  VPN service providers (VSP) and IP-VPN customers have traditionally
maintained service demarcation boundaries between their routing and signaling
entities. This has resulted in the VPNs viewing the VSP network as an opaque
entity and therefore limiting any meaningful interaction between the VSP and
the VPNs. A key challenge is to expose each VPN to information about available
network resources through an abstraction (TA) [1] which is both accurate and
fair. In [2] we proposed three decentralized schemes assuming that all the
border nodes performing the abstraction have access to the entire core network
topology. This assumption likely leads to over- or under-subscription. In this
paper we develop centralized schemes to partition the core network capacities,
and assign each partition to a specific VPN for applying the decentralized
abstraction schemes presented in [2]. First, we present two schemes based on
the maximum concurrent flow and the maximum multicommodity flow (MMCF)
formulations. We then propose approaches to address the fairness concerns that
arise when MMCF formulation is used. We present results based on extensive
simulations on several topologies, and provide a comparative evaluation of the
different schemes in terms of abstraction efficiency, fairness to VPNs and call
performance characteristics achieved.
