Internet QoS Routing with IP Telephony and TCP Traffic

In this paper, we propose the use of QoS routing to enhance the support of IP Telephony. Our proposed scheme is based on QoS intradomain OSPF routing, an extension of the conventional OSPF routing protocol. A Diff Serv model is used (no per flow signalling, nor per flow accounting at intermediate nodes). Processing O/H is shifted from core to edge routers, which compute routes, monitor QoS path quality and enforce Call Acceptance Control (CAC) using the link state information advertised by OSPF. Via simulation, we show significant delay and throughput improvement over IP telephony strategies currently used in the Internet. In particular, hot spots and focussed congestion points are easily avoided. Moreover, the ability to control voice via QoS routing and CAC permits us to adjust the capacity sharing between voice traffic and TCP traffic, by reserving a fraction of link bandwidth to TCP data traffic. We also show that the added control and processing overhead is quite manageable, even in fairly large networks. Keywords— Open Shortest Path First, Class Based Queues, Quality of Service, Call Acceptance Control, routing, IP telephony .