MPLS TE Path Calculation

Introduction

MPLS TE use Constraint Shortest Path First (CSPF) algorithm to figure valid path for TE Tunnels.

TE Path Calculation

  • TE Path calculation provides the best shortest path for TE. CSFP algorithm ignores links that don't meet the constraints on the link attributes.
  • Path calculation does not find best route for all destination, but only the tunnel end points.
  • Links that meet constraints are used for path setup using RSVP TE.
  • Normally TE tunnels are not see as links in the links state database.

Decision Process

1. Pick the path with shortest cost that adhere to all constraints. Any link that does not obey constraints are pruned, proceed if multiple path exist.
2. Pick the path with largest minimal bandwidth, proceed if multiple paths still exist.
3. Pick the path with fewest hops, proceed if multiple paths still exist.
4. IOS picks one on top of the list as a tie breaker.

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