RFC 3346 (rfc3346) - Page 3 of 14
Applicability Statement for Traffic Engineering with MPLS
Alternative Format: Original Text Document
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