Research On Key Technologies Of Routing Paths Planning And Protection In Communication Networks

Communication network has become an important infrastructure in daily life. In the past years, with the rapid growth of cloud computing and mobile applications, more and more traffic runs on communication networks. These applications bring great challenges to the capacity, stability and robustness of communication networks. The routing planning and protection of traffic, which is one of the key problems in communication networks, has significant influence on the capacity, stability and robustness of communication networks. The routing planning of traffic demands will significantly influence the resource utilization in the networks, while providing protection for traffic demands can efficiently enhance the stability and robustness of networks. In this paper, we discuss the problem of traffic routing and protection, and focus on two problems, i.e., traffic protection in IP networks and routing planning in elastic optical networks.IP Fast Reroute(IP FRR) is the IETF standard for providing fast reaction to failures in IP and MPLS/LDP networks, which can reduce failure recovery time to tens of milliseconds. In the past decades, several IP FRR mechanisms have been proposed, and among them Loop-Free Alternates(LFA) is the simplest, but it cannot achieve 100% single failure coverage. In contrast, Maximally Redundant Trees(MRT) can provide 100%single failure coverage and seems a promising scheme. However, MRT may lead to long backup detours and heavy network congestion. In this paper, we combine MRT with LFA to merge their advantages and improve the quality of protection. Observations of performance evaluation suggest that compared to LFA, the proposed mechanism can protect against all single link/node failures and improve failure coverage; and compared to MRT,the proposed mechanism can greatly enhance the quality of protection in terms of backup path length and network congestion.The spectrum-sliced elastic optical path(SLICE) network has been proposed as a promising solution for flexible bandwidth allocation in optical transport networks. Flexible bandwidth allocation in SLICE networks promotes spectrum utilization efficiency,and thus increases the network capacity. One of the fundanmental problems in SLICE networks is the routing and spectrum allocation(RSA) problem, which computes a routing path and allocates spectrum for an arriving traffic demand. In this paper, we focus on the RSA problems in both dynamic and static traffic scenarios, and propose RSA algorithms to solve these problems.To solve the dynamic RSA problem, we decompose the problem into two subproblems, i.e., the routing sub-problem and the spectrum allocation sub-problem. For the routing sub-problem, we propose an efficient multi-constrained routing algorithm,namely Sorted Feasible Paths Searching(SFPS), to find the shortest feasible paths for dynamic traffic demands. The completeness, optimality as well as complexity of SFPS are proved. For the spectrum allocation sub-problem, we propose two spectrum allocation strategies, namely Fixed Segmentation(FS) and Adaptive Segmentation(AS) spectrum allocation strategies, which can mitigate the spectrum fragmentation and enhance network capacity. Performance of the proposed dynamic RSA algorithms is evaluated through extensive simulations. Simulation results prove that the proposed dynamic RSA algorithms are time-efficient and perform better than existing dynamic RSA algorithms,in terms of bandwidth blocking probability, spectrum fragmentation and resource utilization.To solve the static RSA problem, we sequentially compute the routing and spectrum allocation for traffic demands in some order, thus turning the static RSA problem into the dynamic RSA problem. Motivated by this idea, we propose a static RSA algorithm, namely Simulated Annealing-modified Maximum Reuse Spectrum Allocation(SA-mMRSA). SA-mMRSA includes two sub-algorithms, i.e., Simulated Annealingbased Static Planning(SASP) and modified Maximum Reuse Spectrum Allocation(mMRSA).Performance of the proposed static RSA algorithm is evaluated through extensive simulations. Numerical results of the evaluation reveal that the proposed algorithm can achieve near-optimal solutions in small static RSA problems; and compared to existing static RSA algorithms, the proposed algorithm can significantly reduce traffic blocking and enhance spectrum utilization.