The Dynamics of Tcp and Udp Interaction in Ip- Qos Differentiated Services Networks

The results of a study using different drop precedence assignments to address fairness issues when UDP and TCP traffic share the same Assured Forwarding (AF) PHB class in Differentiated Services are presented. Six different combinations of drop-precedence assignments were explored using two different models of RED parameter settings. Results indicate that the type of RED model utilized can play a role in the nature of bandwidth sharing between TCP and UDP flows. The results also show that with the current four Class, three Drop Precedence AF specification, complete fairness between TCP and UDP cannot completely be achieved using separate drop-precedence assignments. This is true for both under-provisioned networks and over-provisioned networks. Certain drop-precedence mapping schemes benefit TCP, while others give advantage to UDP.