Ning Zong, Huawei Technologies Yunfei Zhang, China Mobile Communication Corporation

1. PPSP BAR BOF meeting74th IETF – San Francisco, CA, USAMarch, 2009P2P Streaming Protocol (PPSP) Requirements Ning Zong, Huawei Technologies Yunfei Zhang, China Mobile Communication Corporation Victor Pascual, Tekelec

2. Motivation for PPSP • P2P streaming applications have become more and more popular on Internet due to the advantages of reduced server cost and better scalability of system dimensions • An open and standardized protocol for P2P streaming would greatly benefit many applications (e.g. web services, IPTV, content distribution network) through re-use of a common P2P architecture and flows to share capabilities (e.g. storage, computation) with each other. • More detailed motivations are described in Problem Statement of P2P Streaming Protocol (PPSP).

3. Legend Content Registration and/or Peer List Request PPSP Signaling PPSP Transmission Scope of PPSP – what PPSP does Tracker Request “Star Wars” and return A/B/C Register “Star Wars” Chunk Description, Peer List, Peer Status, etc. A B Chunk Data requestor C • The basic role of PPSP is to define a protocol of locating and transmitting real-time data efficiently from multiple sources with different pieces in P2P environment.

4. General (Architecture) Requirements • PPSP MUST be able to support streaming services when the number of users keeps growing. - Content is shared among peers, thus reducing the burden on servers. • PPSP MUST be self-adaptive to support a large number of dynamically joining and leaving users. - Peers contact more than one peer simultaneously to share content, thus reducing the impact of peer churn. Data Sharing

5. Signaling Requirements • PPSP signaling MUST support to carry chunk description of peers. - To share content, peers share information on which chunks are on which peers. A common chunk description called Bit Map is described in draft-zong-ppsp-req-00.txt. • PPSP signaling MUST support to negotiate the meaning of chunk description, e.g. chunk is segmented based on content size or length, if based on size, then the unit is KB or Byte. - It is useful to apply such negotiation to allow for more flexible interaction between different applications. E.g. some P2P streaming applications are based on chunks with size of KB while others are based on size of Byte. Negotiate Chunk Description Chunk Description

6. Signaling Requirements (Cont.) • PPSP signaling MUST support to carry additional peer list. - Peers need to learn about other peers by sharing and aggregating their peer lists with information from other peers. • PPSP signaling MUST support to carry peer status for content sharing (e.g. peer bandwidth, workload). - With this peer status information, a peer can select more appropriate peers for content sharing based on some content sharing strategies and/or application requirements. Additional Peer List Peer Status

7. Transmission Requirements • PPSP transmission MUST be able to support limited start-up delay and limited latency between the broadcasting time and the audience view time. • PPSP transmission MAY support efficient one-to-many data transport with some attempt at fairness assurance and balance between self-constraint and aggression for network bandwidth. • More transmission requirements are to be studied …

8. Error Handling and Security • A peer MUST be able to respond with error information to peers sending chunk description messages when some information (e.g. chunk ID) cannot be understood in the message. • PPSP MUST be able to provide mechanisms to prevent peers from distributing wrong information, such as claiming they have the chunks that they don't, or sending out false peer status information. • More error handling and security requirements are to be studied …

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