| 摘要: | 近年來，隨著網際網路迅速發展及光纖網路的普及，使用者可從網路上獲得許多資訊及服務，尤其對多媒體服務的需求大幅增加，如：隨選視訊(VOD，Video On Demand)、網路電話(VoIP，Voice Over Internet Protocol)、YouTube、網路電視、線上遊戲等。因而對網路頻寬的使用量與日俱增，如果在現有的企業網路架構下，未能提供較佳的網路服務品質及頻寬管理，並且優化傳輸的效率，這將會使得企業服務成本增加，也將使得提供的服務品質大打折扣，因而流失大量的客戶群造成企業的損失。
然而企業對大幅增加的頻寬需求及提供多樣化的服務給使用者，往往為了節省成本，只願意投入成本在開發網路服務，再將此網路服務加入到原有的企業網路中，常忽略掉原先的資訊基礎架構早已超出負載，最後導致企業服務中斷，嚴重者，有可能會讓企業面臨營運的危機。
本論文主要的研究重點在使用NS2網路模擬工具，模擬出企業的網路架構環境，再進行多媒體傳輸品質的模擬測試，分析出此網路架構會面臨的瓶頸，並提出QoS管理機制，透過此機制能使優先等級較高的封包獲得較高的優先順序，最後提出有效的改善方案及預估改善後的網路服務品質，其使企業能得到較高的服務效能。
Recent years, with the rapid development of Internet and the popularity of fiber-optic network, the users can easily obtain a lot of information and services from the Internet. In particular, the demand for multimedia services such as Video On Demand (VOD), Voice Over Internet Protocol (VoIP), YouTube, Internet TV, on-line games and so on, has increased substantially. Therefore, the demand for the network bandwidth is increasing dramatically. If the existing enterprise network infrastructure does not provide better quality of network service and bandwidth management, and optimize the efficiency of the transmission, which will increase the cost of corporate services and reduce the quality of service, then the loss of a large number of customers results in business loss.
However, to meet the substantial increase in bandwidth requirements and diversity services, the corporate is barely willing to invest in developing Internet services, which is added into an existing network in order to save costs. By doing so, the original designed maximum capacity might be overused and lead to the corporate service interruptions. In severe case, this may face business crisis.
This thesis focuses on using NS2, a network simulation tool, to simulate a particular corporate network environment and test the quality of multimedia data transmission. Based on the simulation results, the potential bottleneck of this network will be found and a QoS management mechanism will be proposed. Through this control mechanism, the higher priority packets will be guaranteed to get a better performance in data flow. Finally, this thesis proposes an effective improvement plan and shows the estimated quality of service over improved network, which will benefit the corporate to provide higher service level. |
