Survey of QoS Routing

Various real-time services, like webcasting, audio/videoconferencing and telemedicine, are being deployed over the Internet. This requires the network to provide the guarantee of the service being provided to the receiver. The needs of the application is specified in terms of the Quality of Service (QoS) metrics like desired bandwidth, response time, etc. End-to-end QoS can be provided most efficiently when each layer of the protocol stack translates the application provided requirement into layer specific requirement and satisfies the same. Network layer has a critical role to play in the QoS provision process. It provides the desired QoS by considering the QoS metrics in the path selection process. The focus of this paper is on the QoS routing algorithms and protocols for unicast and multicast in the IPv4 based Internet that constrains or optimizes an individual or combination of metrics. The desired features of a router supporting QoS have been discussed in detail. QoS routing leads to an increase in computation (more complex path selection process) and communication (protocol overhead due to increase in state information). However, the increase in cost is counterbalanced by the increase in performance. A study of work related to the cost/performance tradeoff of QoS routing is presented. Being an area of active research, QoS routing has a number of open issues that has been discussed as part of this paper.