Providing resilient quality of service connections in provider-based virtual private networks

This thesis focuses on efficient provisioning of resilient Virtual Private Network (VPN) services. It first confirms the intuition that network resources can be more efficiently utilized when resilience mechanisms are implemented by a network provider in the physical network than by its VPN customers in their VPNs. Next, a Multiprotocol Label Switching-based programmable VPN architecture is presented that delivers virtual links as resilient quality of service (QoS) connections and virtual sites. Virtual sites allow customers to implement functionality like customized routing and content adaptation “in the cloud”, as opposed to the current network model where all functionality is implemented at the network edge. To provision a resilient QoS connection, two paths need to be computed from the ingress to the egress nodes, such that both paths meet the given QoS constraints. Two different frameworks have been proposed in the literature to compute resilient QoS connections when the QoS constraints are bandwidth and end-to-end delay. They both use a preprocessing step whereby either all links with less residual capacity than the given bandwidth constraint are pruned, or the given end-to-end delay is converted to an effective bandwidth. The frameworks thus reduce the problem to one with only a single constraint. We argue in this thesis that these frameworks individually lead to poor network utilization and propose a new framework where both constraints are considered simultaneously. Our framework exploits the dependency between endto-end delay, provisioned bandwidth and chosen path through using the provisioned bandwidth as a variable. Here, two link-disjoint paths are computed together with their respective minimum bandwidths such that both the bandwidth and end-to-end delay constraints are satisfied.