| 摘要: | Internet在全球的快速發展與廣泛使用，自一九八九年起，其節點數目以每56週增加一倍的速度連續成長，WWW伺服器在近三年更以每23週增加一倍的速度快速增加。因此，Internet的交通流量爆炸增加，現今平均封包長度大約為2000位元，這大多來自WWW相關多媒體的封包，如影像、聲音、視訊等，就目前整體Internet的效能評估，路由器是最主要的瓶頸。另外，無線通訊網路近幾年發展非常迅速，而其「可移動」特性所引發的「重新路由」問題，更是設計開發下一代高效率寬頻路由器必須考慮的重要關鍵。 目前MPEG規格是影像、視訊、與聲音的全世界最重要標準，隨著其全面應用的多樣化，MPEG標準已從最初的MPEG-1改進到MPEG-4，而MPEG-4的物件導向化觀念，在現今網路軟體作業平台環境與物件導向程式語言的發展趨勢配合下，對於未來的即時多媒體應用，將扮演絕對重要的角色，因為無論影像、視訊、或聲音等，當其物件化後，在Internet的服務品質(Quality of Service：QoS)將可獲得更進一步的控制與改善。 為確保多媒體視訊可在Internet上得到最佳的服務品質，主要在以ATM Switch為基礎的下一代路由器架構使用RSVP通訊協定確保其保證頻寬，它是一連接導向為主的架構，最主要的優點是只要虛擬路徑及通道一旦建立，便不需對每個封包進行Routing，所以傳輸速度較快，但也相對產生缺點，因為此種傳輸方式需要某種程度保留路由器的傳輸資源，所以，若有某些通道或路徑保留了某些傳輸資源，卻無法充份利用，則會形成另一種資源浪費。在上述MPEG-4標準提出後，將更突顯此一情況，因為目前各視訊、影像的顯示系統不盡相同，聲音的播放系統也不盡相同，隨著『隨選視訊』(VOD)在近幾年逐漸受到重視，這也意味著多媒體應用的多重傳播功能將在未來的多媒體導向的Internet上扮演關鍵性角色，而這也愈加暴露RSVP在這方面的不足。 另外，由於無線通訊網路的日益普及，可移動式終端系統如Notebook、PDA與行動電話等的普遍使用。隨著可用頻寬在無線通訊網路上的快速成長，多媒體在無線通訊網路上的傳輸也將在未來網際網路上扮演不可或缺的角色，同樣的，RSVP在這方面的缺乏與不足也更將捉襟見肘。 在傳統有線網路的發展上，近幾年Label Switching技術愈來愈受到重視，而這也將在未來路由器設計上扮演重要的角色，所以本研究所提出的各種解決方法也將完全適用於此一架構。 由以上所述可知，本研究將從介質存取控制協定、無線通訊網路的支援、多媒體標準格式、保證服務品質與改善路由策略等五大方向描繪未來多媒體導向的寛頻路由器架構設計與分析。首先，本研究將提出一個無碰撞式的MAC通訊協定，以進一步加速無線通訊網路上的效能。其次，利用Flow與MPEG特性，本研究發展許多更快速的路由策略以加速多媒體封包在實際網路上的效能。第三，本研究將設計並發展一嶄新的動態(Dynamic) RSVP通訊協定(DRSVP)，以達成下列目標： 1. 對不同的終端系統分別提供足夠的解析度。2. 有效控制網路上的封包大小及交通流量，使所保留的網路資源可以完全利用。3. 當路由器發生過度擁塞，所保留的資源通道與路徑可以適當的加以調整。除此之外，DRSVP也特別著重支援無線通訊網路與有線網路上Label Switching技術的支援。 最後，由於目前網路網路上路由器的路由方式可分為兩大類，一為連結導向的路由器，一為非連結導向的路由器，前者適用於大流量的資料傳送，如多媒體應用服務等，而後者則適用於小流量的資料傳送，如ICMP等。本研究將提出一模組化的新代寬頻路由器架構，以模組方式結合連結導向模組與非連結導向模組的優點，並對其效能進行分析與評估，進一步勾勒未來整合各網路應用服務特性的路由器架構。 Currently, the Internet is widely used and growing rapidly. The number of its hosts has doubled approximately every 56 weeks since 1989; the number of its WWW servers has doubled every 23 weeks for the last three years. Especially, the traffic on Internet is much busier than before. Measurement indicates that the average packet size is 2000 bytes, approximately. Most of the traffics are from multimedia application services, such as audio, video and etc. Because the bottleneck of overall Internet performance is the router, it’s very important to study and design the so-called next-generation broadband switching router. MPEG is the international standard of image, video and audio. Its evolution is from MPEG-1 to MPEG-4. The object-oriented concept is a critical characteristic of MPEG-4, which can benefit software operating environment, object-oriented programming language and real-time multimedia applications. In order to obtain better or acceptable QoS of multimedia services in the future multimedia-oriented Internet, it might be the best approach at this moment to use RSVP in the router. The advantage of this approach is that no routing action is needed for every packet after the virtual path and virtual channel are established. Due to bandwidth control, the QoS of multimedia services can be better. However, because some resources of the router are reserved, it might have some resources not fully utilized. If MPEG-4 is used, the situation can be improved. Because the end systems of multimedia services might be different from one another, the guaranteed bandwidth for transmitting necessary information volume are different. This study will design a new Dynamic RSVP (DRSVP) protocol for achiving better QoS by using MPEG-4. In addition, due to the importance of wireless communications networks and mobile computing systems, many portable devices, such as notebook, PDA, mobile phone and etc., are widely used. Because the available bandwidth grows rapidly in the wireless communication network, multimedia application services play indispensable roles in the future Internet. Simultaneously, RSVP runs short of ways in dealing with the support in the wireless communication network. The Label Switching Technology attracts many attentions in the conventional wired network, currently. So, it’s important that every solution proposed in this study is suitable to this architecture. As described above, this study describes the next-generation broadband switching systems router architecture from five categories: MAC protocol, wireless communication support, multimedia format, guaranteed QoS and improving routing strategy. At first, this study proposes a collision-free MAC protocol to improve the routing efficiency in the wireless communication network. Then, using the characteristics of flow and MPEG, this study proposes several more efficient and rapider routing strategies. Third, this study designs and develops an all-new resource reservation protocol — Dynamic RSVP (DRSVP) to achieve the following goals. 1. Provide different necessary resolutions for different end systems. 2. Efficient control the traffics on Internet to fully utilize the reserved resources and bandwidth. 3. The reserved resources can be dynamically adjusted when congestion occurs. Especially, DRSVP emphasizes the support for the wireless communication network and the Label Switching technology in the wired network. Finally, the current routing methods are classified into the connection-oriented switch and connectionless router. The former is suitable for the great quantity transmission of traffics, such as multimedia. And, the latter is suitable for the small-scale traffics, such as ICMP. Combining the advantages of the above two methods, this study proposes modularized router architecture to plot the next-generation broadband switching router systems architecture in future Internet. |
