Models And Methods Of Pce-based Inter-as Vpn Path

With the emergence of multimedia audio and video services, network users require the higher demand of QoS and reliability. As one of the main technologies for multimedia services, VPN has been widely used in the internet, because of its high safety. When a router computes inter-domain traffic engineering paths, a large amount of CPU resources will be consumed. And most of the existing researches are based on the single domain, small-scale network. This paper utilizes path computation elements (PCE) to compute reliability-constrained inter-domain paths and realize inter-domain VPN path computation. We improve the Backward Recursive PCE-based Computation (BRPC) algorithm to compute the reliability-constrained inter-domain path. Some extensions to the PCE communication Protocol (PCEP) are proposed to support PCE for inter-domain VPN path computation. This paper has done some researches in this area.Firstly, a detailed analysis of the PCE-based inter-domain path computation is provisioned in multi-domain, large-scale heterogeneous networks. We compare the performance of the following three routing mechanisms: the PCE scheme, hierarchical routing scheme and the per-domain path computation scheme respectively. The rusults of the theoretical analysis show that the PCE scheme has better performance in inter-domain TE LSPs computation.Secondly, because of the limited visibility of the inter-domain network topology, reliability-constrained path computation is more challenging in the inter-domain scenario. A novel algorithm is proposed in this paper based on Backward Recursive PCE-based Computation algorithm to achieve a reliable inter-domain path with least-cost and high efficiency. Two decision thresholds, i.e., boundary node threshold and protect path threshold are also proposed to optimize the path computation. The BNT is used to decide which path segment needs the protected path. The PPT is used to decide which boundary node is feasible to satisfy the reliability requirement. The simulations show that the improved BRPC algorithm increases the success ratio of the path computation and reduces the path cost.Thirdly, in order to utilize PCE to compute inter-domain VPN paths, some extensions to the PCE communication Protocol is considered firstly. We extend the END-POINTS object to include VPN-IP routing information, and define a new VPN object to distinguish multiple VPN PCReq messages. Then a PCE-based model is created based on the cooperation of PCEs. In the PCE-based model, a policy for path computation request partition is proposed to obtain the feasible inter-domain VPN paths via different domains. Finally, an inter-domian P2MP VPN path computation algotithm is proposed according to the policy for path computation request partition. Simulation results show the inter-domian P2MP VPN path computation algotithm has less path cost and slightly lower blocking probability than the traditional P2P path computation based on BRPC algorithm.