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Optical Packet Switching Using Multi-Wavelength Labels

par Pegah Seddighian
déposé le 21 février 2008

sous la direction de Leslie Ann Rusch
dans le département Génie électrique

We investigate optical networks capable of carrying data-type traffic. Our objective is to map Internet packets into optical packets and route them all-optically. We employ generalized multi-protocol label switching (GMPLS), where an optical label used for routing is assigned to each packet. We propose two different network structures based on multi-wavelength labels. We resolve the main drawbacks of previously proposed scenarios that are impractical and expensive due to high splitting loss and the complex technologies required. Our proposed network structures are practical, high-speed, simple, scalable, and low-cost. In the first approach, we use spectral amplitude codes (SAC) as labels, to accomplish ultra-fast packet forwarding. We propose stacking SAC-labels for hierarchical addressing, to reduce the size of lookup tables and splitting loss. We experimentally examine two optical packet formats, one with separable SAC-labels, and the other with SAC-encoded payloads. In the second approach, we propose a network structure based on binary multi-wavelength labels. Splitting losses are eliminated in this approach, rendering it even more scalable than our SAC proposal. In this scheme, the label is mapped bit-by-bit to a selection of wavelength bins. At the forwarding node, variable-length packets are self-forwarded over a multi-stage switch where each label bit controls a switch stage. The forwarding node is scalable and has fixed insertion loss. We also propose a solution to alleviate the sophisticated label swapping processing required in GMPLS networks. We time-multiplex the binary multi-wavelength labels for the entire optical label-switching path. We examine the performance of the proposed schemes experimentally as a proof of concept. Finally, we propose a solution for contention resolution, not addressed in the first two structures. We simplify the network topology to single-hop; the edge nodes are time-coordinated with the core nodes, thus optical synchronizers are not required. A non-centralized randomized scheduling algorithm is used to resolve contention; no optical buffer is required. A simple bipartite-graph matching algorithm is proposed to determine the connections at the core switch. We simulate the network for a realistic traffic type; the results confirm the good performance of the scheduling algorithm and establish that the proposed architecture is practical and desirable for packet-switched optical networks.