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Constrained Shortest Path First
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<p>Constrained Shortest Path First (CSPF) is an extension of shortest path algorithms. The path computed using CSPF is a shortest path fulfilling a set of constraints. It simply means that it runs shortest path algorithm after <i>pruning</i> those links that violate a given set of constraints. A <i>constraint</i> could be minimum bandwidth required per link (also known as bandwidth guaranteed constraint), end-to-end delay, maximum number of links traversed, include/exclude nodes. CSPF is widely used in <a href="/facts/Multiprotocol_Label_Switching/k7cx1PWw">MPLS</a> <a href="/facts/Teletraffic_engineering/vTKnPRfs">Traffic Engineering</a>. The routing using CSPF is known as <i>Constraint Based Routing</i> (CBR). </p><p>The path computed using CSPF could be exactly same as that of computed from <a href="/facts/OSPF/PACpGUHb">OSPF</a> and <a href="/facts/IS-IS/zaNkSwhW">IS-IS</a>, or it could be completely different depending on the set of constraints to be met. </p>