Multi-Class QoS Routing with Multiple Routing Tables Hedia Kochkar*, Takeshi Ikenaga*, Yoshiaki Hori** and Yuji Oie* * Dept. of Computer Science and Electronics, ** Dept. of Art and Information Design, Kyushu Institute of Technology, Kyushu Institute of Design, Fukuoka, 815-8540, Japan Iizuka, 820-8502, Japan traffic and may also decrease the throughput of the whole network. Abstract— Future communications networks are expected to support applications with quality of service (QOS) requirements. Supporting QoS poses major challenges due to the large size and complex structure of networks. Several studies have addressed different aspects of QoS routing. In this paper, we present a new approach of QoS routing based on the concept of multiple routing tables. Traffic with QoS requirements will have their own routing table. This scheme can prevent such traffic from concentrating on some link, so it can improve their performances. Since the goal of the QoS routing is to find a path that satisfies the given requirements and may increase the global network resource utilization, an efficient QoS routing algorithm in the current IP networks is needed. Depending on the path selection process, an algorithm could either return the best next hop or the path to destination. The first one is the traditional hop-by-hop routing and is referred as Distributed QoS routing. The second is referred as source routing where the entire path computation is done at the source router. From our extensive simulation results, we have found that both packet loss of QoS traffic and throughput of best-effort traffic can be improved by using our scheme. Index Terms— Multi-class, Multiple Routing Tables, QoS, Routing. In this paper, we propose a distributed link state QoS routing with multiple routing tables obtained upon different link costs to effectively accommodate multi-class traffic such as real time QoS traffic and best–effort traffic. Each router in the network will maintain and compute two routing tables. The first one is for the shortest paths (minimum hops), the second for the QoS-based routing information. When a packet arrives at the router, the edge router will mark the packet whether it is a QoS or best- effort traffic and based on this mark the router will determine which table will be used for this packets. The significance of the proposed scheme lies in reducing the packet loss probability of the QoS traffic. This scheme can prevent the QoS traffic from concentrating on some links and allow at the same time to improve the best-effort traffic throughput. I. INTRODUCTION W ith the increasing diversity of network applications, it has become crucial for networks such as the Internet to offer various services, including best-effort services and guaranteed services. In the Internet a simple shortest path routing algorithm is employs. This routing may suffice in networks that provide only a single best-effort service in which there is no guarantee about whether and when a packet will be delivered. However it may not be adequate in networks that provide Quality of Service (QoS) guarantees to applications such as real time applications. These applications demand a guaranteed amount of network resources such as bandwidth etc. Hence, given a set of QoS requirements for a flow, the routers should be able to find a path satisfying these requirements. The rest of the paper is organized as follows. Section II provides some related works. The proposed algorithm overview will be given in section III. Experiments results are shown in Section IV. Finally, Section V draws the conclusion. Since the current routing protocols used in IP networks do not support the quality-of-service that different flows require. This can deteriorate the performance of the QoS II. RELATED WORK This work was supported in part by the Ministry of Education, Culture, Sports, Science and Technology, Japan, Grant-in-Aid for Scientific Research (A), 15200005, 2003, and in part by the Ministry of Public Management, Home Affairs, Posts and Telecommunications, Japan for Research and development for fostering younger excellent IT researchers of Strategic Information and Communications R&D Promotion Scheme QoS routing has attracted much attention recently. An extensive survey can be found in [4]. Open Shortest Path First (OSPF) [2] is a widely deployed link state routing protocol that has been an Internet standard for some time. The OSPF standard specifies that the routers run the shortest path dijkstra computation on their link state database, and determine a Hedia Kochkar, Takeshi Ikenaga and Yuji Oie are with Department of Computer Science and Electronics, Kyushu Institute of Technology, Iizuka 820-8502 Japan (email: {kochkar, ike, oie} @cse.kyutech.ac.jp). Yoshiaki Hori is with Department of Art and Information Design, Kyushu Institute of Design, Fukuoka 815-8540 Japan (email: hori@kyushu-id.ac.jp) 0-7803-7978-0/03/$17.00 ©2003 IEEE.