Technical Summary
There are various circumstances where it is highly desirable for a
Path Computation Client (PCC) to be able to dynamically and
automatically discover a set of Path Computation Elements (PCE),
along with some information that can be used for PCE selection. When
the PCE is a Label Switching Router (LSR) participating in the
Interior Gateway Protocol (IGP), or even a server participating
passively in the IGP, a simple and efficient way to discover PCEs
consists of using IGP flooding. For that purpose, this document
defines extensions to the Open Shortest Path First (OSPF) routing
protocol for the advertisement of PCE Discovery information within an
OSPF area or within the entire OSPF routing domain.
Working Group Summary
No dissent reported. The choice is relatively obvious for networks
running OSPF. Of course an IS-IS version is also needed for those
networks that are running IS-IS (and will be submitted to the IESG
soon).
Protocol Quality
Ross Callon has reviewed this spec for the IESG. I will check on
whether there are implementations.
Note to RFC Editor
Section 1: Insert two new terms in alphabetic order in the list
as follows:
PCED: PCE Discovery.
TLV: Type-Length-Variable data encoding.
Section 4.1
OLD
The PCE-ADDRESS sub-TLV is mandatory; it MUST be present within the
PCED TLV. It MAY appear twice, when the PCE has both an IPv4 and
IPv6 address. It MUST NOT appear more than once for the same
address type. If it appears more than once, only the first
occurrence is processed and any others MUST be ignored.
NEW
The PCE-ADDRESS sub-TLV is mandatory; it MUST be present within the
PCED TLV. It MAY appear twice, when the PCE has both an IPv4 and
IPv6 address. It MUST NOT appear more than once for the same
address type. If it appears more than once for the same address
type, only the first occurrence is processed and any others MUST be
ignored.
Section 5, in the fourth paragraph, remove the last two sentences.
Thus:
OLD
The PCE address (i.e., the address indicated within the PCE ADDRESS
sub-TLV) SHOULD be reachable via some prefixes advertised by OSPF.
This allows the detection of a PCE failure to be sped up. When the
PCE address is no longer reachable, the PCE node has failed, has
been torn down, or there is no longer IP connectivity to the PCE
node.
NEW
The PCE address (i.e., the address indicated within the PCE ADDRESS
sub-TLV) SHOULD be reachable via some prefixes advertised by OSPF.
Insert immediately after this paragraph:
The PCED TLV information regarding a specific PCE is
only considered current and useable when the router
advertising this information is itself reachable via
OSPF calculated paths in the same area of the LSA in which
the PCED TLV appears.
A change in the state of a PCE (activate, deactivate,
parameter change) MUST result in a corresponding change in
the PCED TLV information advertised by an OSPF router
(inserted, removed, updated) in its LSA. The way PCEs
determine the information they advertise and how that
information is made available to OSPF is out of the scope
of this document. Some information may be configured (e.g.,
address, preferences, scope) and other information may be
automatically determined by the PCE (e.g. areas of visibility).
Delete the last paragraph of section 5 (this paragraph begins "The
way PCEs determine...", and has been moved up in the text).
Replace all of section 9.3 with the following text:
9.3. Liveness Detection and Monitoring
This document specifies the use of OSPF as a PCE Discovery
Protocol. The requirements specified in RFC 4674 include the
ability to determine liveness of the PCE Discovery protocol.
Normal operation of the OSPF protocol meets these requirements.
Section 10
OLD
We would also like to thank Dave Ward, Lars Eggert, Sam Hartman, and
Tim Polk for their comments during the final stages of publication.
NEW
We would also like to thank Dave Ward, Lars Eggert, Sam Hartman, Tim
Polk, and Lisa Dusseault for their comments during the final stages
of publication.