Application performance and service differentiation for best effort traffic in ATM networks

Abstract

Best effort services continue to be simple and cheap and one of the most widely used networking services. For this class of service the network provides no QoS guarantees and applications compete with each other to gain the network resources they need. In this environment, the Packet Dropping Policy (PDP) is the most important and influential mechanism. PDPs can improve the application performance and the network utilization, achieve fairness among the competing connections, isolate traffic, and even provide service predictability and traffic differentiation. Although there are many Selective Packet Dropping mechanisms for the ATM Unspecified Bit Rate (UBR) service category, there is no single and best policy yet. All of them have advantages and disadvantages and finding a good policy for all scenarios is not easy. In this article we present a flexible PDP called Preemptive Partial Packet Discard (pPPD) that provides better application performance and network utilization than current alternatives. In addition, we demonstrate the flexibility of pPPD proposing four pPPD variants including pPPD-DS, meant to enhance the best effort service and provide relative traffic differentiation. pPPD-DS is proposed as a mechanism to implement the Behaviour Classes recently approved by the ATM Forum in the Differentiated UBR traffic management specifications for the support of the IETF Differentiated Model over ATM networks.