Given a set of connections, the problem of setting uplightpaths by routing and assigning a wavelength to each connectionis called the Routing and Wavelength-Assignment(RWA) problem. Typically, connection requests may be ofthree types: static, incremental, and dynamic [3]. With statictraffic, the entire set of connections is known in advance, andthe problem is then to set up lightpaths for these connectionsin a global fashion while minimizing network resources suchas the number of wavelengths or the number of fibers in thenetwork. Alternatively, one may attempt to set up as many ofthese connections as possible for a given fixed number ofwavelengths. The RWA problem for static traffic is known asthe Static Lightpath Establishment (SLE) problem. In theincremental-traffic case, connection requests arrive sequentially,a lightpath is established for each connection, and thelightpath remains in the network indefinitely. For the case ofdynamic traffic, a lightpath is set up for each connectionrequest as it arrives, and the lightpath is released after somefinite amount of time. The objective in the incremental anddynamic traffic cases is to set up lightpaths and assign wavelengthsin a manner that minimizes the amount of connectionblocking, or that maximizes the number of connections thatare established in the network at any time. This problem isreferred to as the Dynamic Lightpath Establishment (DLE)problem. In this study, we survey the different approaches tosolve both the static and the dynamic RWA problems
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