由於掌上型電腦(PDA)和筆記型電腦的快速成長，無線網路對現今之電腦及通訊業而言，成為一項極重要的觀念及技術。而Ad hoc networks是一種完全經由無線連結的行動節點所建構而成，是無基礎建設(infrastructureless)及無集中式管理的無線網路，主要提供不限量的用戶，能隨時架設無線通訊網路，每個節點都具備繞送(routing)的功能，並且能尋找(discovery)和維護(maintenance)這繞送資訊。但移動的節點會改變網路的拓撲，因此要選擇一適合的繞徑協定(routing protocol)，來為移動的節點尋找一溝通的路徑。由此可知，繞徑協定扮演一個很重要的角色。

　　近年來，有許多學者致力於研究Ad hoc networks的繞徑協定，如AODV、DSR等皆是。另外，在其中考量備份繞徑(backup route)與多重繞徑(multiple route)的方法也陸續被提出。
虛擬區域網路﹝virtual LAN; VLAN﹞最重要的特性之一是能藉由虛

　　擬區域網路橋接器﹝VLAN bridge﹞將分屬不同實體網段的工作站設定成同屬單一廣播領域﹝broadcast domain﹞、易於管理之邏輯群組。其次，虛擬區域網路間之傳輸則被加以過濾以舒緩因廣播封包氾濫所造成之都會網路擁塞現象。因擁有上述特性，虛擬區域網路在網路頻寬極為有限、且移動性工作站﹝mobile stations﹞之位置又經常變化的無線網路環境﹝wireless environment﹞下相當具有發展潛力。

　　本論文之研究重點乃是將多重跳接式無線網路（multihop wireless networks）技術與虛擬區域網路相結合以創造出multihop Mobile Virtual LAN (MVLAN)的網路環境。在本論文中，我們提出一具高效能且支援VLAN的無線網路擷取點（VLAN support Access Point; VSAP）的系統架構及其所需之相關通信協定之設計包括成員追蹤協定（member tracking protocol）與訊框前送協定（Frame forwarding protocol）。透過成員追蹤協定的設計，移動性工作站一旦註冊成為某特定VLAN成員後，其廣播領域將仍以涵蓋整個VLAN的範圍為限，而不因其所在位置不同而改變。一方面MVLAN的技術將使有線及無線網路頻寬獲得有效利用；另一方面，藉由multi-hop的技術可將MVLAN的範圍拓展到通信基礎設施不足、或因天災導致斷訊的區域以創造出隨時隨地通訊無阻的資訊網路。

　　Ad hoc networks are constructed by mobile nodes with wireless connections – that is a wireless network without infrastructure or centralized management. Mainly﹐it provides limitless users with the ability to construct wireless networks at any time. Every node has routing capabilities﹐with the ability to discover and maintain routing information. Since the networks topology may be changed by the mobile nodes﹐selecting an appropriate routing protocol is crucial to find a communications route for the mobile node. Thus﹐routing protocols take on an important role.

　　Many researchers have devoted to develope routing protocols in ad hoc networks with limited bandwidth. Besides﹐the consideration of backup routes and multiple routes have been also proposed.

　　One of the most attractive features of the virtual local area network (VLAN) is the capability to group users from different physical LAN segments into a single broadcast domain. VLANs﹐thus﹐facilitate easy administration of logical groups of stations that can communicate as if they were on the same LAN. In addition﹐Traffic between VLANs is restricted. This in turn limits the propagation of multicast and broadcast traffic between VLANs. These two features make the VLAN more rewarding in a wireless environment where the bandwidth is quite limited and constant moving of the mobile stations are highly anticipated.

　　In this thesis﹐we explore the possibility of combining the concept of multi-hop wireless technique with the VLAN to extend the VLAN scope toward the always on” network environment﹐including area where there is little/no communication infrastructure﹐or the existing infrastructure is damaged after a hurricane or earthquake. For supporting such an integration of ad hoc networks with Mobile VLAN (MVLAN)﹐we present in this paper the design of multi-hop MVLAN member tracking mechanism and the frame forwarding protocol. In summary﹐the achievement of multi-hop MVLAN is twofold. First﹐through the MVLAN technique﹐the transparent handoff of mobile stations can be achieved and the network bandwidth can be efficiently and effectively utilized. Second﹐through the ad hoc networking technique﹐the VLAN scope can be scaled to include areas where the communication infrastructure is insufficient.

〔1〕B. Li and P. Vankwikelberge, “Virtual LAN (VLAN) Configuration and Address Resolution in an ATM Network,” 2nd Int’l Symp. On Interworking (INTERWORKING’94), Sophia Antipolis, May 1994, pp. 179-190.

〔2〕IEEE Draft Standard for Traffic Class and Dynamic Multicast Filtering Service in Bridged Local Area Networks, P802.1P/D2 Feb. 18, 1996

〔3〕N. F. Huang, Y. T. Wang, B. Li and T. L. Liu, “Mobility Management of Interconnected Virtual LANs over ATM Networks,” IEEE GLOBECOM, Nov. 1996, pp. 1156-1161.

〔4〕IEEE Draft Standard for Virtual Bridged Local Area Networks, 802.1Q/D11 July.30, 1998.

〔5〕C. E. Perkins and E. M. Royer. Ad hoc On-Demand Distance Vector Routing. Proceedings of the 2nd IEEE Workshop on Mobile Computing Systems and Applications, 1999.

〔6〕T. Miyagi, M. Iizuka, M. Morikura, “A novel route reconstruction practically for P-MP communication over wireless ad-hoc network,” Proc. Vehicular Technology Conference. vol. 2, pp. 1522-1526, 2000.
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〔7〕S. H. Bae, S.-J. Lee, W. Su, M. Gerla, “The design, implementation, and performance evaluation of the on-demand multicast routing protocol in multihop wireless networks,” IEEE Network, vol. 14 Issue: 1, pp. 70-77, Jan.-Feb. 2000.

〔8〕C. E. Perkins, E. M. Royer. Multicast Ad hoc On-Demand Distance Vector (MAODV) Routing. IETF Internet-draft, 2000, http://www.ietf.org/internetdrafts/draft-ietf-manet-maodv00.txt

〔9〕S. Basagni, D. Turgut, S.K. Das, “Mobility-adaptive protocols for managing large ad hoc networks,” IEEE International Conference on Communications ICC 2001, vol. 5, pp. 1539-1543, 2001.

〔10〕C. M. Chung, Y. H. Wang, and C. C. Chuang, Ad Hoc On-
Demand Backup Node Setup Routing Protocol, Proceedings of the 15th IEEE International Information Networking Conference, 2001.

〔11〕M. Gunes, U. Sorges, and I. Bouazizi. ARA - The Ant-Colony Based Routing Algorithm for MANETs. Proceedings of International Conference on Parallel Processing Workshops (ICPPW'02), 2001.

〔12〕S. Guo, O. W. Yang. Performance of Backup Source Routing (BSR) in mobile ad hoc networks. IEEE Wireless Networking Conference, 2002.
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