適用於可信賴 SIP 代理伺服器群之高效率負載平衡策略

Abstract

因為 VoIP 與多媒體服務的興起， SIP 協定被用來為網路使用者建立雙方對談或是多方視訊會議的連線。在建立連線的過程中， SIP 代理伺服器為雙方使用者轉交訊息，故為極重要的角色。隨著 VoIP 及多媒體服務的要求逐漸增加，採用單一 SIP 代理伺服器會產生效能下降及有單一失敗點的問題。為了解決上述的問題，我們設計一個前端為 n + 1個 (n 個使用中與一個備用) 分派器，以控制後端為 m 個 使用中 SIP 代理伺服器群的架構。但是分派器要如何將使用者傳遞過來的訊息平均分配到後端 SIP 代理伺服器群，而不會造成單一 SIP代理伺服器負荷過載或長時間延遲是我們想要解決的問題。在本論文中，我們設計及實作對於 VoIP / 視訊會議等應用提供一個可靠性的SIP群組架構，同時也提出一個基於 OpenAIS 的 SIP 負載平衡策略 (OSLB)，以平衡 SIP 代理伺服器群組間的負載，且當其中一個分配器或是SIP 伺服器當機時，能將造成失敗的連線數減低。實驗的結果顯示OSLB比目前的SIP load balancer方法有相近的負載平衡值(1.05 與 1.04)，但是因為 SIP 代理伺服器當機所造成的失敗連線數較之減少 82%。

Because of the arising of VoIP and multimedia services, the Session Initiation Protocol (SIP) has been used to establish multimedia sessions which could be a simple two-way phone call or a collaborative video conference session between users on the Internet. In the procedure of establishing these sessions, a SIP proxy server plays an important role by forwarding SIP messages between users. Continued growth in VoIP and multimedia usages, using only one SIP proxy server may cause performance degradation, and has a single point of failure issue. In order to solve these problems, we design m active SIP proxy servers as a cluster in the backend, which are controlled by n + 1 dispatchers (n active dispatchers plus one backup dispatcher) in the front end. But how to make a dispatcher distributes requests from users to one of the back-end SIP proxy servers without causing overloading or long delay is the load balancing issue that we also want to resolve. In this thesis, we have designed and implemented a dependable SIP-based clustered architecture for VoIP/Video conferencing applications, and also have proposed an efficient OpenAIS-based SIP Load Balancing strategy (OSLB) that can balance the proxy servers’ load and reduce the number of failed calls when one of the dispatchers or one of the SIP proxy servers crashes Experimental results show that our OSLB is comparable to an existing work, SIP load balancer, in terms of load balance metric (1.05 vs. 1.04). However, our OSLB reduces the number of failed calls when a proxy server failed by 82% compared to the SIP load balancer.