A Viable Translucent Architecture for Lossless OBS Networks

Optical transmission allows massive data transfers thanks to its tremendous transport capacity. Sustained efforts have been made to address the physical constraints that limit its flexibility, but as for today, translucent architectures involving electrical treatments are still favored. Optical Burst Switching (OBS) appears as a promising alternative to Optical Circuit Switching (OCS) in an all-optical framework - provided contention resolution is efficiently solved. In this paper, we investigate further contention resolution with a recourse to the electrical domain. We will thwart the drawbacks of the resulting translucent architecture, i.e., increased delays and equipment cost, by exploiting traffic grooming. Firstly, the contending payload will be submitted to a local aggregation process instead of being stored in dedicated buffers. Secondly, we propose a new transmission scheme, called CAROBS, that exploits dynamic traffic grooming, both at the network edge and in the core network. At the network edge, aggregation queues with different destinations can contribute to build burst trains whose cars can be later optically discarded, one or several at a time, at some intermediate nodes. In the core network, local traffic can be inserted at the tail/head of the train subject to some conditions. A proper dynamic management of the burst trains and of the aggregation pools allows a reduction of the aggregation delays and of the contention rate. Combining our grooming scheme with our translucent architecture annihilates the drawback of signal conversion: Loss-less transfer is achieved without neither impacting the delay nor the equipment cost. It results in an impressive throughput increase that puts OBS close to the performance of OCS with similar features and services, allowing to take full advantage of the high responsiveness to bursty traffic that OBS enjoys.