| As the Internet becomes more and more popular, the demand on Quality of Service (QoS) is increasing rapidly, especially when multimedia traffic emerges over the Internet. In order to provide different levels of services to the customers, a new QoS architecture is required in today's IP networks.; Differentiated Services (Diffserv or DS) architecture has recently become a promising method to address QoS issues in IP networks. It uses the DS field (which was the TOS octet) in the IP header to distinguish QoS requirements of each packet. At the network boundaries, IP packets are classified to a smaller number of aggregated flows, based on setting bits in their DS fields. Within the core of the network, each aggregated flow is forwarded according to a particular forwarding treatment (Per-Hop Behavior or PHB) which is associated with the DS codepoint. This architecture can achieve service discrimination without signaling and per-flow state maintenance within the network core. Thus it greatly reduces the network complexity and overhead, which in turn increases its potential for scalability.; In order to observe the Diffserv behavior, we developed the Queen's University IP Simulator-Version 2 (QUIPS-II), which was written in Java language on a UNIX platform. The simulator is composed of three kinds of modules—the network modules, the control modules, and a graphic user interface. It deploys traffic conditioning functions and three PHBs in the Diffserv environment. Based on QUIPS-II, we evaluated the performance of the three PHBs in terms of packet delay and packet drop rate. A significant amount of results have been obtained under various parameter settings. The results show that the Diffserv mechanisms can effectively differentiate between service levels on the Internet. |
