Flow Aware Differential Delay Routing for next-generation Ethernet over SONET/SDH

The introduction of Virtual Concatenation protocol in SONET/SDH has enabled an efficient transport of various data rates by allowing the traffic to be split and routed over multiple paths. However, diverse routing of circuits introduces a differential delay among the member paths capable of impacting service if not compensated at the sink node or accounted during routing. In this paper, we extend the previous work on differential delay aware routing problem and show that existing schemes do not accurately model the memory requirements of the network elements. We introduce the concept of Cumulative differential delay to address the shortcomings of the previous approaches. We also incorporate the concept of flow awareness in differential delay routing and combine it with the cumulative differential delay concept to define Cumulative differential delay routing (CDDR) problem. We study the theoretical complexity of the CDDR problem and show that it is not only NP-complete but is also provably hard to approximate within a constant factor. However, we develop a precomputation based algorithm and show that it is extremely efficient and effective in practice. We use simulations to show that it fares extremely well with the "ideal" integer linear programming formulation.