OSPF Protocol Extensions for Path Computation Element (PCE) Discovery
draft-ietf-pce-disco-proto-ospf-08
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 5088.
|
|
|---|---|---|---|
| Authors | Jean-Louis Le Roux , JP Vasseur , Raymond Zhang , Yuichi Ikejiri | ||
| Last updated | 2020-01-21 (Latest revision 2007-09-24) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 5088 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Ross Callon | ||
| Send notices to | (None) |
draft-ietf-pce-disco-proto-ospf-08
Network Working Group J.L. Le Roux (Editor)
Internet Draft France Telecom
Intended Status: Standard Track
Expires: April 2008 J.P. Vasseur (Editor)
Cisco System Inc.
Yuichi Ikejiri
NTT Communications
Raymond Zhang
BT Infonet
October 2007
OSPF Protocol Extensions for Path Computation Element (PCE) Discovery
draft-ietf-pce-disco-proto-ospf-08.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Copyright Notice
Copyright (C) The IETF Trust (2007). All rights reserved.
Le Roux, Vasseur et al. OSPF extensions for PCE discovery [Page 1]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
Abstract
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 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.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Table of Contents
1. Terminology.................................................3
2. Introduction................................................4
3. Overview....................................................5
3.1. PCE Discovery Information...................................5
3.2. Flooding Scope..............................................5
4. The OSPF PCED TLV...........................................6
4.1. PCE-ADDRESS Sub-TLV.........................................7
4.2. PATH-SCOPE Sub-TLV..........................................8
4.3. PCE-DOMAIN Sub-TLV.........................................10
4.4. NEIG-PCE-DOMAIN Sub-TLV....................................11
4.5. PCE-CAP-FLAGS Sub-TLV......................................11
5. Elements of Procedure......................................13
6. Backward Compatibility.....................................13
7. IANA Considerations........................................14
7.1. OSPF TLV...................................................14
7.2. PCE Capability Flags registry..............................14
8. Security Considerations....................................15
9. Manageability Considerations...............................15
9.1. Control of Policy and Functions............................15
9.2. Information and Data Model.................................15
9.3. Liveness Detection and Monitoring..........................15
9.4. Verify Correct Operations..................................16
9.5. Requirements on Other Protocols and Functional
Components...............................................16
9.6. Impact on Network Operations...............................16
10. Acknowledgments............................................16
11. References.................................................16
11.1. Normative References.......................................16
11.2. Informative References.....................................17
12. Editor's Addresses.........................................17
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 2]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
13. Contributors' Addresses....................................18
14. Intellectual Property Statement............................18
1. Terminology
ABR: OSPF Area Border Router.
AS: Autonomous System.
IGP: Interior Gateway Protocol. Either of the two routing
protocols Open Shortest Path First (OSPF) or Intermediate System
to Intermediate System (ISIS).
Intra-area TE LSP: A TE LSP whose path does not cross an IGP area
boundary.
Intra-AS TE LSP: A TE LSP whose path does not cross an AS
boundary.
Inter-area TE LSP: A TE LSP whose path transits two or more IGP
areas. That is a TE LSP that crosses at least one IGP area
boundary.
Inter-AS TE LSP: A TE LSP whose path transits two or more
ASes or sub-ASes (BGP confederations). That is a TE LSP that
crosses at least one AS boundary.
LSA: Link State Advertisement.
LSR: Label Switching Router.
PCC: Path Computation Client. Any client application requesting a
path computation to be performed by a Path Computation Element.
PCE: Path Computation Element. An entity (component, application,
or network node) that is capable of computing a network path or
route based on a network graph, and applying computational
constraints.
PCE-Domain: In a PCE context this refers to any collection of
network elements within a common sphere of address management or
path computational responsibility (referred to as a "domain" in
[RFC4655]). Examples of PCE-Domains include IGP areas and ASes.
This should be distinguished from an OSPF routing domain.
PCEP: Path Computation Element Protocol.
TE LSP: Traffic Engineered Label Switched Path.
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 3]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
2. Introduction
[RFC4655] describes the motivations and architecture for a Path
Computation Element (PCE)-based
path computation model for Multi-Protocol Label Switching (MPLS) and
Generalized MPLS (GMPLS) Traffic Engineered Label Switched Paths (TE
LSPs). The model allows for the separation of the PCE from a Path
Computation Client (PCC) (also referred to as a non co-located PCE)
and allows for cooperation between PCEs (where one PCE acts as a PCC
to make requests of the other PCE). This relies on a communication
protocol between PCC and PCE, and also between PCEs. The requirements
for such a communication protocol can be found in [RFC4657], and the
communication protocol is defined in [PCEP].
The PCE architecture requires that a PCC be aware of the location of
one or more PCEs in its domain, and also, potentially, of PCEs in
other domains, e.g., in the case of inter-domain TE LSP computation.
A network may contain a large number of PCEs, each with potentially
distinct capabilities. In such a context it is highly desirable to
have a mechanism for automatic and dynamic PCE discovery that allows
PCCs to automatically discover a set of PCEs along with additional
information about each PCE that may be used by a PCC to perform PCE
selection. Additionally, it is valuable for a PCC to dynamically
detect new PCEs, failed PCEs, or any modification to the PCE
information. Detailed requirements for such a PCE discovery mechanism
are provided in [RFC4674].
Note that the PCE selection algorithm applied by a PCC is out of the
scope of this document.
When PCCs are LSRs participating in the IGP (OSPF or IS-IS), and PCEs
are either LSRs or servers also participating in the IGP, an
effective mechanism for PCE discovery within an IGP routing domain
consists of utilizing IGP advertisements.
This document defines extensions to OSPFv2 [RFC2328] and OSPFv3
[RFC2740] to allow a PCE in an OSPF routing domain to advertise its
location along with some information useful to a PCC for PCE
selection so as to satisfy dynamic PCE discovery requirements set
forth in [RFC4674].
Generic capability advertisement mechanisms for OSPF are defined in
[OSPF-CAP]. These allow a router to advertise its capabilities within
an OSPF area or an entire OSPF routing domain. This document
leverages this generic capability advertisement mechanism to fully
satisfy the dynamic PCE discovery requirements.
This document defines a new TLV (named the PCE Discovery (PCED) TLV)
to be carried within the OSPF Router Information LSA ([OSPF-CAP]).
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 4]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
The PCE information advertised is detailed in Section 3. Protocol
extensions and procedures are defined in Sections 4 and 5.
The OSPF extensions defined in this document allow for PCE discovery
within an OSPF routing domain. Solutions for PCE discovery across AS
boundaries are beyond the scope of this document, and for further
study.
3. Overview
3.1. PCE Discovery Information
The PCE discovery information is composed of:
- The PCE location: an IPv4 and/or IPv6 address that is used to reach
the PCE. It is RECOMMENDED to use an address that is always
reachable if there is any connectivity to the PCE;
- The PCE path computation scope (i.e., intra-area, inter-area,
inter-AS, or inter-layer);
- The set of one or more PCE-Domain(s) into which the PCE has
visibility and for which the PCE can compute paths;
- The set of zero, one or more neighbor PCE-Domain(s) toward which
the PCE can compute paths;
- A set of communication capabilities (e.g., support for request
prioritization) and path computation-specific capabilities
(e.g., supported constraints).
PCE discovery information is by nature fairly static and does not
change with PCE activity. Changes in PCE discovery information may
occur as a result of PCE configuration updates, PCE
deployment/activation, PCE deactivation/suppression, or PCE failure.
Hence, this information is not expected to change frequently.
3.2. Flooding Scope
The flooding scope for PCE information advertised through OSPF can be
limited to one or more OSPF areas the PCE belongs to, or can be
extended across the entire OSPF routing domain.
Note that some PCEs may belong to multiple areas, in which case the
flooding scope may comprise these areas. This could be the case for
an ABR, for instance, advertising its PCE information within the
backbone area and/or a subset of its attached IGP area(s).
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 5]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
4. The OSPF PCED TLV
The OSPF PCE Discovery TLV (PCED TLV) contains non-ordered set of
sub-TLVs.
The format of the OSPF PCED TLV and its sub-TLVs is identical to the
TLV format used by the Traffic Engineering Extensions to OSPF
[RFC3630]. That is, the TLV is composed of 2 octets for the type, 2
octets specifying the TLV length, and a value field. The Length field
defines the length of the value portion in octets.
The TLV is padded to four-octet alignment; padding is not included in
the Length field (so a three octet value would have a length of
three, but the total size of the TLV would be eight octets). Nested
TLVs are also four-octet aligned. Unrecognized types are ignored.
The OSPF PCED TLV has the following format:
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// sub-TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type To be defined by IANA (suggested value=5)
Length Variable
Value This comprises one or more sub-TLVs
Five sub-TLVs are defined:
Sub-TLV type Length Name
1 variable PCE-ADDRESS sub-TLV
2 4 PATH-SCOPE sub-TLV
3 4 PCE-DOMAIN sub-TLV
4 4 NEIG-PCE-DOMAIN sub-TLV
5 variable PCE-CAP-FLAGS sub-TLV
The PCE-ADDRESS and PATH-SCOPE sub-TLVs MUST always be present within
the PCED TLV.
The PCE-DOMAIN and NEIG-PCE-DOMAIN sub-TLVs are optional. They MAY be
present in the PCED TLV to facilitate selection of inter-domain PCEs.
The PCE-CAP-FLAGS sub-TLV is optional and MAY be present in the PCED
TLV to facilitate the PCE selection process.
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 6]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
Malformed PCED TLVs or sub-TLVs not explicitly described in this
document MUST cause the LSA to be treated as malformed according to
the normal procedures of OSPF.
Any unrecognized sub-TLV MUST be silently ignored.
The PCED TLV is carried within an OSPF Router Information LSA
defined in [OSPF-CAP].
No additional sub-TLVs will be added to the PCED TLV in the future.
If a future application requires the advertisement of additional PCE
information in OSPF, this will not be carried in the Router
Information LSA.
The following sub-sections describe the sub-TLVs which may be carried
within the PCED sub-TLV.
4.1. PCE-ADDRESS Sub-TLV
The PCE-ADDRESS sub-TLV specifies an IP address that can be
used to reach the PCE. It is RECOMMENDED to make use of an address
that is always reachable, provided that the PCE is alive and
reachable.
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.
The format of the PCE-ADDRESS sub-TLV is as follows:
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| address-type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// PCE IP Address //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PCE-ADDRESS sub-TLV format
Type 1
Length 8 (IPv4) or 20 (IPv6)
Address-type:
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 7]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
1 IPv4
2 IPv6
Reserved: SHOULD be set to zero on transmission and MUST be
ignored on receipt.
PCE IP Address: The IP address to be used to reach the PCE.
4.2. PATH-SCOPE Sub-TLV
The PATH-SCOPE sub-TLV indicates the PCE path computation scope,
which refers to the PCE's ability to compute or take part in the
computation of paths for intra-area, inter-area, inter-AS, or inter-
layer_TE LSPs.
The PATH-SCOPE sub-TLV is mandatory; it MUST be present within the
PCED TLV. There MUST be exactly one instance of the PATH-SCOPE sub-
TLV within each PCED TLV. If it appears more than once, only the
first occurrence is processed and any others MUST be ignored.
The PATH-SCOPE sub-TLV contains a set of bit-flags indicating the
supported path scopes, and four fields indicating PCE preferences.
The PATH-SCOPE sub-TLV has the following format:
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|1|2|3|4|5| Reserved |PrefL|PrefR|PrefS|PrefY| Res |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 2
Length 4
Value This comprises a 2-octet flag field where each bit
represents a supported path scope, as well as four
preference fields used to specify PCE preferences.
The following bits are defined:
Bit Path Scope
0 L bit: Can compute intra-area paths
1 R bit: Can act as PCE for inter-area TE LSP
computation
2 Rd bit: Can act as a default PCE for inter-area TE LSP
computation
3 S bit: Can act as PCE for inter-AS TE LSP computation
4 Sd bit: Can act as a default PCE for inter-AS TE LSP
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 8]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
computation
5 Y bit: Can compute or take part into the computation
of paths across layers.
PrefL field: PCE's preference for intra-area TE LSPs
computation.
PrefR field: PCE's preference for inter-area TE LSPs
computation.
PrefS field: PCE's preference for inter-AS TE LSPs
computation.
PrefY field: PCE's preference for inter-layer TE LSPs
computation.
Res: Reserved for future use.
The L, R, S, and Y bits are set when the PCE can act as a PCE for
intra-area, inter-area, inter-AS, or inter-layer TE LSPs computation
respectively. These bits are non-exclusive.
When set, the Rd bit indicates that the PCE can act as a default PCE
for inter-area TE LSPs computation (that is, the PCE can compute a
path toward any neighbor area). Similarly, when set, the Sd bit
indicates that the PCE can act as a default PCE for inter-AS TE LSP
computation (the PCE can compute a path toward any neighbor AS).
When the Rd and Sd bit are set the PCED TLV MUST NOT contain a NEIG-
PCE-DOMAIN sub-TLV (see Section 4.1.4).
When the R bit is clear, the Rd bit SHOULD be clear on transmission
and MUST be ignore on receipt. When the S bit is clear, the Sd bit
SHOULD be clear on transmission and MUST be ignored on receipt.
The PrefL, PrefR, PrefS, and PrefY fields are each three bits long
and allow the PCE to specify a preference for each computation scope,
where 7 reflects the highest preference. Such preferences can be used
for weighted load balancing of path computation requests. An operator
may decide to configure a preference for each computation scope at
each PCE so as to balance the path computation load among them. The
algorithms used by a PCC to load balance its path computation
requests according to such PCE preferences is out of the scope of
this document and is a matter for local or network-wide policy. The
same or different preferences may be used for each scope. For
instance, an operator that wants a PCE capable of both inter-area and
inter-AS computation to be prefered for use for inter-AS computations
may configure PrefS higher than PrefR.
When the L, R, S, or Y bits are cleared, the PrefL, PrefR, PrefS, and
PrefY fields SHOULD respectively be set to 0 on transmission and MUST
be ignored on receipt.
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 9]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
Both reserved fields SHOULD be set to zero on transmission and MUST
be ignored on receipt.
4.3. PCE-DOMAIN Sub-TLV
The PCE-DOMAIN sub-TLV specifies a PCE-Domain (area or AS) where the
PCE has topology visibility and through which the PCE can compute
paths.
The PCE-DOMAIN sub-TLV SHOULD be present when PCE-Domains for which
the PCE can operate cannot be inferred by other IGP information, for
instance when the PCE is inter-domain capable (i.e., when the R bit
or S bit is set) and the flooding scope is the entire routing domain
(see Section 5 for a discussion of how the flooding scope is set and
interpreted).
A PCED TLV may include multiple PCE-DOMAIN sub-TLVs when the PCE has
visibility into multiple PCE-Domains.
The PCE-DOMAIN sub-TLV has the following format:
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=3 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain-type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PCE-DOMAIN sub-TLV format
Type 3
Length 8
Two domain-type values are defined:
1 OSPF Area ID
2 AS Number
Domain ID: With the domain-type set to 1, this indicates the 32
bit Area ID of an area where the PCE has visibility and can
compute paths. With domain-type set to 2, this indicates an AS
number of an AS where the PCE has visibility and can compute
paths. When the AS number is coded in two octets, the AS Number
field MUST have its first two octets set to 0.
.
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 10]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
4.4. NEIG-PCE-DOMAIN Sub-TLV
The NEIG-PCE-DOMAIN sub-TLV specifies a neighbor PCE-domain (area or
AS) toward which a PCE can compute paths. It means that the PCE can
take part in the computation of inter-domain TE LSPs with paths that
transit this neighbor PCE-domain.
A PCED sub-TLV may include several NEIG-PCE-DOMAIN sub-TLVs when the
PCE can compute paths towards several neighbour PCE-domains.
The NEIG-PCE-DOMAIN sub-TLV has the same format as the PCE-DOMAIN
sub-TLV:
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 4 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain-type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NEIG-PCE-DOMAIN sub-TLV format
Type 4
Length 8
Two domain-type values are defined:
1 OSPF Area ID
2 AS Number
Domain ID: With the domain-type set to 1, this indicates the 32
bit Area ID of a neighbour area toward which the PCE can
compute paths. With domain-type set to 2, this indicates the AS
number of a neighbor AS toward which the PCE can compute paths.
When the AS number is coded in two octets, the AS Number field
MUST have its first two octets set to 0.
The NEIG-PCE-DOMAIN sub-TLV MUST be present at least once with
domain-type set to 1 if the R bit is set and the Rd bit is cleared,
and MUST be present at least once with domain-type set to 2 if the S
bit is set and the Sd bit is cleared.
4.5. PCE-CAP-FLAGS Sub-TLV
The PCE-CAP-FLAGS sub-TLV is an optional sub-TLV used to indicate PCE
capabilities. It MAY be present within the PCED TLV. It MUST NOT be
present more than once. If it appears more than once, only the first
occurrence is processed and any others MUST be ignored.
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 11]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
The value field of the PCE-CAP-FLAGS sub-TLV is made up of an array
of units of 32 bit-flags numbered from the most significant bit as
bit zero, where each bit represents one PCE capability.
The format of the PCE-CAP-FLAGS sub-TLV is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 5 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// PCE Capability Flags //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 5
Length Multiple of 4 octets
Value This contains an array of units of 32 bit flags
numbered from the most significant as bit zero, where
each bit represents one PCE capability.
IANA is requested to manage the space of the PCE Capability Flags
The following bits are to be assigned by IANA:
Bit Capabilities
0 Path computation with GMPLS link constraints
1 Bidirectional path computation
2 Diverse path computation
3 Load-balanced path computation
4 Synchronized path computation
5 Support for multiple objective functions
6 Support for additive path constraints
(max hop count, etc.)
7 Support for request prioritization
8 Support for multiple requests per message
9-31 Reserved for future assignments by IANA.
These capabilities are defined in [RFC4657].
Reserved bits SHOULD be set to zero on transmission and MUST be
ignored on receipt.
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 12]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
5. Elements of Procedure
The PCED TLV is advertised within OSPFv2 Router Information LSAs
(Opaque type of 4 and Opaque ID of 0) or OSPFv3 Router Information
LSAs (function code of 12) which are defined in [OSPF-CAP]. As such,
elements of procedure are inherited from those defined in [OSPF-CAP].
In OSPFv2 the flooding scope is controlled by the opaque LSA type (as
defined in [RFC2370]) and in OSPFv3 by the S1/S2 bits (as defined in
[RFC2740]). If the flooding scope is local to an area then the PCED
TLV MUST be carried within an OSPFv2 type 10 router information LSA
or an OSPFV3 Router Information LSA with the S1 bit set and the S2
bit clear. If the flooding scope is the entire IGP domain then the
PCED TLV MUST be carried within an OSPFv2 type 11 Router Information
LSA or OSPFv3 Router Information LSA with the S1 bit clear and the S2
bit set. When only the L bit of the PATH-SCOPE sub-TLV is set, the
flooding scope MUST be area local.
When the PCE function is deactivated, the OSPF speaker advertising
this PCE MUST originate a new Router Information LSA that no longer
includes the corresponding PCED TLV, provided there are other TLVs in
the LSA. If there are no other TLVs in the LSA, it MUST either send
an empty Router Information LSA or purge it by prematurely aging it.
The PCE address (i.e., the address indicated within the PCE ADDRESS
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.
A change in information in the PCED TLV MUST NOT trigger any SPF
computation at a receiving router.
The way PCEs determine the information they advertise is out of the
scope of this document. Some information may be configured on the PCE
(e.g., address, preferences, scope) and other information may be
automatically determined by the PCE (e.g., areas of visibility).
6. Backward Compatibility
The PCED TLV defined in this document does not introduce any
interoperability issues.
A router not supporting the PCED TLV will just silently ignore the
TLV as specified in [OSPF-CAP].
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 13]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
7. IANA Considerations
7.1. OSPF TLV
IANA has defined a registry for TLVs carried in the Router
Information LSA defined in [OSPF-CAP]. IANA is requested to assign a
new TLV code-point for the PCED TLV carried within the Router
Information LSA.
Value TLV Name Reference
----- -------- ----------
5 PCED (this document)
7.2. PCE Capability Flags registry
This document provides new capability bit flags, which are present
in the PCE-CAP-FLAGS TLV referenced in section 4.1.5.
The IANA is requested to create a new top-level OSPF registry, the
"PCE Capability Flags" registry, and to manage the space of PCE
capability bit flags numbering them in the usual IETF notation
starting at zero and continuing at least through 31, with the most
significant bit as bit zero.
New bit numbers may be allocated only by an IETF Consensus action.
Each bit should be tracked with the following qualities:
- Bit number
- Capability Description
- Defining RFC
Several bits are defined in this document. Here are the suggested
values:
Bit Capability Description
0 Path computation with GMPLS link constraints
1 Bidirectional path computation
2 Diverse path computation
3 Load-balanced path computation
4 Synchronized paths computation
5 Support for multiple objective functions
6 Support for additive path constraints
(max hop count, etc.)
7 Support for request prioritization
8 Support for multiple requests per message
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 14]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
8. Security Considerations
This document defines OSPF extensions for PCE discovery within an
administrative domain. Hence the security of the PCE discovery relies
on the security of OSPF.
Mechanisms defined to ensure authenticity and integrity of OSPF LSAs
[RFC2154], and their TLVs, can be used to secure the PCE Discovery
information as well.
OSPF provides no encryption mechanism for protecting the privacy of
LSAs, and in particular the privacy of the PCE discovery information.
9. Manageability Considerations
Manageability considerations for PCE Discovery are addressed in
Section 4.10 of [RFC4674].
9.1. Control of Policy and Functions
Requirements for the configuration of PCE discovery parameters on
PCCs and PCEs are discussed in Section 4.10.1 of [RFC4674].
In particular, a PCE implementation SHOULD allow the following
parameters to be configured on the PCE:
- The PCE IPv4/IPv6 address(es) (see Section 4.1)
- The PCE Scope, including the inter-domain functions (inter-
area, inter-AS, inter-layer), the preferences, and whether the
PCE can act as default PCE (see Section 4.2)
- The PCE domains (see Section 4.3)
- The neighbour PCE domains (see Section 4.4)
- The PCE capabilities (see Section 4.5)
9.2. Information and Data Model
A MIB module for PCE Discovery is defined in [PCED-MIB].
9.3. Liveness Detection and Monitoring
PCE Discovery Protocol liveness detection relies upon OSPF liveness
detection. OSPF already includes a liveness detection mechanism
(Hello protocol), and PCE discovery does not require additional
capabilities.
Procedures defined in Section 5 allow a PCC to detect when a PCE has
been deactivated, or is no longer reachable.
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 15]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
9.4. Verify Correct Operations
The correlation of information advertised against information
received can be achieved by comparing the information in the PCED TLV
received by the PCC with that stored at the PCE using the PCED MIB
[PCED-MIB]. The number of dropped, corrupt, and rejected information
elements are available through the PCED MIB.
9.5. Requirements on Other Protocols and Functional Components
The OSPF extensions defined in this document do not imply any
requirement on other protocols.
9.6. Impact on Network Operations
Frequent changes in PCE information advertised in the PCED TLV, may
have a significant impact on OSPF and might destabilize the operation
of the network by causing the PCCs to swap between PCEs.
As discussed in Section 4.10.4 of [RFC4674], it MUST be possible to
apply at least the following controls:
- Configurable limit on the rate of announcement of changed
parameters at a PCE.
- Control of the impact on PCCs such as through rate-limiting
the processing of PCED TLVs.
- Configurable control of triggers that cause a PCC to swap to
another PCE.
10. Acknowledgments
We would like to thank Lucy Wong, Adrian Farrel, Les Ginsberg, Mike
Shand, and Lou Berger for their useful comments and suggestions.
We would also like to thank Dave Ward, Lars Eggert, Sam Hartman, and
Tim Polk for their comments during the final stages of publication.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2328] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[RFC2740] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",
RFC 2740, December 1999.
[RFC2370] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, July
1998.
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 16]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
[RFC3630] Katz, D., Yeung, D., Kompella, K., "Traffic Engineering
Extensions to OSPF Version 2", RFC 3630, September 2003.
[OSPF-CAP] Lindem, A., Shen, N., Aggarwal, R., Shaffer, S., Vasseur,
J.P., "Extensions to OSPF for advertising Optional Router
Capabilities", draft-ietf-ospf-cap, work in progress.
[RFC2154] Murphy, S., Badger, M., and B. Wellington, "OSPF with
Digital Signatures", RFC 2154, June 1997.
11.2. Informative References
[RFC4657] Ash, J., Le Roux, J.L., "PCE Communication Protocol Generic
Requirements", RFC4657, September 2006.
[PCEP] Vasseur, Le Roux, et al., "Path Computation Element (PCE)
communication Protocol (PCEP) - Version 1", draft-ietf-pce-pcep, work
in progress.
[PCED-MIB] Stephan, E., "Definitions of Managed Objects for Path
Computation Element Discovery", draft-ietf-pce-disc-mib, work in
progress.
[PCED-ISIS] Le Roux, Vasseur, et al. "IS-IS protocol extensions for
Path Computation Element (PCE) Discovery", draft-ietf-pce-disco-
proto-isis, work in progress.
[RFC4655] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation
Element (PCE)-based Architecture", RFC4655, August 2006.
[RFC4674] Le Roux, J.L., et al. "Requirements for PCE discovery",
RFC4674, October 2006.
12. Editor's Addresses
Jean-Louis Le Roux (Editor)
France Telecom
2, avenue Pierre-Marzin
22307 Lannion Cedex
FRANCE
Email: jeanlouis.leroux@orange-ftgroup.com
Jean-Philippe Vasseur (Editor)
Cisco Systems, Inc.
1414 Massachusetts avenue
Boxborough , MA - 01719
USA
Email: jpv@cisco.com
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 17]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
13. Contributors' Addresses
Yuichi Ikejiri
NTT Communications Corporation
1-1-6, Uchisaiwai-cho, Chiyoda-ku
Tokyo 100-8019
JAPAN
Email: y.ikejiri@ntt.com
Raymond Zhang
BT Infonet
2160 E. Grand Ave.
El Segundo, CA 90025
USA
Email: raymond_zhang@bt.infonet.com
14. Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided
on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE
IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 18]
Internet Draft draft-ietf-pce-disco-proto-ospf-08.txt October 2007
WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE
ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The IETF Trust (2007). This document is subject to the
rights, licenses and restrictions contained in BCP 78, and except as
set forth therein, the authors retain all their rights.
Le Roux, Vasseur et al. OSPF extensions for PCE Discovery [Page 19]