SIP建構於非結構性點對點網路之研究

Abstract

SIP (Session Initiation Protocol) 已被廣泛使用在建立基於IP的多媒體通訊連線。然而客戶-伺服器架構的SIP卻使得使用者遭受網路瓶頸和單點錯誤的風險。點對點網路架構的SIP隨即被提出，由於點對點的網路取代中央伺服器的設計，故具有延展性及可靠性的優點。其中，基於DHT架構的Chord方法廣受歡迎而被採納使用於建立邏輯層網路並支援使用者註冊及電話連接。基於點對點的網路設施，使用者可以用Chord提供的搜尋機制來連接SIP電話連線。 然而，先前的研究並未考慮到行動性的問題，這是在行動網路上不可或缺的重要性質。在具有行動使用者的DHT架構點對點網路中，它會使系統產生額外的電話連線延遲，並且還需要耗費嚴重的維繫費用來確保Chord網路在行動環境下的正確性。 在這篇論文中，我們建議使用非結構性的點對點網路來作為SIP的平台，另外每個節點使用與其具有關係的節點作為鄰近節點，因此節點可以更容易地找到朋友在點對點網路上的所在位置，並可快速開啟電話連線。最後我們比較我們提出的解決方案與建構於Chord的SIP方案，証明我們的方法耗費更少的維繫費用而且比先前的方法有更高的系統效能。

SIP (Session Initiation Protocol) has been widely used for call setup of IP-based multimedia communications. The client-server architecture of SIP, however, exposes users in the risk of bottleneck and single point failure. P2P (Peer to Peer) SIP is consequently proposed with the advantages of scalability and reliability by replacing centralized servers with a self-organizing P2P network. In which, DHT-based Chord approach is attractively used to build the logical overlay and supports registrations and call setup. Based on the P2P infrastructure, users can initiate an SIP call by invoking a process of user look-up in a Chord ring. However, previous studies did not consider the mobility issue which is an essential property in mobile Internet, and extra call setup latency is introduced while there are some roaming nodes in a DHT-based P2P network. Also, a DHT-based P2P network needs to spend heavy maintenance efforts to ensure the correctness of a Chord ring in a mobile environment. In this thesis, we suggest an unstructured P2P network for P2P SIP in which nodes establish neighbor links based on their relationships. Therefore, nodes can easily locate their friends in a P2P network and quickly initiate an SIP call. In the end, we compare the proposed solution with the P2P SIP over Chord, and demonstrate that our method requires less maintenance effort while better system performance can be achieved than the previous approach.