Optik 124 (2013) 722–728 Contents lists available at SciVerse ScienceDirect Optik j o ur nal homepage: www.elsevier.de/ijleo An efficient resources allocation strategy for survivable WDM network under static lightpath demand Dharmendra Singh Yadav, Santosh Rana, Shashi Prakash ∗ Photonics Laboratory, Department of Electronics & Instrumentation, Institute of Engineering & Technology, Devi Ahilya University, Khandwa Road, Indore 452001, India a r t i c l e i n f o Article history: Received 30 August 2011 Accepted 11 January 2012 Keywords: Fault management Protection/restoration Routing and wavelength assignment (RWA) a b s t r a c t We present an optimized heuristic strategy for enhancing the utilization of network resources in sur- vivable WDM networks under static lightpath demand (SLD). The primary as well as backup connection establishment is efficiently managed in the proposed strategy. For the establishment of primary connec- tions, the requests are arranged in ascending order of the path lengths. If, for a connection request more than one shortest path/route is available in the network, then the route with the minimum wavelength index is selected. This results in uniform distribution of load among the links and avoids congestion. To enhance the backup lightpath establishment and increase restorability, a single wavelength of each link over the entire network is reserved in advance for setting up the path disjoint backup lightpaths. The effectiveness of the proposed strategy has been evaluated by undertaking extensive simulation experi- ments and the performance compared with respect to existing strategies of shared path protection (SPP) and hybrid connection approach (HCA). The network topologies of MESH, NATIONAL, and ARPANET have been used for the simulation. The results demonstrate that among all the strategies, the proposed strat- egy establishes maximum number of connections, avoids congestion, and uses the minimum network capacity (wavelength links). © 2012 Elsevier GmbH. All rights reserved. 1. Introduction In wavelength routed network data flows at a very high rate (in Tb/s). Here different wavelengths are combined by a multi- plexer and simultaneously transmitted over a single fiber using wavelength division multiplexing. Hence, wavelength division multiplexing (WDM) enhances the capacity of the optical networks. Each wavelength can support data rate up to several hundreds of Gbps for a lightpath. A lightpath is an optical route between the two nodes in the network. There are two types of lightpaths: the pri- mary lightpath and the backup lightpath. The lightpath that carries traffic during normal mode of operation is known as primary (active or working) lightpath. Since most of data flows over primary light- path, it must be the shortest path among all the available routes. When primary lightpath fails, the traffic is rerouted over a new lightpath, known as backup (reserved) lightpath [1]. In wavelength routed network two types of connection requests, either offline or online arrive. In offline connection requests, variables such as the set of source to destination pairs, the number of s–d requests, the connection setup and teardown time are known in advance. This is also known as scheduled lightpath demand (SLD) [4]. In SLD, if the ∗ Corresponding author. Tel.: +91 731 2361116/7; mobile: +91 9977186156; fax: +91 731 2764385. E-mail address: sprakash davv@rediffmail.com (S. Prakash). setup and tear down time are ignored, it is known as permanent lightpath demand (PLD) or static lightpath demand of the connec- tion requests [2,3]. If connection requests are arrange as per the increasing or decreasing order of their path length this is known as sequential routing in WDM network [2,3,5]. In online mechanism connection requests arrive randomly. This mode is also known as dynamic or random traffic demand. For the establishment of con- nection, it is necessary to search a route and assign wavelength to that route; this is known as routing and wavelength assign- ment problem (RWA) in WDM networks. If, route consists of the same wavelength in all the traversing links, it is known as wave- length continuity constraint (WCC). Another possibility is the use of different wavelengths among different (traversing links of light- path) links of the route because of the unavailability of the same wavelength along all the paths of the network. This is known as non-wavelength continuity constraints (NWCC). NWCC efficiently utilizes network capacity, but node must have the wavelength con- version capability. If, every node in the network has wavelength conversion capability, then the network is known as full wave- length conversion network. Wavelength converters are expensive and increase the node processing time, therefore WCC is preferred over NWCC. Moreover, WCC is simple to implement in wavelength routed networks. If the lightpath is disrupted, huge volume of traffic loss occurs. Failure of connection may be due to fiber cut or node failure in the network. To make connections survivable redundant capacity 0030-4026/$ – see front matter © 2012 Elsevier GmbH. All rights reserved. doi:10.1016/j.ijleo.2012.01.017