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.

Multilayered network interaction among various networks such as IP/MPLS packet networks and optical fiber networks are now achieved using generalized multiprotocol label switching (GMPLS) technology. One unique feature of GMPLS networks is that GMPLS packet-layer label switching paths (LSPs), such as IP/MPLS LSPs, sometimes tunnel through GMPLS lower layer LSPs such as optical fiber/lambda LSPs. One problem that occurs in this situation is protecting an important primary packet LSP by using a protection LSP that is physically separated from the primary LSP. The packet router has difficulty recognizing lower layer LSPs that are totally disjointed from the primary LSP. This is because, in a GMPLS's packet layer, a source router only differentiates one lower layer LSP from another, and does not check the disjointedness of segments through which the lower layer path passes. Sometimes, different lower LSPs pass through the same optical fiber, and a malfunction of one optical fiber sometimes causes many lower layer LSPs to malfunction at the same time. To solve this problem, a shared risk link group (SRLG) is introduced. Network links that belong to the same SRLG share a common physical resource. We apply this SRLG to the proposed hierarchically distributed path computation elements (HDPCEs) and achieve effective disjointed SRLG protection for important primary GMPLS packet paths.

The demand for intra- and interdomain routing for multilayered networks such as those using generalized multiprotocol label switching (GMPLS) is strong. One of the features that is peculiar to GMPLS networks is that because several different domains, such as those of IP, ATM, and optical fiber, are combined with each other hierarchically, various routing policies, which are sometimes independent from underlying domains and sometimes taking the underlying domains' policies into consideration, are required. For example GMPLS's lower layer LSPs like lambda LSP are expected to be established independently before the upper-layer LSPs, like IP and MPLS LSPs, are established in the underlying domains. Another requirement for the GMPLS interdomain routing is lightening the burden for selecting the interdomain route, because there are a lot of demands to interconnect many GMPLS domains. In order to satisfy these demands, we propose a path computation server (PCS) that is special for the intra/interdomain routing of GMPLS networks. As a counterpart of the proposed interdomain routing, it is now becoming popular to apply OSPF to the GMPLS interdomain routing. Therefore, we compared the proposed interdomain routing with OSPF, and show the applicability of the routing to GMPLS networks.