MMSRP: multi-wavelength Markov-based split reservation protocol for DWDM optical networks

During wavelength reservation in Wavelength Division Multiplexed (WDM) optical networks, often multiple connection requests unknowingly compete for the same wavelength, even when other free wavelengths are available, resulting in a collision. The Markov model used in Markov Based Reservation Protocol (MBRP), is very effective to reduce such conflicts by intelligently guessing a wavelength in advance. Even then a connection request may be blocked because of the vulnerable period between wavelength probing and actual reservation. To minimize the effect of such vulnerability, splitting the probe process to fork out a partial reservation from an intermediate node is an efficient solution. In Markov-selection Split Reservation Protocol (MSRP), the above two strategies are combined, but only one wavelength is guessed during probing. If the attempt with this single wavelength fails, the connection request is blocked. To take care of this limitation, we propose here a new scheme called Multi-wavelength MSRP (MMSRP), where a set of wavelengths (instead of one) is selected by Markov model and continuously updated for possible future use. In case of failure, during reservation in the backward direction, it retries to reserve the next best wavelength through another splitting at the failure point. Thus, MMSRP handles multiple wavelengths sequentially through multiple splitting. Simulation results show that the blocking probability in MMSRP decreases considerably (~25% over MSRP and ~50% over MBRP in some cases) as the number of wavelengths increases. Compared to MSRP, though the average setup time is marginally higher in MMSRP, it appears quite promising for delay-tolerant applications, where blocking is very crucial, in dense WDM networks.