RFC 3630 (rfc3630) - Page 2 of 14
Traffic Engineering (TE) Extensions to OSPF Version 2
Alternative Format: Original Text Document
RFC 3630 TE Extensions to OSPF Version 2 September 2003
particular, if non-TE capable nodes exist in the topology, they MUST
flood TE LSAs as any other type 10 (area-local scope) Opaque LSAs
(see [3]).
1.1. Applicability
Many of the extensions specified in this document are in response to
the requirements stated in [5], and thus are referred to as "traffic
engineering extensions", and are also commonly associated with MPLS
Traffic Engineering. A more accurate (albeit bland) designation is
"extended link attributes", as the proposal is to simply add more
attributes to links in OSPF advertisements.
The information made available by these extensions can be used to
build an extended link state database just as router LSAs are used to
build a "regular" link state database; the difference is that the
extended link state database (referred to below as the traffic
engineering database) has additional link attributes. Uses of the
traffic engineering database include:
o monitoring the extended link attributes;
o local constraint-based source routing; and
o global traffic engineering.
For example, an OSPF-speaking device can participate in an OSPF area,
build a traffic engineering database, and thereby report on the
reservation state of links in that area.
In "local constraint-based source routing", a router R can compute a
path from a source node A to a destination node B; typically, A is R
itself, and B is specified by a "router address" (see below). This
path may be subject to various constraints on the attributes of the
links and nodes that the path traverses, e.g., use green links that
have unreserved bandwidth of at least 10Mbps. This path could then
be used to carry some subset of the traffic from A to B, forming a
simple but effective means of traffic engineering. How the subset of
traffic is determined, and how the path is instantiated, is beyond
the scope of this document; suffice it to say that one means of
defining the subset of traffic is "those packets whose IP
destinations were learned from B", and one means of instantiating
paths is using MPLS tunnels. As an aside, note that constraint-based
routing can be NP-hard, or even unsolvable, depending on the nature
of the attributes and constraints, and thus many implementations will
use heuristics. Consequently, we don't attempt to sketch an
algorithm here.
Katz, et al. Standards Track