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1、西安邮电学院西安邮电学院 毕毕 业业 设设 计（译计（译 文）文） 论文题目：论文题目： P2P 技术在多媒体服务中的应用研究技术在多媒体服务中的应用研究 院院 （系）：（系）： 通信与信息工程学院通信与信息工程学院 专专 业：业： 通通 信信 工工 程程 班班 级：级： 通工通工 班班 学生姓名：学生姓名： 导师姓名：导师姓名： 职称：职称： 工程师工程师 DIRECTORY PEER-TO-PEER (P2P) COMMUNICATION ACROSS MIDDLE- BOXES.1 3.1 RELAYING.1 3.2 CONNECTION REVERSAL.1 3.3 UDP HOLE
2、 PUNCHING.3 3.3.1 PEERS BEHIND DIFFERENT NATS.3 3.3.2 PEERS BEHIND THE SAME NAT.5 3.3.3 PEERS SEPARATED BY MULTIPLE NATS.6 3.3.4 CONSISTENT PORT BINDINGS.7 3.4 UDP PORT NUMBER PREDICTION.7 3.5 SIMULTANEOUS TCP OPEN.9 目录目录 利用代理服务器的 P2P 通信.1 3.1 转发 .1 3.2 反向连接 .1 3.3 UDP 打洞技术 .2 3.3.1 处于不同 NAT 之后的客户端通
3、信 .2 3.3.2 客户端都处于相同的 NAT 之后 .3 3.3.3 客户端分别处于多层 NAT 之后 .4 3.3.4 保持端口绑定 .5 3.4 UPD 端口号预言 .5 3.5 同时开放 TCP 连接.6 Peer-to-Peer (P2P) communication across middle-boxes Techniques for P2P Communication over middle-boxes This section reviews in detail the currently known techniques for implementing peer-to-
4、peer communication over existing middle boxes, from the perspective of the application or protocol designer. 3.13.1 RelayingRelaying The most reliable, but least efficient, method of implementing peer-to-peer communication in the presence of a middle-box is to make the peer-to-peer communication loo
5、k to the network like client/server communication through relaying. For example, suppose two client hosts, A and B, have each initiated TCP or UDP connections with a well- known server S having a permanent IP address. The clients reside on separate private networks, however, and their respective mid
6、dle boxes prevent either client from directly initiating a connection to the other(as in FIG 1-1). FIG 1-1 Server Relaying Instead of attempting a direct connection, the two clients can simply use the server S to relay messages between them. For example, to send a message to client Peer-to-Peer (P2P
7、) communication across middle-boxes 1 B, client A simply sends the message to server S along its already-established client/server connection, and server S then sends the message on to client B using its existing client/server connection with B. This method has the advantage that it will always work
8、 as long as both clients have connectivity to the server. Its obvious disadvantages are that it consumes the servers processing power and network bandwidth unnecessarily, and communication latency between the two clients is likely to be increased even if the server is well- connected. The TURN proto
9、col TURN defines a method of implementing relaying in a relatively secure fashion. 3.23.2 ConnectionConnection reversalreversal The second technique works if only one of the clients is behind a middle box. For example, suppose client A is behind a NAT but client B has a globally routable IP address,
10、 as in the FIG1-2: FIG 1-2 Connection reversal Client A has private IP address 10.0.0.1, and the application is using TCP port 1234.This client has established a connection with server S at public IP address 18.181.0.31 and port 1235.NAT A has assigned TCP port 62000, at its own public IP address 15
11、5.99.25.11, to serve as the temporary public endpoint address for As session with S: therefore, server S believes that client A is at IP address 155.99.25.11 using port 62000. Client B, however, has its own permanent IP address, 138.76.29.7, and the peer-to-peer application on B is accepting TCP connections at port 1234. Now suppose client B would like to initiate a peer-to-peer communication session with client A. B might first attempt to contact client A either at the address client A believes itself to have, namely 10.0.0.1:1234, or at the address
