Adaptive Wavelength Allocation in GMPLS Controlled Optical Network Rabindra Ghimire Department of Applied Science University of Arkansas at Little Rock Little Rock, Arkansas 72204 rxghimire@ualr.edu Seshadri Mohan Department of Systems Engineering University of Arkansas at Little Rock Little Rock, Arkansas 72204 sxmohan@ualr.edu Abstract— Different wavelength assignment schemes have been proposed in the literature for improving the blocking performance in optical networks. In this paper we analyze first fit and random wavelength assignment techniques. In the first fit case, the destination node selects the least indexed wavelength from the set of available wavelengths, whereas in random assignment the wavelength is selected randomly from the set of available wavelengths. In this paper, we propose a new wavelength assignment scheme that is highly adaptive. We begin by comparing the blocking performance of two schemes and observing that the first fit scheme outperforms the random assignment scheme if link utilization is high. In any network, link utilization varies from time to time; it is therefore desirable to switch between the wavelength assignment techniques depending on the link utilization so as to attain optimal blocking performance. Here, we propose an adaptive wavelength assignment (AA) technique that can dynamically switch between different wavelength assignment schemes based on link utilization. Our performance study indicates that, as the link utilization changes, the nodes adaptively select the best wavelength assignment technique in real time so as to improve the blocking performance. Keywords- adaptive routing; GMPLS; optical network; wavelength routing. I. INTRODUCTION Optical networks with wavelength division multiplexing (WDM) are emerging as candidates to handle the ever increasing demand for bandwidth. With the exponential growth in real-time applications over the internet, it is essential to employ a control plane protocol such as the Generalized Multi- protocol Label Switching (GMPLS) [1]. It is predicted that most of the future WDM networks will be wavelength routed network using GMPLS. In such networks two nodes communicate with each other via end-to-end optical connection known as lightpaths. In the absence of wavelength converters, a constraint is imposed requiring that an end-to-end connection be established using the same wavelength over all the links, a constraint that is referred to as wavelength continuity constraint (WCC). Real-time applications over the internet generate traffic that is dynamically varying and that requires frequent setup and release of connections. Traditional optical networks use static routing techniques in which lightpaths, once established, remain for a long period of time and, consequently, do not meet the dynamic traffic needs of real time applications. GMPLS framework has been standardized [2] which serves as an efficient and distributed dynamic lightpath establishment protocol. GMPLS employs open shortest path first with traffic engineering (OSPF-TE) as the routing protocol and resource reservation protocol with traffic engineering (RSVP-TE) as the signaling protocol. Whereas OSPF-TE floods the nodes with network topology information using which each node computes paths to other nodes in the network, RSVP-TE utilizes these paths to send signaling messages and establish lightpaths. Though GMPLS treats different levels of granularity, we utilize here only the wavelength level granularity. Because of WCC, one of the main challenges in a WDM network is to minimize the connection blocking probability and to avoid collision due to requests for the same wavelength due to concurrent connection setup [3]. The adaptive routing approach proposed in [4, 5] increases the probability of connection establishment by sharing network state information. Reference [6] discusses a collision aware wavelength assignment scheme. The wavelength assignment scheme employed heavily affects the blocking performance. Reference [7, 8] propose the most commonly adopted wavelength assignment schemes that include random assignment (RA), first fit (FF), and last fit (LF) schemes. In this paper, we analyze the blocking probability of distributed lightpath establishment using destination initiated reservation (DIR) [9] with RA and FF as wavelength assignment techniques and propose a new adaptive technique that improves the blocking performance. In RA, the destination node chooses the wavelength randomly from the set of available wavelengths that is carried by a path message of RSVP. In contrast, FF selects the least indexed wavelength from the set of available wavelengths carried by the path message. The last fit (LF) on the other hand selects the wavelength with higher index from the set of available wavelengths. The simulation results indicate that the RA scheme outperforms the FF scheme if the link utilization is low. The reverse is the case if the link utilization is high. Thus there exists some threshold point of utilization where the blocking performances of both schemes are identical. The link The research work was supported in part by the NSF Grant: EPS-0701890. Authorized licensed use limited to: University of Arkansas Litte Rock. Downloaded on June 30,2010 at 14:37:54 UTC from IEEE Xplore. Restrictions apply.