Traffic shaping and scheduling for OBS-based IP/WDM backbones

Mahmoud S. Elhaddad, Rami G. Melhem, Taieb Znati, Debashis Basak, Arun K. Somani, Zhensheng Zhang
2003 OptiComm 2003: Optical Networking and Communications  
We introduce Proactive Reservation-based Switching (PRS)-a switching architecture for IP/WDM networks based on Labeled Optical Burst Switching. PRS achieves packet delay and loss performance comparable to that of packet-switched networks, without requiring large buffering capacity, or burst scheduling across a large number of wavelengths at the core routers. PRS combines proactive channel reservation with periodic shaping of ingress-egress traffic aggregates to hide the offset latency and
more » ... t latency and approximate the utilization/buffering characteristics of discrete-time queues with periodic arrival streams. A channel scheduling algorithm imposes constraints on burst departure times to ensure efficient utilization of wavelength channels and to maintain the distance between consecutive bursts through the network. Results obtained from simulation using TCP traffic over carefully designed topologies indicate that PRS consistently achieves channel utilization above 90% with modest buffering requirements. A third approach, is Optical Burst Switching (OBS). [3] [4] [5] In an OBS network, IP packets are assembled into bursts at the ingress routers, and, ahead of each burst transmission, a burst header packet is forwarded on a dedicated control channel along the path of the burst. The header packets are processed electronically at every routers to compute the forwarding decision and to reserve router resources (e.g., output channel, FDL buffer, and wavelength converters) to the incoming burst. The resource allocations at a given router represent a schedule according to which arriving bursts are switched transparently through the router. The duration between the transmission of a header packet and its corresponding burst is called the transmission offset (simply, offset). The offset should be large enough so that the reservation request is processed at all routers ahead of burst arrival. In this paper, we introduce Proactive Reservation-based Switching (PRS), an IP/WDM switching architecture that overcomes the limitations of OBS, particularly, the limited bandwidth utilization efficiency of data and control channels, and the increased packet delay compared to packet switching. The proposed architecture combines a proactive reservation scheme with periodic shaping of ingress-egress traffic aggregates. This combination hides the offset latency and approximates the utilization/buffering characteristics of discrete-time queues with periodic arrival streams. A channel scheduling algorithm An OBS network consists of OBS nodes, also referred to as optical core routers or simply as core routers, and electronic edge routers connected by WDM links. Packets are assembled at network ingress into bursts. The bursts are then forwarded through the OBS network to the egress, where the bursts are disassembled back into packets. The edge routers must provide capability to assemble and disassemble bursts on interfaces facing the OBS network. On the other side the edge routers continue to support legacy interfaces such as SONET/SDH (POS) and Gigabit Ethernet. A core router consists of an optical switching matrix and a switch control unit. Prior to sending out a burst into the OBS network, core routers must be configured to switch the burst. This is achieved by sending out a reservation request (control) packet slightly ahead of time. The control packet traverses the OBS network
doi:10.1117/12.533541 fatcat:k774f7rn55dwjasxyabb2wlspq