Network survivability is an important problem for WDM(Wavelength division multiplexing) transport network design.In network architecture using overlay mode

internal dependence of lightpaths could lead to the critical status that the failure of a physical fiber leaves the virtual topology unconnected.This may make the restoration of service by the higher level networks using the WDM network (such as SDH(Synchronous digital hierarchy))

ATM((Asynchronous transfer mode) or IP) impossible.It is necessary to avoid the above cases while embedding virtual topology into physical topology.VTMPD(Virtual topology mapping for protection design) algorithm proposed in this paper aims at Design Protection

considering load balance and capacity constraint of physical links simultaneously.We also compare the performance of VTMPD with the existent DAP(Disjoint alternate path) algorithm.The numerical results show that VTMPD algorithm is better than DAP algorithm.