Fast updated Markov based Split Reservation Protocol in WDM Optical Networks

In WDM optical networks, two important steps during lightpath establishment, other than routing, are: wavelength selection and wavelength reservation. If two or more lightpaths compete for the same wavelength, wavelength collision occurs. An appropriate selection of wavelength is therefore very important to avoid such conflicts. The basic reason of the collision is the non availability of the updated wavelength usage information. Markov-based wavelength selection [7] guesses a unique wavelength in advance where each node periodically broadcasts its adjoining link usage information at a regular interval T. Within the interval T, all nodes use the previous update which is already outdated by time t is an element of [0,T]. In this work, we propose a novel technique to get around this problem without introducing any new control packets because the normal control packets, passing through the relevant nodes during that period, can be leveraged to carry the link state information. This allows to increase the value of T (thereby reducing broadcast overhead), when control packets are frequent in the network. We call this proposed modification of our previous work on Markov based Split Reservation Protocol (MSRP) [8] as Fast updated MSRP (FMSRP) where we "piggy-back" normal control packets with link usage information, in addition to usual broadcasting of the same at every T intervals. This, in turn, increases the probability to get latest information of link usage. We have compared FMSRP with MBRP and MSRP to show that the blocking probability improves considerably in some region of offered load.