| 摘要註: |
以SIP為基礎協定的VOIP架構中，點對點傳輸是最為理想，也是對伺服器負擔最輕的傳輸方式，但點對點傳輸卻無法穿越防火牆或是NAT，這時必須依靠主從式架構傳輸模式來解決這樣子的問題。然而主從式傳輸模式會隨著使用者的增加，使得伺服器的負擔也隨之增加，因此整合點對點與主從式傳輸模式，可以減輕伺服器的負擔，也可以讓傳輸變的更有效率。本研究不僅提出了一種多從伺服器的架構系統，來達到負載平衡以及系統整合，也更近一步的研究與討論到，取用何種負載演算法，作為規則分配給叢集式架構系統中的伺服器群。研究平衡負載方式分為兩階段，第一階段是依使用者所處的網路環境，動態選擇兩種傳輸模式，當沒有NAT或是防火強時,就會取用點對點模式傳輸以減少負擔，反之則選擇主從式模式作為傳輸方式，並且將在主從式架構模式下的叢集伺服器群作分類，各類組群僅提供單一服務，以此方式達到負載平衡。第二階段則是研究如何配之群組的工作，以何種負載平衡演算法去做分配。負載平衡演算法方式大致可以區分成兩大類，一種是靜態分配，而另一種是動態分配。各有其優缺點，比如說，靜態分配有低成本以及速度快的優勢。而動態分配具有準確分配的優勢。若各取其優勢來做分配的規則，我們便可以以既快速又準確的方式來做負載平衡的分配，並且是在更具有保障的情況下，把工作分配給較適合的伺服器去做處理。要做負載平衡，大多主要關注伺服器的中央處理機[1][2][3]和記憶體[4]的使用率，但在我們的電信環境裡，我們多考慮一項因子，那就是通話的連線數量，在多考慮了這個參數的情況之下，我們不僅了解到當下的連線數量，也知道連線種類是屬於什麼，比方說，多少通語音以及多少通影音。有了這些資訊，我們便可以估計系統還剩下多少資源以及能力，當需要的時候，將可以拒絕接受新進的工作。經過以上的改善以及決策，我們可以預估，負載平衡的分配將會更準確以及恰當。 Under a SIP based VOIP system, peer to peer mode is the desired operation mode, not only the load of the network can be reduced, but also the transmission quality will be better. But peer to peer mode isn’t capable to pass through firewall or NAT, if there’s any end user behind firewall or NAT, client server mode need to be used to solve such problem. But in client server mode, the load will increase with the raise of the user, in order for the VOIP system to operate efficiently, it is best to keep the system in peer to peer mode. In our theme, we provided a two stage way to reduce and distribute the system load. First stage is the combination of the transmission mode that mentioned above. The master will directly use peer to peer mode for transmission to reduce the network load, when a service that does not need client server operation, If the service requires operating in client server mode, the system will change transmission mode automatically. Furthermore, the multi-servers that are used under client server mode will be divided into different groups, each group provides only one service, so the load can be distributed by different services. Second stage is the way to distribute the load to an appropriate server that is under client server mode. Furthermore, to provide an efficient result, what kind of load balance algorithm should be used? Load balance techniques are mainly concerned about the use of two main resources, namely CPU [1][2][3] and Memory [4], but in our telecommunication environment, we considered an addition parameter, the connection of the phone number/codec, with this addition consideration, we not only knowing the number of the established connections, but also been notified what kind of connection is connect, for example, the connection number of video or audio calls, with such information, the system will be able to evaluate the remaining resource, and refuse incoming calls when needed, in such condition, balancing the load of the server will be more efficient and accurate. |