O'Reilly logo

MPLS Fundamentals by Luc De Ghein - CCIE No. 1897

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

PCALC

PCALC is the special SPF algorithm that MPLS TE uses. SPF is an algorithm that OSPF and IS-IS use to calculate the shortest path to a destination. In short, SPF runs on every router and uses the database built by OSPF or IS-IS to distill a routing table. The only criterion that is important to SPF is the lowest cost for each IP prefix. For TE, however, other criteria play a role: the resources or constraints on the links. Because OSPF and IS-IS have been extended to distribute these resources, too, PCALC can calculate a path not only based on shortest path but also based on these resources. The SPF algorithm becomes a CSPF algorithm. Basically, links that do not have sufficient bandwidth or that do not have the right resources are pruned ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required