Differential delay aware routing for Ethernet over SONET/SDH

The virtual concatenation protocol in SONET/SDH has ushered in a novel routing paradigm that enables a circuit to be "split" and routed over multiple paths. However, this diverse routing causes differential delay among the paths which can impact service if not accounted for in the routing. In this paper, we introduce the differential delay aware routing problem and show that it is not only NP-complete but is also provably hard to approximate within a constant factor. However, by transforming it into a flow routing formulation, we can derive effective, practical solutions. We present various algorithms and use extensive simulations to show that they are a good match to an "ideal" integer linear programming formulation. We also highlight how the differential delay data allows individual link delays to be reverse-engineered. We propose three algorithms to derive link delays including one that leverages the flexibility in the virtual concatenation protocol bits. Given the rise of next-generation applications such as online games where latency information is key, this knowledge of link delays, heretofore only loosely approximated, enables the telecom infrastructure to be more effective in supporting these applications.