In the Next-Generation Network (NGN), accommodating a wide variety of customer networks through virtual private network (VPN) technologies is one of the key issues. In particular, a core network provider has to provide bandwidth-assured and secured data transmission for individual private networks while performing optimal and flexible path selection. We present hierarchically distributed path computation elements (HDPCEs) that enable a virtual private network (VPN) provider to guarantee end-to-end required bandwidth and to maintain the secrecy of the link-state information of each customer from other customers. In previous studies, a VPN provider only considered link states in the provider network and did not consider customer domains connected by the provider network. HDPCEs, which are distributed to customer domains, communicate with an HDPCE for the provider network, and these HDPCEs enable the guarantee of necessary bandwidth for a data transmission from one customer domain to another via a provider network. We propose a new path-selection algorithm in each HDPCE and cooperation scheme to interwork HDPCEs, which are suitable for VPN requirements. In the evaluation, the superiority of HDPCE-based VPN path selection over legacy OSPF-TE-based VPN path selection is demonstrated in two typical VPN models: the dedicated model and shared model.

Recently, integration of multiple network domains, such as optical fiber domains and packet domains, has been required by network providers and users. To achieve this interdomain integration, generalized multiprotocol label switching (GMPLS) is now receiving more attention. One of the main features of a GMPLS network is its multilayered complexity, which sometimes places a large burden on source GMPLS routers to determine optimal routes to destinations in other domains and causes label switching path (LSP)-setup delays. To reduce this source-router burden, we propose hierarchically distributed path computation equipment (HDPCE) that cooperates with each other to determine interdomain routes, reduce setup delay, and conduct flexible interdomain route creation taking individual GMPLS domain routing policies into consideration. Each domain routing policy can be set independently from that of other domains, and this routing information is not revealed to other peer domains because each HDPCE is allocated to every domain, including an interdomain, which has several underlying domains under it. Each underlying domain's HDPCE flexibly chooses three types of routing policies depending on the domain's requirement, and the interdomain HDPCE conducts interdomain route creation in accordance with underlying domain policies. OSPF routing protocol is now being applied to interdomain routing on GMPLS networks. Therefore, we compare the proposed HDPCE-based interdomain route creation with OSPF-based route creation in terms of performance and applicability, and we evaluate the effects of each underlying domain policy on interdomain route creation.