer communication| | | +---------------------+ +------------------+ | | +-------------+ | | | bootstrap | | | +-------------+ | |--------------------------------------------------| | Transport Layer | +--------------------------------------------------+ Figure 2, Components of P2P streaming system To organize our efforts, we show the components of a complete P2P streaming system in Figure 2. Note that the components in this figure are considered as functional blocks of P2P streaming system. The inter-communication between different layers is for further study. Zhang, et al. Expires April 23, 2010 [Page 10] Internet-Draft PPSP PS October 2009 1) Transport Layer is responsible for data transmission between peers. UDP, TCP or other protocols can be used. 2) Communication layer includes three components: 2.1) Tracker communication is a component that enables each peer to get peer list from the tracker and/or provide content availability to the tracker. 2.2) Peer communication is a component that enables each peer to exchange content availability and request other peers for content. 2.3) Bootstrap is a component that enables newly joined nodes to obtain tracker information. 3) Information layer is responsible for peer and content information collection and management. 3.1) Registration is a component that enables nodes to register to the system, and publish the content information. The information may include but is not limited to: content description, content type, creation time, node information such as physical location, IP address. 3.2) Report is a component that enables peers to report streaming status to the tracker. The information may include peer inbound/ outbound traffic, amount of neighbor peers, peer health degree and other streaming parameters. 3.3) Statistics is a component that enables trackers to manage the aggregated system information for global control in upload bandwidth consumption, overhead consumption and other regards. 4) Play-out layer is responsible for controlling the action of media play (e.g. start, pause, resume, stop, fast-forward, and rewind). 5) Application layer is the top layer for streaming applications. 6. Scope of PPSP 6.1. Protocols to be standardized We propose to standardize protocols in PPSP which enable the tracker communication and the peer communication components in the communication layer, as well as the report component in the information layer. These protocols, called PPSP, are key mechanisms involving two important roles - tracker and peer in P2P streaming Zhang, et al. Expires April 23, 2010 [Page 11] Internet-Draft PPSP PS October 2009 processes, as addressed in Section 3. These signaling protocols,in essence, aim at standardizing the content information exchange mechanisms among different devices in P2P streaming systems. Note that PPSP are only a part of P2P streaming protocols. The complete set of standard P2P streaming protocols for a whole P2P streaming system could be developed following or parallel to the PPSP work. Because bootstrap, registration and statistics components are out-of- band mechanisms for streaming processes, they are not in current scope of PPSP. Both transport, play-out and application layers in P2P streaming system are also beyond the current scope of PPSP. Therefore, PPSP include the PPSP tracker protocol - a signaling protocol between PPSP trackers and PPSP peers, and the PPSP peer protocol - a signaling protocol among PPSP peers. 1) PPSP tracker protocol This protocol will define: 1.1) Standard format/encoding of information between PPSP peers and PPSP trackers, such as peer list, content availability, streaming status including online time, link status, node capability and other streaming parameters. 1.2) Standard messages between PPSP peers and PPSP trackers defining how PPSP peers report streaming status and request to PPSP trackers, as well as how PPSP trackers reply to the requests. Note that existing protocols should be investigated and evaluated for being reused or extended as the messages between tracker and peer. Possible candidates include the use of the HTTP, where the GET method could be used to obtain peer lists, the POST method used for streaming status reports, etc. 2) PPSP peer protocol This protocol will define: 2.1) Standard format/encoding of information among PPSP peers, such as chunk description. 2.2) Standard messages among PPSP peers defining how PPSP peers advertise chunk availability to each other, as well as the signaling for requesting the chunks among PPSP peers. Again, existing protocols should be investigated and evaluated for being reused or extended as the messages among peers. Possible Zhang, et al. Expires April 23, 2010 [Page 12] Internet-Draft PPSP PS October 2009 candidates include the use of the HTTP, where the GET method could be used to obtain chunk availability, etc. Considering the potential large number of peers, some lightweight (possibly binary) protocols could also be good candidates. 6.2. Service types to be considered As stated in Section 1, PPSP will serve as enabling technology and tools for building various P2P streaming systems. We are not standardizing certain streaming services. The reason why we list service types here is to show we would consider the properties of these services as the requirements for PPSP design. Common service types supported by current P2P streaming systems include live streaming and video-on-demand (VoD). Note the services listed in this draft are not exhaustive, and more service types are to be involved during the PPSP work. In live streaming, all PPSP peers are interested in the media coming from an ongoing event, which means that all PPSP peers share nearly the same streaming content at a given point of time. In live streaming, some PPSP peers may store the live media for further distribution, which is known as TSTV (time-shift TV) where the stored media are separated into chunks and distributed in a VoD-like manner. In VoD, different PPSP peers watch different parts of the media recorded and stored during a past event. In this case, each PPSP peer keeps asking other PPSP peers which media chunks are stored in which PPSP peers, and then pulls the required media from some selected PPSP peers. 7. Use cases of PPSP 7.1. Worldwide Provision of P2P Streaming Service with PPSP Consider a popular program, for example the Chinese Spring Festival, where a P2P streaming provider is providing a live media broadcast from China. With existing deployments today, there is very little difficulty in watching the broadcast on the Internet from within China - this is already widespread practice. However if a viewer outside of China wants to watch the gala from outside China, they may have difficulties with smooth playback because of 1) Insufficient number of peers outside of China. 2) Instability of dynamic peers, which makes meeting condition 1 more difficult. Zhang, et al. Expires April 23, 2010 [Page 13] Internet-Draft PPSP PS October 2009 3) No stable end-to-end bandwidth assurance from the source to peers outside China. As stated in section 4, the hybrid CDN and P2P architectures can ease the above difficulties. With the help of PPSP, the P2P streaming provider can quickly leverage other CDN providers' coverage outside its deployment scope. For instance, it may partner with a US CDN provider to provide live streaming to the audience in the USA and may partner with yet another provider to provide services outside of that service provider's scope [Peering CDN] as shown in Fig3. PPSP helps by ensuring the providers have a common protocol to communicate. This reduces the case by case negotiation between the original provider and multiple CDN providers if otherwise proprietary protocols are used makes it easier for both sides to interoperate. The interactions between the P2P streaming provider's tracker server and CDN surrogates as well as interactions between CDN surrogates are the same as a normal peer as shown in Figure 3. This is very useful for a small streaming provider who has no its own CDN surrogates and much money to distribute its stream worldwide. Note that some ISPs have been/are deploying CDN nodes in private networks to improve the user experience. In this sense it's same as a CDN vendor. Zhang, et al. Expires April 23, 2010 [Page 14] Internet-Draft PPSP PS October 2009 +-------------------------------------------------------------------+ | | | +------------------------+ | | +------------->| Original Tracker |<--------+ | | | +------------------------+ | | | | ^ ^ | | | Tracker| Tracker | | Tracker |Tracker | |Protocol| Protocol| | Protocol |Protocol| | V V V V | | +---------+ Peer +---------+ +----------+ +---------+ | | | CDN1 |<-------->| CDN2 | | CDN2 | | CDN2 | | | | PoP2 | Protocol | PoP1 | | PoP1 | | PoP2 | | | +---------+ +---------+ +----------+ +---------+ | | ^^ ^ ^ | | Peer || Peer Protocol Peer Protocol | |Peer | |Protocol|+--------------+ +-----+ |Protocol | | V V V V | | +-------+ Peer +------+ +---------+ Peer +---------+| | | USA |<------->| USA | |Caribbean|<------>|Caribbean|| | | User1 |Protocol | User2| | User1 |Protocol| User2 || | +-------+ +------+ +---------+ +---------+| | | | | +-------------------------------------------------------------------+ Figure 3, Worldwide Provision of P2P Streaming Service with PPSP 7.2. Hierarchical P2P Streaming Distribution with PPSP The hierarchical P2P streaming distribution have many advantages over non-hierarchical conterparters such as better QoS(start-up latency and service interruption reduction[P2broadcast], higher throughput and lower packets drop ratio[Hybrid], topology-mismatch reduction and better management[AHLSS]. PPSP is useful for clustering the peers with abundant node information and content information exchange to be designed. The simplest hierarchical P2P streaming deployment is just similar to case 7.1 where CDN nodes are in the higher level. Note that PPSP can be applied both in flat and hierarchical P2P streaming distribution. 7.3. Unified client software to watch P2P Streaming Programs Currently the users have to install different client software in order to watch different P2P streaming programs since different vendors have generally different programs focus. For example, when a user watches CCTV5 on the Internet, a sports channel with high Zhang, et al. Expires April 23, 2010 [Page 15] Internet-Draft PPSP PS October 2009 popularity in Chinese, he may choose PPLive for watching. And when he turns to watch TV series, he tends to use PPStream software.This leads to a lot of P2P streaming software installed in the client. Things become worse in storage and memory constrained devices like mobile handset or TV setbox to install a lot of software. With the help of PPSP, a unified client software can understand different vendors supporting PPSP. Note that this won't affect each vendor's audience group since a user with a unified client watching different vendor's programs is viewed as different users from the vendors' point of view. 8. Security Considerations PPSP has a similar assumption in peer privacy as P2PSIP[ID.ietf- p2psip-base], i.e., all participants in the system are issued unique identities and credentials through some mechanism not in the scope of PPSP, such as a centralized server. Hence PPSP will not attempt a solution to these issues for P2P streaming networks in general. However PPSP have some unique security issues: 1) The content published by peers may not be checked by centralized certificating server. Therefore P2P streaming network may have the danger of malicious content distribution. 2) Content pollution is another common problem faced by P2P streaming. 3) Because there is a tracker who is critical to the P2P streaming systems. There is an increased probability that threats may involve launching attacks against the tracker. PPSP may include some mechanisms to prevent malicious nodes from polluting the streaming content or launch attacks to the tracker. The protocol documents will contain a complete description of the security/privacy concerns of PPSP. 9. Acknowledgements We would like to acknowledge the following who provided feedback or suggestions for this document: D. Bryan from Cogent Force; E. Marocco from Telecom Italia; V. Gurbani from AT&T; R. Even from Gesher Erove; H. Song, Y, Gu, Lucy Yong from Huawei; H. Zhang from NEC Labs, USA; C. Schmidt and L. Xiao from NSN; C. Williams from ZTE; V. Pasual from Tekelec; X. Zhang from PPlive; H. Deng from China Mobile; and J. Lei from Univ. of Goettingen. Zhang, et al. Expires April 23, 2010 [Page 16] Internet-Draft PPSP PS October 2009 10. References 10.1. Normative References [ID.ietf-p2psip-base] Jennings, C., Lowekamp, B., Rescorla, E., Baset, S., and H. Schulzrinne, "REsource LOcation And Discovery (RELOAD)Base Protocol", draft-ietf-p2psip-base-02. 10.2. Informative References [Cisco] Approaching the Zettabyte Era by Cisco. [PPLive] www.pplive.com [PPStream] www.ppstream.com [UUSee] www.uusee.com [youtube] www.youtube.com [tudou] www.tudou.com [CNN] www.cnn.com [Octoshape] www.octoshape.com [ATT] http://mobile.sooyuu.com/Article/content/200905/ 217315094629281_1.shtml [Sigcomm:P2P streaming] Challenges, Design and Analysis of a Large- scale P2P-VoD System,Yan Huang et al, Sigcomm08. [draft-marocco-alto-problem-statement-03] Application-Layer Traffic Optimization (ALTO) Problem Statement, E. Marocco et al, draft-marocco-alto-problem-statement-03 [Pando] www.pando.com [CoolStreaming] CoolStreaming/DONet: A Data-Driven Overlay Network for Efficient Live Media Streaming, Xinyan Zhang et al, [HPTP] HPTP: Relieving the Tension between ISPs and P2P, Guobin Shen et al, [draft-zhang-ppsp-protocol-comparison-measurement-00] www.ietf.org/ internet-drafts/ draft-zhang-ppsp-protocol-comparison-measurement-00.txt Zhang, et al. Expires April 23, 2010 [Page 17] Internet-Draft PPSP PS October 2009 [GENI] www.geni.net [FIND] www.nets-find.net [draft-zhang-ppsp-dsn-introduction-00] www.ietf.org/internet-draft/draft-zhang-ppsp-dsn-introduction-00.txt [MobileTV] MobileTV,Turning in or switching off, Arthur D. Little [Computer Networks:Traffic] Traffic analysis of peer-to-peer IPTV communities, Thomas Silverston et al, Computer Networks, 53 (2009) 470-484 [Survey] A survey on peer-to-peer video streaming systems Yong Liu et al, Peer-to-Peer Netw Appl (2008) 1:18-28,Springer. [draft-zhang-alto-traceroute-00] www.ietf.org/internet-draft/draft-zhang-alto-traceroute-00.txt [P2PStreamingSurvey] Zong, N. and X. Jiang, "Survey of P2P Streaming", IETF PPSP BoF, November 2008. [Challenge] Peer-to-Peer Live Video Streaming on the Internet: Issues, Existing Approaches, and Challenges, Bo Li et al, IEEE Communications Magazine, June 2007(94-99). [CDN+P2P] Efficient Large-scale Content Distribution with Combination of CDN and P2P Networks,Hai Jiang et al,International Journal of Hybrid Information Technology, Vol.2, No.2, April, 2009. [Peering CDN] A Case for Peering of Content Delivery Networks, Rajkumar Buyya1 et al, http://dsonline.computer.org/portal/site/ dsonline/menuitem.9ed3d9924aeb0dcd82ccc6716bbe36ec/index.jsp? & pName=dso_level1&path=dsonline/2006/ 10&file=o10003.xml&xsl=article.xsl& [P2broadcast] P2broadcast: a hierarchical clustering live video streaming system for P2P networks, De-kai Liu et al,International Journal of Communication Systems,Volume 19,Issue 6. [Hybrid] Hybrid Overlay Networks Management for Real-Time Multimedia Streaming over P2P Networks, Mubashar Mushtaq et al, Lecture Notes in Computer Science, Volume 4787/2007. [AHLSS] AHLSS: A Hierarchical, Adaptive, Extendable P2P Live Streaming System, Runzhi Li et al, International Journal of Distributed Sensor Networks, Volume 5, Issue 1 January 2009. Zhang, et al. Expires April 23, 2010 [Page 18] Internet-Draft PPSP PS October 2009 Authors' Addresses Yunfei Zhang China Mobile Email: zhangyunfei@chinamobile.com Ning Zong Huawei Technologies Email: zongning@huawei.com Gonzalo Camarillo Ericsson Email: Gonzalo.Camarillo@ericsson.com James Seng PPLive Email: james.seng@pplive.com Richard Yang Yale University Email: yry@cs.yale.edu Zhang, et al. Expires April 23, 2010 [Page 19]