A method to assist in deciding whether or not an ATM PNNI network link is able to sustain a new connection is described. The method comprises, if the link is not within an LCN exhaustion state and the new connection requests more bandwidth than is advertised as being available upon the link for the new connection's service category, regarding the bandwidth available for the new connection as a sum. The sum comprises addition of: 1) the advertised available bandwidth and 2) the total bandwidth reserved on the link for connections having lower priority than the new connection enhanced by over-subscription for the service category.