Delay-constrained survivable multicast routing problem in WDM networks

In WDM network, link failure may cause service disruption and may lead to lose significant information. Especially, for a multicast transmission when link on a light-tree that carries traffic to multiple destinations failed, the traffic to all the downstream destinations along the failed link will be affected. For a given multicast request with a maximum delay denoted as Δ, the delay-constrained survivable multicast mechanism provides the primary multicast tree and some sparse resources to protect it. When link failure occurred, the multicast transmission is recovered by using sparse resources while ensuring that the backup tree can satisfy the delay constraint. This problem is called Delay-Constrained Survivable Multicast Routing Problem (DCSMRP). In this article, three protection methods are used to solve this problem; they are: Delay Constrained Link-disjoint Tree Protection (DCLTP), Delay Constrained Disjoint-Paths Protection (DCDPP) and Delay Constrained Span p-Cycle Protection (DCSP). Three multicast routing methods are proposed for the respective protecting methods to find the primary multicast tree and backup resources with delay constraint. Experiments are conducted to evaluate the resource utility ratio (RUR), blocking ratio (BR) and executing time (RT) of these methods. Simulations show that the DCSP method can get best BR for the cases with greater delay bound (for the cases with delay bound Δ > 5.5 ms.) The RUR of DCSP is worse than that of DCLTP and DCDPP (in the cases with delay bound Δ≥7.5msec), and the computational time of the DCDPP is faster than that of the DCSP and DCLTP.