Routing in SONET/VCAT based optical WDM networks (Invited Paper)

In this paper, we investigate problems related to optical wavelength division multiplexing (WDM) networks that use the virtual concatenation (VCAT) mechanism of synchronous optical network (SONET) technology. VCAT, an end-to-end mechanism, allows SONET based optical WDM networks to carry traffic in finer granularity via multiple paths or a single path with multiple wavelengths. The benefits include efficient utilization of link capacity and implicit partial link failure protection if link-disjoint paths are used. However, multi-path routing causes differential delay among constituent paths and requires high-speed buffer capacity at receiving nodes. In this paper, we propose four route selection methods to study the tradeoffs of VCAT's traffic splitting feature. The performance analysis is conducted using a discrete-event simulation model. Optical WDM grooming networks under dynamic traffic demand are considered. The simulation results quantify the costs and benefits of using the VCAT mechanism in SONET based optical WDM networks. The simulation results confirm the benefits of carrying traffic in finer granularity. MP and SPMW consistently outperform the traditional SPSW method by 50 percent and 90 percent respectively in blocking performance. In the event of a link failure, the implicit protection ratio increases as connections use more link-disjoint paths. The results also show that differential delay, which is the cost of VCAT's multi-path routing, increases as the number of link-disjoint paths increases.