A comprehension study of Distributed QoS Approach based on Selective Probing

Abstract

The emergence of many new real-time network applications has great influence on the network routing algorithms. The routing function in the current internet is limited to provide "best-effort" service, which means it will try its best to forward user's data packets, but can provide no guarantees regarding bandwidth and delay. While this kind of service is suitable for some traditional applications such as ftp & telnet but it is not adequate for upcoming high-speed and real-time services such as audio-video real-time transmission, virtual private networks which requires strict delay & bandwidth guarantee. There are many facets for the guarantee of the Quality of Service. However the one of the key technology is QoS routing. The basic problem of QoS routing is to find a path satisfying multiple constraints. It is concerned with identifying the path that will consider multiple parameters like bandwidth, delay, cost, hop count etc. instead of one. QoS routing can be implanted in both of the routing strategies - Source routing & distributed routing for the traffic flow. In source routing, the path computation is done at source node whereas in distributed routing, the path computation is distributed among intermediate routers between source and destination. Both Sources routing and distributed routing have important roles to play in QoS routing. Source routing is seen impractical in Internet as the complete explicit path would have to be included in the IP header. Source routing is used in today's Internet for special cases only, such as mapping the network with trace route, troubleshooting etc. Distributed routing is currently the dominant method in Internet. Many distributed QoS algorithms have been proposed in literature by varying the QoS metrics and protocols. An important contribution in these works is [9]. This paper portrays the work of distributed routing approach mentioned in [9].