RFC 3346 (rfc3346) - Page 3 of 14

Applicability Statement for Traffic Engineering with MPLS

RFC 3346    Applicability Statement for Traffic Engineering  August 2002


2. Technical Overview of ISP Traffic Engineering

   Traffic engineering (TE) is generally concerned with the performance
   optimization of operational networks [2].  In contemporary practice,
   TE means mapping IP traffic flows onto the existing physical network
   topology in the most effective way to accomplish desired operational
   objectives.  Techniques currently used to accomplish this include,
   but are not limited to:

          1.  Manipulation of IGP cost (metrics)
          2.  Explicit routing using constrained virtual-circuit
              switching techniques such as ATM or Frame Relay SPVCs
          3.  Explicit routing using constrained path setup techniques
              such as MPLS

   This document is concerned primarily with MPLS techniques.
   Specifically, it deals with the ability to use paths other than the
   shortest paths selected by the IGP to achieve a more balanced network
   utilization, e.g., by moving traffic away from IGP-selected shortest
   paths onto alternate paths to avoid congestion in the network.  This
   can be achieved by using explicitly signaled LSP-tunnels.  The
   explicit routes to be used may be computed offline and subsequently
   downloaded and configured on the routers using an appropriate
   mechanism.  Alternatively, the desired characteristics of an LSP
   (such as endpoints, bandwidth, affinities) may be configured on a
   router, which will then use an appropriate algorithm to compute a
   path through the network satisfying the desired characteristics,
   subject to various types of constraints.  Generally, the
   characteristics associated with LSPs may include:

          o  Ingress and egress nodes
          o  Bandwidth required
          o  Priority
          o  Nodes to include or exclude in the path
          o  Affinities to include or exclude in the path
          o  Resilience requirements

   Affinities are arbitrary, provider-assigned, attributes applied to
   links and carried in the TE extensions for the IGPs.  Affinities
   impose a class structure on links, which allow different links to be
   logically grouped together.  They can be used to implement various
   types of policies, or route preferences that allow the inclusion or
   exclusion of groups of links from the path of LSPs.  Affinities are
   unique to MPLS and the original requirement for them was documented
   in [2].






Boyle, et al.                Informational