Efficient Neighbor Channel Reservation (ENCR) for Contention Resolution in OBS Networks

Abstract

Optical burst switching (OBS) is an intermediate solution between optical packet switching and optical circuit switching. In OBS, resources are reserved on the y and released when the burst is passed. Contention occurs when two bursts want to use the same wavelength on an intermediate node and ultimately one of the burst has to be dropped. There are several solutions proposed in wavelength, time, and space de ection domain but each has its own limitations. We propose an algorithm for contention resolution in the domain of space de ection, named as E cient Neighbor Channel Reservation (ENCR). Among resource reservation protocols for OBS we use JET (Just Enough Time), whose performance is generally considered superior to other protocols. If contention occurs we utilize a neighbor link instead of drop- ping the packet straight away. We send the contending burst to a neighbor node, from where it is returned back to the de ecting node before following its original path. Two ags are used in the control packet to di erentiate a de ected burst from an original burst and for returning it back to the de ecting node from where it arrives. Our proposed scheme does not use any extra hardware, and addresses several limitations of previous schemes including eliminating the use of bulky Fiber Delay Lines (FDLs), prevent- ing out of order arrivals that may happen when burst segmentation is used, preventing resource wastage that occurs in case of pre-reservation schemes and prevention of loop formation that exists in current de ection routing schemes. Extensive simulations in NCUTns simulator have been conducted to test various parameters and e ectiveness of the proposed algorithm and the results veri es our research hypothesis. Index Terms- OBS, ENCR, Contention Resolution, Routing Optimization, Path Selection.