39 s use 0025 fig2 is an illustration of an exemplary wdm network having a working path and a plurality of possible protection paths the exemplary network consists of nodes a 100 b 102 c 104 d 106 e 108 and f 110 a working pathway between a and c is denoted with a solid line linking a to c through b in the case of a link failure within the working pathway for example a link from b to c 105 a 39 s traffic to c can be rerouted through e and f to reach c as denoted by the pathway denoted by the dotted and dashed links 112 114 and 116 between a e f and c this is an example of pathway protection as the entire pathway from a to c is protected by an alternate pathway alternatively the link between b and c can be protected by rerouting the link 39 s traffic through d as noted by the dashed links 118 and 120 the alternate route through d is therefore a protection path for the b to c link this is an example of link protection given a description of a wdm network g n e where n is the set of nodes and e is the set of links there exists a set of demands u which request light paths to be established across the networks these demands are protected by link based restoration paths for example each link i j on the working path of demand.