The Resource Reservation Protocol (RSVP) is to gather outgoing interface identification information (e.g., outgoing interface ID's or IP addresses) for each node in a primary path. This information is "recorded" in an opaque object (referred to herein as the "RECORD PRIMARY PATH" or "RPP" object). In accordance with the present invention, the information contained in the opaque object is stored in two databases for each node, with local interface information of a particular node being stored in its Local Links Database (LLDB), and information identifying the primary links that affect the backup bandwidth calculation for that node being stored in its External Links Database (ELDB). Each node has its own LLDB and ELDB (or has the LLDB and ELDB data stored in a larger database in such a way that it is can be separately accessible on a node-by-node basis) so that, for each node, the information can be obtained and used. The admission controller at each node in the primary path uses the data in the LLDB and ELDB to compute the exact (least) amount of bandwidth required to be reserved on every link of the primary path.