Constraint-based LSP setup by message reversing of CR-LDP

We investigate the problem of constraint-based routing that is one key component of traffic engineering. In constraint-based routing, resource information in addition to topology information is maintained in a database on all participating nodes in the routing domain. Especially the resource information of the links is changed rapidly because the bandwidth availability, for example, is changed whenever new LSPs are established and terminated. Therefore, the information used to compute a constraint-based path may be out-of-date. This means an LSP setup request may be blocked because a link or a node along the selected LSP has insufficient resources. This paper discusses the impact of inaccurate link state information, an LSP setup method coping with the inaccuracies, a new mechanism that allows constraint-based LSP setup and restoration, and gains obtained by our new mechanism.