具Relay的P2P網路電話分析

Analysis of P2P VoIP with Relay

賴正昌(Jeng-Chang Lai)

指導教授 ： 趙燿庚

元智大學/電機通訊學院/通訊工程學系/碩士(2008年)

https://doi.org/10.6838/YZU.2008.00239

摘要

NAT(network address translator)普遍用來解決IPv4位址不夠的問題，但它卻阻礙了Internet網路上點對點(Peer-to-Peer)直接傳輸，尤其是現在已經被廣泛使用的網路電話，NAT經常阻礙網路電話成功建立P2P連線。許多研究已經提出各種網路電話穿越NAT的方法，經常被討論的是一個端點穿越NAT的問題，而建立網路電話通訊，至少是兩的端點建立連線，如果只有單邊成功穿越NAT，這個連線將不能被建立，不能被建立的端點，只能選擇轉送（Relay）和伺服器通訊，比如遇到Symmetric NAT只能解決方法是利用轉送，轉送封包建立的連線造成伺服器的負擔，也浪費頻寬資源。

本論文討論到即使是遇到Symmetric NAT，還是有進行P2P連線的機會。這個想法是，把原本解決SIP穿越NAT的方法中的STUN和TURN同時使用，加上UDP穿越NAT的技術。結果說明了這個的方法可以提高建立P2P連線的成功率。

關鍵字

網路電話 ； 點對點 ； 轉送

並列摘要

Network Address Translator (NAT), which is used to extend the IPv4 address space, may break Peer-to-Peer connection. Many researches have discussed that NAT often hinder the establishment of P2P connection, especially for Symmetric NAT. And we know to establish telephony connections at least two of the endpoint. P2P VoIP is no exception. If make establishment P2P fail, general used method is to choose relay method, which communicates with server and then server goes to communicate with another endpoint. This will build the indirect communication between two endpoints. However relay method brings heavy loading on server and wastes bandwidth at the same time.
In the thesis, we observe even if symmetric NAT, there is still a P2P connection opportunity. The idea is to combine original methods, which traverses NAT in the use of STUN and TURN at the same time, with UDP through NAT technology. The result shows that our method can increase P2P connection success probability.

並列關鍵字

P2P ； VoIP ； Relay ； NAT

參考文獻

[9] 張澍元, “探討SIP 通過防火牆與網路位置轉換的方法”, 電腦與通訊雜誌, 第105 期, 2003 九月.

Session Initiation Protocol”, Internet Engineering Task Force RFC 2543, June

User Datagram Protocol (UDP) Through Network Address Translators (NATs)”,

[6] B. Goode, “Voice over Internet Protocol(VoIP)” Proceeding of the IEEE,

May 1994.