On managing traffic over virtual private network links

A Virtual Private Network (VPN) provides corporate networking between geographically dispersed company sites. VPN sites consist of Local Area Networks (LANs) interconnected over a public network infrastructure, through virtual links. The goal of this work is to develop a control model able to manage traffic on these links. By maximizing bandwidth utilization on each link, an optimum balance for the allocation of bandwidth on the entire VPN can be found. The proposed model is called hierarchical bandwidth manager and is implemented in each LAN of the VPN. It is also able to cope with best-effort and guaranteed flows so that bandwidth left unused by guaranteed flows is dynamically distributed among best-effort ones. In each LAN, a tree representation is used to share the capacity of each virtual link between multiple flows in a hierarchical and distributed manner. Each node in the tree respects an inter-node bandwidth share protocol and/or is regulated through an intra-host regulation mechanism. This latter is implemented through a new technique which we call the fair shaper. An implementation of this technique in a Solaris 2.5 operating system and results of the implementation of the inter-node bandwidth share protocol in the ns network simulator are also described in this paper.