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 (PCEs),
along with information that can be used by the PCC 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 announce PCEs
consists of using IGP flooding. For that purpose this document
defines extensions to the Intermediate System to Intermediate System
(IS-IS) routing protocol for the advertisement of PCE Discovery
information within an IS-IS area or within the entire IS-IS routing
domain.
Working Group Summary
No dissent reported (see PROTO writeup by Adrian Farrel).
Protocol Quality
Ross Callon has reviewed the spec for the IESG. Two downref's were
called out during the second IETF last call, and have been added to
the downref directory. Also, note that this document is very similar
to the equivalent OSPF document, draft-ietf-pce-disco-proto-ospf.
The changes that came up during IESG review of the OSPF document
have also been made to this document.
Note to RFC Editor
The reference to [IS-IS-CAP] will need to be replaced by a reference
to RFC 4971.
Near the bottom of page 4, eigth paragraph of section 2 the double
paretheses should be removed. Thus "([IS-IS-CAP])" is replaced with
"[IS-IS-CAP]", or more precisely with "[RFC 4971]".
Section 4.1
OLD
The PCE-ADDRESS sub-TLV is mandatory; it MUST be present within the
PCED sub-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 sub-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 fifth 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 IS-IS.
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 IS-IS.
Insert immediately after this paragraph:
The PCED sub-TLV information regarding a specific PCE is
only considered current and useable when the router
advertising this information is itself reachable via
IS-IS calculated paths at the level of the LSP in which
the PCED sub-TLV appears.
A change in the state of a PCE (activate, deactivate,
parameter change) MUST result in a corresponding change in
the PCED sub-TLV information advertised by an IS-IS router
(inserted, removed, updated) in its LSP. The way PCEs
determine the information they advertise and how that
information is made available to IS-IS 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 IS-IS 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 IS-IS protocol meets these requirements.
Section 10
OLD
We would like to thank Lucy Wong, Adrian Farrel, Les Ginsberg, Mike
Shand, Lou Berger, and David Ward, for their useful comments and
suggestions.
NEW
We would like to thank Lucy Wong, Adrian Farrel, Les Ginsberg, Mike
Shand, Lou Berger, David Ward, Ross Callon, and Lisa Dusseault for
their useful comments and suggestions.