Service Level Agreements and Their Management in Packet Networks

The paper proposes a template for QoS-centered Service Level Agreements (SLA) and a framework for its real time management in multiservice packet networks. The SLA considered here are for QoS assured delivery of aggregate bandwidth fromingress to egress nodes, where the elementary entities are flows or calls of various QoS classes. A SLA monitoring scheme is presented in which revenue is generated by the admission of flows into the network, and penalty incurred when flows are lost in periods when the service provider is not SLA compliant. In the SLA management scheme proposed here the results of a prior design are used, in conjunction with measurements taken locally at ingress nodes, to classify the loading status of routes as either undersubscribed or oversubscribed. Our resource management is based on Virtual Partitioning and its supporting mechanism of Bandwidth Protection, which aims to carry as much of the offered flows at any time as is compatible with the protection of future undersubscribed routes. The effectiveness of our scheme is measured by the robustness in performance in the presence of great diversity in actual traffic conditions. We have built a comprehensive simulation testbud in software called D'ARTAGNAN from which we report numerical results for a case study. The results show that the SLC management scheme is robust, fair and efficient over a broad range of traffic conditions.