A Bandwidth-Efficient and Low-Latency Packet Assembly Strategy for Optical Burst Switching in Metro Ring Prasanna Krishnamoorthy, Andrea Fumagalli Optical Networks Advanced Research (OpNeAR) Lab., Erik Jonsson School of EECS, University of Texas at Dallas Burst Switching LightRing Architecture LightRing Advantages Packets from a flow – same source, destination and class – are aggregated to make bursts These bursts, are transmitted all-optically through the core of the network Benefit Lower overhead Allows slower optical switching speeds 4 No loss In lossy Burst switching networks, larger bursts cause higher packet loss probability LightRing is lossless, hence we can build bigger bursts Ring topology Since path and intermediate nodes are known, aggregation can be done across multiple destinations Ring topology Multi-wavelength All-optical Token-based access protocol Loss-free, bandwidth on-demand Spatial Reuse 3 5 2 6 l1 l2 l3 1 7 8 Node Architecture Optical Burst Add Drop Multiplexer (OB-ADM) Aggregation Protocol QoS Protocol Different aggregation possibilities Same source, destination and class (S/D/C) Same source, destination, different classes (S/D) Same source, different destinations and classes (S) Aggregating different packet flows provides even better bandwidth efficiency more packets travel on the same burst number of burst requests go down latency goes down due to many flows being multiplexed Larger bursts can be created quicker due to lossless nature of LightRing ! Source OB-ADM node receives packets from external connection. aggregates packets into a burst transmits bursts all-optically to destination Destination OB-ADM de-multiplexes the packets from the burst transmits out of the network Token has a counter Counter keeps track of outstanding real-time traffic at all the nodes If counter increases, then best-effort traffic is not allowed onto the ring Only if counter decreases, best-effort traffic is allowed onto the ring Response Time Vs Throughput Variation with Ring Size a/D with Varying Load Summary Lossless transmission allows greater efficiency – since each burst can be larger Ring topology – intermediate nodes are known – allows same burst to have packets for different destinations Larger bursts more efficient (less overhead) Since more flows are used, bursts can be built quicker – lower latency 16 Nodes, 4 x OC-192, 80km 16 Nodes, 4 x OC-192 16 Nodes, 4 x OC-192, 80km