Revisiting Packet-Switched WDM Rings for Metro Networks: A Comprehensive Cross-Layer Assessment

Present-day metro networks employ SONET-based WDM rings, a circuit-switched architecture primarily designed to support the circuit-switched client (i.e., voice), and thus having inefficient bandwidth utilization in the presence of bursty packet-switched data traffic (e.g. ATM, Ethernet, IP). Despite several improvisations made in SONET to reduce its inefficiency for packet-switched client, SONET-over-WDM metro today finds it challenging to cope up with the ever-escalating bursty traffic from the access. As of now, the packet-switched WDM ring stands as a promising candidate for the next-generation metro networks, more so for the metro edges, the lower sub-segment of the metro networks, interfacing with the access network. Although, several testbeds have been developed for packet-switched WDM rings in the recent years, the viability of these designs highly depends on the latency of the proposed packet-based media-access protocols and the transmission impairments in the physical layer as the network scales in size. Addressing these problems, we revisit the previously proposed packet-switched WDM metro ring architectures and make a comprehensive study considering both the MAC as well as physical-layer issues, in order to deliver a design guideline for practically viable solutions to the network providers.