Distributed Differentiated Service for Ad-hoc Networks

[[abstract]]近年來，無線隨意網路的應用已漸漸普及，由於無線隨意網路俱有分散式環境的特質，使得無線隨意網路可以即時地調整其規模而毋須仰賴任何中央控管的機制。但是在缺乏服務品質保證之環境下，容易造成資源及頻寬的分配不均，使得各種應用服務難已達成。為了在無線隨意網路下達成服務品質之目標，差異性服務 (DiffServ) 針對不同應用之特性加以分類以決定優先權，但在分散式的環境下運作必須修改其架構以符合其環境特性。在此我們提出了動態網路環境下之分散式差異性服務，架構中，我們擴展了繞徑協定之用途，並針對封包之特性及資源需求決定優先權。在ns-2環境下模擬，結果顯示分散式差異性服務模型可以有效地控制交通流量並降低節點壅塞的情形發生。[[abstract]]Ad-hoc networking has been of increasing interest in recent years. Due to the nature of Ad-hoc networks, the distributed approach allows each network to adjust in size or fragment in real-time without any central administrator. But the lack of service guarantees becomes the significant barriers for various applications. To facilitate end-to-end Quality of Service over Ad-hoc networks, differentiated services (DiffServ) that provide aggregated classes of services may be a possible solution but necessitates some adaptation suitable within distributed environment. This paper presents an approach to supporting distributed Quality of Service (QoS) in dynamic network environment. With this approach, we propose an extended routing protocol for ad hoc networks and the mechanism based on priority of packet. We have implemented this algorithm in ns-2. Simulation results indicate that the distributed differentiated service model can smooth the traffic, thus reduce the traffic peaks that cause congestion. For real-time applications, one of the most interesting parameters is delay jitter. When the CBR stream is shaped and marked using srTCM, the results show that the delay jitter achieves the basic requirements of VoIP