Optical Switching and Networking 9 (2012) 170–178 Contents lists available at SciVerse ScienceDirect Optical Switching and Networking journal homepage: www.elsevier.com/locate/osn A token-based routing mechanism for GMPLS-controlled WDM networks Rabindra Ghimire, Seshadri Mohan ∗ Department of Systems Engineering, University of Arkansas at Little Rock, Little Rock, AR, USA article info Article history: Available online 6 December 2011 Keywords: GMPLS Optical networks Token based routing Wavelength routing abstract This paper analyzes destination initiated reservation for Generalized Multi-Protocol Label Switching (GMPLS) based wavelength division multiplexing (WDM) networks and determines, via simulation, probabilities of both forward blocking and backward blocking. During light traffic load, any degradation in performance is due to backward blocking, whereas during heavy traffic load forward blocking dominates. In order to minimize performance degradation due to blocking, this paper proposes a token based routing scheme that is capable of searching for the availability of more than one route from source to destination, meeting the desired quality of service (QoS). Extensive simulation results show that the proposed technique significantly improves the blocking performance and setup delay. © 2011 Elsevier B.V. All rights reserved. 1. Introduction With increasing usage of real-time applications over the Internet, a majority of future networks will deploy wavelength division multiplexing (WDM) technology with Generalized Multi-Protocol Label Switching (GMPLS) as the control plane protocol. In such wavelength routed op- tical networks, the network nodes communicate with each other by establishing end-to-end optical connec- tion known as lightpaths. Traditional optical networks use static routing techniques in which lightpaths, once estab- lished, remain for a long period of time. In the next gen- eration networks, traffic will be more dynamic requiring frequent setup and release of lightpaths, and hence the tra- ditional technique is not an optimal choice. As a result of dynamic real time traffic, the number of signaling mes- sages initiated to establish and release a call will increase. In the absence of wavelength converters in an optical net- work, lightpaths must be established using the same wave- length (also called a lambda) on each link in its route, a ∗ Corresponding author. Tel.: +1 501 683 7475. E-mail addresses: rxghimire@ualr.edu (R. Ghimire), sxmohan@ualr.edu (S. Mohan). constraint known as wavelength continuity constraint. Key challenges in a WDM network are to minimize the connec- tion blocking probability, signaling overhead, and connec- tion setup delay. Internet Engineering Task Force (IETF) is working to en- sure the applicability of GMPLS for real time applications. Most of the literature on GMPLS concentrates on routing and signaling within the GMPLS network [1–4]. In order to support real time applications, dynamic connection estab- lishment and release must be carefully addressed [5]. Since requests for the establishment and release of lightpaths are dynamic, the availability of a specific wavelength in each link varies randomly. Therefore a significant challenge ex- ists in establishing end-to-end multi-hop lightpaths to provide QoS. One of the main challenges in a WDM net- work is to minimize the connection blocking probability. Several papers in the literature address this issue with different approaches. To tackle the dynamic connection establishment problem, the network control mechanism must be distributed, which is standardized within the GMPLS framework [6]. In a distributed network control mechanism, the link state information needs to be shared with all the network elements. Each node maintains a local database that stores the link state information so as to facilitate routing in 1573-4277/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.osn.2011.11.003