Spare capacity allocation using shared backup path protection for dual link failures

This paper extends the spare capacity allocation (SCA) problem from single link failure [1] to dual link failures on mesh-like IP or WDM networks. The SCA problem pre-plans traffic flows with mutually disjoint one working and two backup paths using the shared backup path protection (SBPP) scheme. The aggregated spare provision matrix (SPM) is used to capture the spare capacity sharing for dual link failures. Comparing to a previous work by He and Somani [2], this method has better scalability and flexibility. The SCA problem is formulated in a non-linear integer programming model and partitioned into two sequential linear sub-models: one finds all primary backup paths first, and the other finds all secondary backup paths next. The results on five networks show that the network redundancy using dedicated 1+1+1 is in the range of 313-400%. It drops to 96-181% in 1:1:1 without loss of dual-link resiliency, but with the trade-off of using the complicated share capacity sharing among backup paths. The hybrid 1+1:1 provides intermediate redundancy ratio at 187-310% with a moderate complexity. We also compare the passive/active approaches which consider spare capacity sharing after/during the backup path routing process. The active sharing approaches always achieve lower redundancy values than the passive ones. These reduction percentages are about 12% for 1+1:1 and 25% for 1:1:1 respectively

Survivability Analysis on Non-Triconnected Optical Networks under Dual-Link Failures

Survivability of optical networks is considered among the most critical problems that telecommunications operators need to solve at a reasonable cost. Survivability can be enhanced by increasing the amount of network links and its spare capacity, nevertheless this deploys more resources on the network that will be used only under failure scenarios. In other words, these spare resources do not generate any direct profit to network operators as they are reserved to route only disrupted traffic. In particular, the case of dual link failures on fiber optic cables (i.e., fiber cuts) has recently received much attention as repairing these cables typically requires much time, which then increases the probability of a second failure on another link of the network. In this context, survivability schemes can be used to recover the network from a dual link failure scenario. In this work, we analyze the case of protection and restoration schemes, which are two well-known recovery strategies. The former is simpler to implement as it considers a fixed set of backup paths for all failure scenarios; however, it cannot take into account the spare capacity released by disrupted connections. Instead, the latter computes the best recovery path considering not only the spare capacity but also the released one due to failures. Achieving 100% survivability (i.e., recovery from all possible dual link failures) requires a triconnected network, where three disjoint paths for each connection are required. Since these networks can become extremely expensive since they can require a huge number of network links (i.e., fibers connections), a more realistic case of non-triconnected networks is assumed. In these networks, full network recovery is not be feasible, but achieving the maximum possible survivability is desired. Spare capacity can then be allocated to existing network links, which represents the actual cost of the survivability. We propose optimization models that take into account these different recovery strategies, and demonstrate that restoration has the potential to provide a much better recovery capability with almost the same amount of spare capacity required in protection schemes.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Survivability Analysis on Non-Triconnected Optical Networks under Dual-Link Failures

Survivability of optical networks is considered among the most critical problems that telecommunications operators need to solve at a reasonable cost. Survivability can be enhanced by increasing the amount of network links and its spare capacity, nevertheless this deploys more resources on the network that will be used only under failure scenarios. In other words, these spare resources do not generate any direct profit to network operators as they are reserved to route only disrupted traffic. In particular, the case of dual link failures on fiber optic cables (i.e., fiber cuts) has recently received much attention as repairing these cables typically requires much time, which then increases the probability of a second failure on another link of the network. In this context, survivability schemes can be used to recover the network from a dual link failure scenario. In this work, we analyze the case of protection and restoration schemes, which are two well-known recovery strategies. The former is simpler to implement as it considers a fixed set of backup paths for all failure scenarios; however, it cannot take into account the spare capacity released by disrupted connections. Instead, the latter computes the best recovery path considering not only the spare capacity but also the released one due to failures. Achieving 100% survivability (i.e., recovery from all possible dual link failures) requires a triconnected network, where three disjoint paths for each connection are required. Since these networks can become extremely expensive since they can require a huge number of network links (i.e., fibers connections), a more realistic case of non-triconnected networks is assumed. In these networks, full network recovery is not be feasible, but achieving the maximum possible survivability is desired. Spare capacity can then be allocated to existing network links, which represents the actual cost of the survivability. We propose optimization models that take into account these different recovery strategies, and demonstrate that restoration has the potential to provide a much better recovery capability with almost the same amount of spare capacity required in protection schemes.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Survivability Analysis on Non-Triconnected Optical Networks under Dual-Link Failures

Survivability of optical networks is considered among the most critical problems that telecommunications operators need to solve at a reasonable cost. Survivability can be enhanced by increasing the amount of network links and its spare capacity, nevertheless this deploys more resources on the network that will be used only under failure scenarios. In other words, these spare resources do not generate any direct profit to network operators as they are reserved to route only disrupted traffic. In particular, the case of dual link failures on fiber optic cables (i.e., fiber cuts) has recently received much attention as repairing these cables typically requires much time, which then increases the probability of a second failure on another link of the network. In this context, survivability schemes can be used to recover the network from a dual link failure scenario. In this work, we analyze the case of protection and restoration schemes, which are two well-known recovery strategies. The former is simpler to implement as it considers a fixed set of backup paths for all failure scenarios; however, it cannot take into account the spare capacity released by disrupted connections. Instead, the latter computes the best recovery path considering not only the spare capacity but also the released one due to failures. Achieving 100% survivability (i.e., recovery from all possible dual link failures) requires a triconnected network, where three disjoint paths for each connection are required. Since these networks can become extremely expensive since they can require a huge number of network links (i.e., fibers connections), a more realistic case of non-triconnected networks is assumed. In these networks, full network recovery is not be feasible, but achieving the maximum possible survivability is desired. Spare capacity can then be allocated to existing network links, which represents the actual cost of the survivability. We propose optimization models that take into account these different recovery strategies, and demonstrate that restoration has the potential to provide a much better recovery capability with almost the same amount of spare capacity required in protection schemes.Sociedad Argentina de Informática e Investigación Operativa (SADIO