Constrained Shortest Path First (CSPF)


The Constrained Shortest Path First algorithm is used with Link State routing protocols such as OSPF and ISIS. It resolves Quality of Service routing queries, finding the best route (to an IPv4 or IPv6 destination address) that meets specified constraints, such as a specified minimum bandwidth.

DC-CSPF is a portable source code implementation of the CSPF algorithm for use with Metaswitch's IP Routing products. DC-CSPF maintains a local copy of the Link State database in a format optimized for this type of calculations, and uses it to generate a solution for each query.

DC-CSPF shares Metaswitch's unicast IP routing architecture. It is available for both IPv4 and IPv6 networks.

DC-CSPF Features

  • Contains database of traffic engineering link state information, including optical link state information, to calculate constraint-based shortest path first full source routes.
  • Calculations for IPv4 and IPv6 addresses
  • Configurable per-instance caching of routes minimizes route calculation time.
  • Multiple instances of CSPF can be distributed to line cards for scalability or redundancy.
  • Route calculations are all done locally with no communication with each IP Routing product's Protocol Manager. This provides increased performance and enables DC-CSPF to continue calculating routes even when the IP Routing product's Protocol Manager is not available, supporting high availability across failure of central processor.
  • Flexible interface for protection switching and fast restoration.
    • Calculation of node and link disjoint routes for protection switching.
    • Calculation of per-node and per-link protection paths.
  • Flexible customization options support many specialist usages.
  • Integrated with DC-OSPF, DC-ISIS and DC-MPLS through the customizable Route Selection Manager to provide a complete MPLS control plane.
  • High availability and fault tolerance in management of configuration information when used with Configuration Safe Store