無線網格計算環境下之網路層資源監測及發現服務

Abstract

在網格計算的領域中，網格資訊服務在網格資源的發現、註冊以及索引等功能上，扮演一個相當重要的角色。網格資訊服務的資源監測及發現服務機制（MDS）提供了一些訊息來獲取資源提供者的狀態資訊，並且持續地進行狀態監測。由於無線環境的特殊性，例如：頻繁的資訊更新、短時效的電源供應以及有限的計算能力等等，有線網格環境的資源監測及發現方法並不能直接適用於無線網格環境。因此，在本論文中，我們提出一個在網路層的監測及發現服務機制（NL-MDS），它是一個將無線網格資訊嵌入無線隨意路由協定的方法。這些資源提供者所擁有的資源種類及狀態資訊都交由AODV路由協定的message extensions來進行載送。如此一來，當使用者有資源需求時，就可以在所提出的資源表中，進行快速的查詢。我們比較了NL-MDS與WGMDS，而WGMDS是Globus Toolkit裡，MDS方法的延伸及改良設計。我們評估的項目為所產生的控制封包數量以及資源發現完成的時間。模擬結果顯示，當網格節點數為10~50，NL-MDS所產生的控制封包數量約較WGMDS減少23% ~ 2%，而資源發現完成的時間也較WGMDS平均減少約50%。因此，在無線網格計算環境下，我們所提出的輕量級資源監測及發現方法可以提供一個快速且低運作成本的資源監測及發現服務，而且非常適用於臨時性質或是緊急需求的無線網格應用。

In grid computing, the grid information service (GIS) plays an important role in grid resource discovery, registry, and indexing. The resource monitoring and discovery service (MDS) in GIS provides a set of messages to get the status information of resource providers and keeps monitoring on them. Traditional resource monitoring and discovery schemes for wired grids are not directly applicable to wireless grids due to the characteristics of them, such as frequent information update, short-lasting power source, and limited computing capacity. In this thesis, we propose a network layer resource monitoring and discovery service (NL-MDS) scheme. It is an ad-hoc routing protocol embedded method for wireless grids. The resource types and status information of resource providers are piggybacked on the message extensions of the ad-hoc on-demand distance vector (AODV) routing protocol. Each client, which needs resources, can perform a fast look-up for resource providers in the proposed resource table. We have compared NL-MDS with WGMDS (Wireless Grid Monitoring and Discovery Service), an extension of MDS in the Globus Toolkit, to evaluate the number of control packets and the discovery completion time. Simulation results show for nodes from 10 to 50, NL-MDS can reduce the number of control packets from 23% to 2%, and decrease the discovery completion time on average by 50% compared to WGMDS. Therefore, the proposed lightweight resource monitoring and discovery scheme can support a fast resource monitoring and discovery service with low overhead on wireless grids, and is suitable for wireless grids in temporary or urgent needs.