Convergence time in VPNs

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Convergence time for a network is the time it needs to adapt to a new situation. This new situation can appear in a number of way but in this thesis only two possible changes are looked upon, when a link in the network fails and when a link recovers again. Today, convergence time is an important issue for network service providers since they want to give their customers access to the best network available. This means that the network convergence should be as fast as possible. For the Virtual Private Network (VPN) service, it is crucial that the convergence time is low since the VPN service gives the customer the impression that he is working on a Local Area Network between the company's offices and not through a service provider backbone. The VPN services looked upon in this thesis use an Multi Protocol Label Switched (MPLS) core network which uses label switching to forward the packets. To make this possible, a few protocols are used. Border Gateway Protocol (BGP) is used on the access links between the core network and the customers and between different autonomous systems in the core network for distributing and receiving reachability information about the VPN. Label Distribution Protocol (LDP) or sometimes even ReSource reserVation Protocol - Traffic Extension (RSVP-TE) is used for distributing labels and enabling label switching in the core. In this thesis, these protocols are looked upon and the relevant parameters are extracted. These parameters are theoretically looked upon and optimizations are then proved by practical testing. From t...