< draft-ietf-pce-disco-proto-ospf-07.txt   draft-ietf-pce-disco-proto-ospf-08.txt >
Network Working Group J.L. Le Roux (Editor) Network Working Group J.L. Le Roux (Editor)
Internet Draft France Telecom Internet Draft France Telecom
Intended Status: Standard Track Intended Status: Standard Track
Expires: March 2008 J.P. Vasseur (Editor) Expires: April 2008 J.P. Vasseur (Editor)
Cisco System Inc. Cisco System Inc.
Yuichi Ikejiri Yuichi Ikejiri
NTT Communications NTT Communications
Raymond Zhang Raymond Zhang
BT Infonet BT Infonet
September 2007 October 2007
OSPF protocol extensions for Path Computation Element (PCE) Discovery OSPF Protocol Extensions for Path Computation Element (PCE) Discovery
draft-ietf-pce-disco-proto-ospf-07.txt draft-ietf-pce-disco-proto-ospf-08.txt
Status of this Memo Status of this Memo
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aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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skipping to change at page 2, line 9 skipping to change at page 2, line 9
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). All rights reserved. Copyright (C) The IETF Trust (2007). All rights reserved.
Abstract Abstract
There are various circumstances where it is highly desirable for a There are various circumstances where it is highly desirable for a
Path Computation Client (PCC) to be able to dynamically and Path Computation Client (PCC) to be able to dynamically and
automatically discover a set of Path Computation Elements (PCE), automatically discover a set of Path Computation Elements (PCEs),
along with some information that can be used for PCE selection. When along with information that can be used by the PCC for PCE selection.
the PCE is a Label Switching Router (LSR) participating in the When the PCE is a Label Switching Router (LSR) participating in the
Interior Gateway Protocol (IGP), or even a server participating Interior Gateway Protocol (IGP), or even a server participating
passively in the IGP, a simple and efficient way to discover PCEs passively in the IGP, a simple and efficient way to announce PCEs
consists of using IGP flooding. For that purpose, this document consists of using IGP flooding. For that purpose, this document
defines extensions to the Open Shortest Path First (OSPF) routing defines extensions to the Open Shortest Path First (OSPF) routing
protocol for the advertisement of PCE Discovery information within an protocol for the advertisement of PCE Discovery information within an
OSPF area or within the entire OSPF routing domain. OSPF area or within the entire OSPF routing domain.
Conventions used in this document Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Table of Contents Table of Contents
1. Terminology.................................................3 1. Terminology.................................................3
2. Introduction................................................4 2. Introduction................................................4
3. Overview....................................................5 3. Overview....................................................5
3.1. PCE Information.............................................5 3.1. PCE Discovery Information...................................5
3.2. PCE Discovery Information...................................5 3.2. Flooding Scope..............................................5
3.2.1. PCE Overload Information....................................5
3.3. Flooding Scope..............................................6
4. The OSPF PCED TLV...........................................6 4. The OSPF PCED TLV...........................................6
4.1. PCE-ADDRESS Sub-TLV.........................................7 4.1. PCE-ADDRESS Sub-TLV.........................................7
4.2. PATH-SCOPE Sub-TLV..........................................8 4.2. PATH-SCOPE Sub-TLV..........................................8
4.3. PCE-DOMAIN Sub-TLV.........................................10 4.3. PCE-DOMAIN Sub-TLV.........................................10
4.4. NEIG-PCE-DOMAIN Sub-TLV....................................11 4.4. NEIG-PCE-DOMAIN Sub-TLV....................................11
4.5. PCE-CAP-FLAGS Sub-TLV......................................12 4.5. PCE-CAP-FLAGS Sub-TLV......................................11
4.6. The OVERLOAD Sub-TLV.......................................13 5. Elements of Procedure......................................13
5. Elements of Procedure......................................14 6. Backward Compatibility.....................................13
5.1. OVERLOAD sub-TLV Specific Procedures.......................14 7. IANA Considerations........................................14
6. Backward Compatibility.....................................15 7.1. OSPF TLV...................................................14
7. IANA Considerations........................................15 7.2. PCE Capability Flags registry..............................14
7.1. OSPF TLV...................................................15 8. Security Considerations....................................15
7.2. PCE Capability Flags registry..............................15 9. Manageability Considerations...............................15
8. Security Considerations....................................16 9.1. Control of Policy and Functions............................15
9. Manageability Considerations...............................16 9.2. Information and Data Model.................................15
9.1. Control of Policy and Functions............................16 9.3. Liveness Detection and Monitoring..........................15
9.2. Information and Data Model.................................17 9.4. Verify Correct Operations..................................16
9.3. Liveness Detection and Monitoring..........................17
9.4. Verify Correct Operations..................................17
9.5. Requirements on Other Protocols and Functional 9.5. Requirements on Other Protocols and Functional
Components...............................................17 Components...............................................16
9.6. Impact on network operations...............................17 9.6. Impact on Network Operations...............................16
10. Acknowledgments............................................18 10. Acknowledgments............................................16
11. References.................................................18 11. References.................................................16
11.1. Normative references.......................................18 11.1. Normative References.......................................16
11.2. Informative references.....................................18 11.2. Informative References.....................................17
12. Editor's Addresses.........................................19 12. Editor's Addresses.........................................17
13. Contributors' Addresses....................................19 13. Contributors' Addresses....................................18
14. Intellectual Property Statement............................19 14. Intellectual Property Statement............................18
1. Terminology 1. Terminology
ABR: OSPF Area Border Router. ABR: OSPF Area Border Router.
AS: Autonomous System. AS: Autonomous System.
IGP: Interior Gateway Protocol. Either of the two routing IGP: Interior Gateway Protocol. Either of the two routing
protocols Open Shortest Path First (OSPF) or Intermediate System protocols Open Shortest Path First (OSPF) or Intermediate System
to Intermediate System (ISIS). to Intermediate System (ISIS).
Intra-area TE LSP: A TE LSP whose path does not cross IGP area Intra-area TE LSP: A TE LSP whose path does not cross an IGP area
boundaries. boundary.
Intra-AS TE LSP: A TE LSP whose path does not cross AS boundaries. 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 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 areas. That is a TE LSP that crosses at least one IGP area
boundary. boundary.
Inter-AS TE LSP: A TE LSP whose path transits two or more 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 ASes or sub-ASes (BGP confederations). That is a TE LSP that
crosses at least one AS boundary. crosses at least one AS boundary.
LSA: Link State Advertisement LSA: Link State Advertisement.
LSR: Label Switching Router. LSR: Label Switching Router.
PCC: Path Computation Client: Any client application requesting a PCC: Path Computation Client. Any client application requesting a
path computation to be performed by a Path Computation Element. path computation to be performed by a Path Computation Element.
PCE: Path Computation Element: An entity (component, application, PCE: Path Computation Element. An entity (component, application,
or network node) that is capable of computing a network path or or network node) that is capable of computing a network path or
route based on a network graph, and applying computational route based on a network graph, and applying computational
constraints. constraints.
PCE-Domain: In a PCE context this refers to any collection of PCE-Domain: In a PCE context this refers to any collection of
network elements within a common sphere of address management or network elements within a common sphere of address management or
path computational responsibility (referred to as "domain" in path computational responsibility (referred to as a "domain" in
[RFC4655]). Examples of PCE-Domains include IGP areas and ASes. [RFC4655]). Examples of PCE-Domains include IGP areas and ASes.
This should be distinguished from an OSPF routing domain. This should be distinguished from an OSPF routing domain.
PCEP: Path Computation Element Protocol. PCEP: Path Computation Element Protocol.
TE LSP: Traffic Engineered Label Switched Path. TE LSP: Traffic Engineered Label Switched Path.
2. Introduction 2. Introduction
[RFC4655] describes the motivations and architecture for a PCE-based [RFC4655] describes the motivations and architecture for a Path
path computation model for Multi Protocol Label Switching (MPLS) and Computation Element (PCE)-based
Generalized MPLS (GMPLS) Traffic Engineered Label Switched Paths (TE- 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 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) Computation Client (PCC) (also referred to as a non co-located PCE)
and allows for cooperation between PCEs. This relies on a and allows for cooperation between PCEs (where one PCE acts as a PCC
communication protocol between PCC and PCE, and between PCEs. The to make requests of the other PCE). This relies on a communication
requirements for such a communication protocol can be found in protocol between PCC and PCE, and also between PCEs. The requirements
[RFC4657] and the communication protocol is defined in [PCEP]. 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 The PCE architecture requires that a PCC be aware of the location of
one or more PCEs in its domain, and also potentially of some PCEs in one or more PCEs in its domain, and also, potentially, of PCEs in
other domains, e.g. in case of inter-domain TE LSP computation. other domains, e.g., in the case of inter-domain TE LSP computation.
A network may contain a large number of PCEs with potentially A network may contain a large number of PCEs, each with potentially
distinct capabilities. In such a context it is highly desirable to distinct capabilities. In such a context it is highly desirable to
have a mechanism for automatic and dynamic PCE discovery, which have a mechanism for automatic and dynamic PCE discovery that allows
allows PCCs to automatically discover a set of PCEs, along with PCCs to automatically discover a set of PCEs along with additional
additional information about each PCE that may be required for the information about each PCE that may be used by a PCC to perform PCE
PCC to perform PCE selection. Additionally, it is valuable for a PCC selection. Additionally, it is valuable for a PCC to dynamically
to dynamically detect new PCEs or any modification of the PCE detect new PCEs, failed PCEs, or any modification to the PCE
information. Detailed requirements for such a PCE discovery mechanism information. Detailed requirements for such a PCE discovery mechanism
are provided in [RFC4674]. are provided in [RFC4674].
Moreover, it may also be useful to discover when a PCE experiences Note that the PCE selection algorithm applied by a PCC is out of the
processing overload and when it exits such a state, in order for the scope of this document.
PCCs to take some appropriate actions (e.g. to redirect their
requests to another PCE). 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 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 are either LSRs or servers also participating in the IGP, an
effective mechanism for PCE discovery within an IGP routing domain effective mechanism for PCE discovery within an IGP routing domain
consists of utilizing IGP advertisements. consists of utilizing IGP advertisements.
This document defines OSPF extensions to allow a PCE in an OSPF This document defines extensions to OSPFv2 [RFC2328] and OSPFv3
routing domain to advertise its location along with some information [RFC2740] to allow a PCE in an OSPF routing domain to advertise its
useful to a PCC for PCE selection so as to satisfy dynamic PCE location along with some information useful to a PCC for PCE
discovery requirements set forth in [RFC4674]. This document also selection so as to satisfy dynamic PCE discovery requirements set
defines extensions allowing a PCE in an OSPF routing domain to forth in [RFC4674].
advertise its overload state.
Generic capability advertisement mechanisms for OSPF are defined in Generic capability advertisement mechanisms for OSPF are defined in
[OSPF-CAP]. These allow a router to advertise its capabilities within [OSPF-CAP]. These allow a router to advertise its capabilities within
an OSPF area or an entire OSPF routing domain. This document an OSPF area or an entire OSPF routing domain. This document
leverages this generic capability advertisement mechanism to fully leverages this generic capability advertisement mechanism to fully
satisfy the aforementioned dynamic PCE discovery requirements. satisfy the dynamic PCE discovery requirements.
This document defines a new TLV (named the PCE Discovery (PCED) TLV) This document defines a new TLV (named the PCE Discovery (PCED) TLV)
to be carried within the OSPF Router Information LSA ([OSPF-CAP]). to be carried within the OSPF Router Information LSA ([OSPF-CAP]).
The PCE information advertised is detailed in section 3. Protocol The PCE information advertised is detailed in Section 3. Protocol
extensions and procedures are defined in section 4 and 5. extensions and procedures are defined in Sections 4 and 5.
The OSPF extensions defined in this document allow for PCE discovery The OSPF extensions defined in this document allow for PCE discovery
within an OSPF Routing domain. Solutions for PCE discovery across AS within an OSPF routing domain. Solutions for PCE discovery across AS
boundaries are beyond the scope of this document, and for further boundaries are beyond the scope of this document, and for further
study. study.
3. Overview 3. Overview
3.1. PCE Information 3.1. PCE Discovery Information
The PCE information advertised via OSPF falls into two categories:
PCE Discovery information and PCE Overload information.
3.2. PCE Discovery Information
The PCE Discovery information is comprised of: The PCE discovery information is composed of:
- The PCE location: an IPv4 and/or IPv6 address that is used to reach - 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 the PCE. It is RECOMMENDED to use an address that is always
reachable; reachable if there is any connectivity to the PCE;
- The PCE path computation scope (i.e. inter-area, inter-AS, inter- - The PCE path computation scope (i.e., intra-area, inter-area,
layer); inter-AS, or inter-layer);
- The set of one or more PCE-Domain(s) into which the PCE has - The set of one or more PCE-Domain(s) into which the PCE has
visibility and can compute paths; visibility and for which the PCE can compute paths;
- The set of one or more neighbor PCE-Domain(s) towards which a PCE - The set of zero, one or more neighbor PCE-Domain(s) toward which
can compute paths; the PCE can compute paths;
- A set of communication capabilities (e.g. support for request - A set of communication capabilities (e.g., support for request
prioritization) and path computation specific capabilities prioritization) and path computation-specific capabilities
(e.g. supported constraints). (e.g., supported constraints).
PCE Discovery information is by nature fairly static and does not PCE discovery information is by nature fairly static and does not
change with PCE activity. Changes in PCE Discovery information may change with PCE activity. Changes in PCE discovery information may
occur as a result of PCE configuration updates, PCE occur as a result of PCE configuration updates, PCE
deployment/activation, PCE deactivation/suppression, or PCE failure. deployment/activation, PCE deactivation/suppression, or PCE failure.
Hence, this information is not expected to change frequently. Hence, this information is not expected to change frequently.
3.2.1. PCE Overload Information 3.2. Flooding Scope
The PCE Overload information is optional and can be used to report a
PCE's overload state in order to discourage the PCCs to send new path
computation requests.
A PCE may decide to clear the overload state according to local
implementation triggers (e.g. CPU utilization, average queue length
below some predefined thresholds). The rate at which a PCE Status
change is advertised MUST NOT impact by any means the IGP
scalability. Particular attention MUST be given on procedures to
avoid state oscillations.
3.3. Flooding Scope
The flooding scope for PCE information advertised through OSPF can be 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 limited to one or more OSPF areas the PCE belongs to, or can be
extended across the entire OSPF routing domain. extended across the entire OSPF routing domain.
Note that some PCEs may belong to multiple areas, in which case the 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 flooding scope may comprise these areas. This could be the case for
an ABR for instance advertising its PCE information within the an ABR, for instance, advertising its PCE information within the
backbone area and/or a subset of its attached IGP area(s). backbone area and/or a subset of its attached IGP area(s).
4. The OSPF PCED TLV 4. The OSPF PCED TLV
The OSPF PCE Discovery TLV (PCED TLV) is made of a set of non-ordered The OSPF PCE Discovery TLV (PCED TLV) contains non-ordered set of
sub-TLVs. sub-TLVs.
The format of the OSPF PCED TLV and its sub-TLVs is identical to the 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 TLV format used by the Traffic Engineering Extensions to OSPF
[RFC3630]. That is, the TLV is comprised of 2 octets for the type, 2 [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 octets specifying the TLV length, and a value field. The Length field
defines the length of the value portion in octets. defines the length of the value portion in octets.
The TLV is padded to four-octet alignment; padding is not included in 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 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 three, but the total size of the TLV would be eight octets). Nested
TLVs are also four-octet aligned. Unrecognized types are ignored. TLVs are also four-octet aligned. Unrecognized types are ignored.
The OSPF PCED TLV has the following format: The OSPF PCED TLV has the following format:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
// sub-TLVs // // sub-TLVs //
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type To be defined by IANA (suggested value=5) Type To be defined by IANA (suggested value=5)
Length Variable Length Variable
Value This comprises one or more sub-TLVs Value This comprises one or more sub-TLVs
Six sub-TLVs are defined: Five sub-TLVs are defined:
Sub-TLV type Length Name Sub-TLV type Length Name
1 variable PCE-ADDRESS sub-TLV 1 variable PCE-ADDRESS sub-TLV
2 4 PATH-SCOPE sub-TLV 2 4 PATH-SCOPE sub-TLV
3 variable PCE-DOMAIN sub-TLV 3 4 PCE-DOMAIN sub-TLV
4 variable NEIG-PCE-DOMAIN sub-TLV 4 4 NEIG-PCE-DOMAIN sub-TLV
5 variable PCE-CAP-FLAGS sub-TLV 5 variable PCE-CAP-FLAGS sub-TLV
6 4 OVERLOAD sub-TLV
The PCE-ADDRESS and PATH-SCOPE sub-TLVs MUST always be present within The PCE-ADDRESS and PATH-SCOPE sub-TLVs MUST always be present within
the PCED TLV. the PCED TLV.
The PCE-DOMAIN and NEIG-PCE-DOMAIN sub-TLVs are optional. They MAY be 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. 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 The PCE-CAP-FLAGS sub-TLV is optional and MAY be present in the PCED
TLV to facilitate the PCE selection process. TLV to facilitate the PCE selection process.
The OVERLOAD sub-TLV is optional and MAY be present in the PCED TLV, Malformed PCED TLVs or sub-TLVs not explicitly described in this
to indicate a PCE's overload state. document MUST cause the LSA to be treated as malformed according to
the normal procedures of OSPF.
Any non recognized sub-TLV MUST be silently ignored. Any unrecognized sub-TLV MUST be silently ignored.
The PCED TLV is carried within an OSPF Router Information LSA The PCED TLV is carried within an OSPF Router Information LSA
defined in [OSPF-CAP]. defined in [OSPF-CAP].
No additional sub-TLVs will be added to the PCED TLV in the future. No additional sub-TLVs will be added to the PCED TLV in the future.
If a future application requires advertising additional PCE If a future application requires the advertisement of additional PCE
information in OSPF, this will not be carried in the Router information in OSPF, this will not be carried in the Router
Information LSA. Information LSA.
The following sub-sections describe the sub-TLVs which may be carried The following sub-sections describe the sub-TLVs which may be carried
within the PCED sub-TLV. within the PCED sub-TLV.
4.1. PCE-ADDRESS Sub-TLV 4.1. PCE-ADDRESS Sub-TLV
The PCE-ADDRESS sub-TLV specifies the IP address(es) that can be 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 used to reach the PCE. It is RECOMMENDED to make use of an address
that is always reachable, provided that the PCE is alive. 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 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 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. address. It MUST NOT appear more than once for the same address type.
If it appears more than once, only the first occurrence MUST be If it appears more than once, only the first occurrence is processed
processed and other MUST be ignored. and any others MUST be ignored.
The format of the PCE-ADDRESS sub-TLV is as follows: The format of the PCE-ADDRESS sub-TLV is as follows:
1 2 3 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 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 | | Type = 1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| address-type | Reserved | | address-type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// PCE IP Address // // PCE IP Address //
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PCE-ADDRESS sub-TLV format PCE-ADDRESS sub-TLV format
Type 1 Type 1
Length 8 (IPv4) or 20 (IPv6) Length 8 (IPv4) or 20 (IPv6)
Address-type: Address-type:
1 IPv4 1 IPv4
2 IPv6 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. PCE IP Address: The IP address to be used to reach the PCE.
4.2. PATH-SCOPE Sub-TLV 4.2. PATH-SCOPE Sub-TLV
The PATH-SCOPE sub-TLV indicates the PCE path computation scope, 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 which refers to the PCE's ability to compute or take part in the
computation of intra-area, inter-area, inter-AS, or inter-layer_TE computation of paths for intra-area, inter-area, inter-AS, or inter-
LSP(s). layer_TE LSPs.
The PATH-SCOPE sub-TLV is mandatory; it MUST be present within the 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- 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 TLV within each PCED TLV. If it appears more than once, only the
first occurrence MUST be processed and other MUST be ignored. first occurrence is processed and any others MUST be ignored.
The PATH-SCOPE sub-TLV contains a set of bit flags indicating the The PATH-SCOPE sub-TLV contains a set of bit-flags indicating the
supported path scopes and four fields indicating PCE preferences. supported path scopes, and four fields indicating PCE preferences.
The PATH-SCOPE sub-TLV has the following format: The PATH-SCOPE sub-TLV has the following format:
1 2 3 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 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 | | Type = 2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|1|2|3|4|5| Reserved |PrefL|PrefR|PrefS|PrefY| Res | |0|1|2|3|4|5| Reserved |PrefL|PrefR|PrefS|PrefY| Res |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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1 R bit: Can act as PCE for inter-area TE LSP 1 R bit: Can act as PCE for inter-area TE LSP
computation computation
2 Rd bit: Can act as a default PCE for inter-area TE LSP 2 Rd bit: Can act as a default PCE for inter-area TE LSP
computation computation
3 S bit: Can act as PCE for inter-AS 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 4 Sd bit: Can act as a default PCE for inter-AS TE LSP
computation computation
5 Y bit: Can compute or take part into the computation 5 Y bit: Can compute or take part into the computation
of paths across layers. of paths across layers.
Pref-L field: PCE's preference for intra-area TE LSPs computation. PrefL field: PCE's preference for intra-area TE LSPs
computation.
Pref-R field: PCE's preference for inter-area TE LSPs computation. PrefR field: PCE's preference for inter-area TE LSPs
computation.
Pref-S field: PCE's preference for inter-AS TE LSPs computation. PrefS field: PCE's preference for inter-AS TE LSPs
computation.
Pref-Y field: PCE's preference for inter-layer TE LSPs computation. PrefY field: PCE's preference for inter-layer TE LSPs
computation.
Res: Reserved for future usage. Res: Reserved for future use.
The L, R, S, and Y bits are set when the PCE can act as a PCE for 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 intra-area, inter-area, inter-AS, or inter-layer TE LSPs computation
respectively. These bits are non-exclusive. respectively. These bits are non-exclusive.
When set the Rd bit indicates that the PCE can act as a default PCE 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 for inter-area TE LSPs computation (that is, the PCE can compute a
path towards any neighbor area). Similarly, when set, the Sd bit 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 indicates that the PCE can act as a default PCE for inter-AS TE LSP
computation (the PCE can compute a path towards any neighbor AS). 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 any When the Rd and Sd bit are set the PCED TLV MUST NOT contain a NEIG-
NEIG-PCE-DOMAIN sub-TLV (see 4.1.4). PCE-DOMAIN sub-TLV (see Section 4.1.4).
When the R/S bit is cleared, the Rd/Sd bit SHOULD be cleared and MUST When the R bit is clear, the Rd bit SHOULD be clear on transmission
be ignored. 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 The PrefL, PrefR, PrefS, and PrefY fields are each three bits long
allow the PCE to specify a preference for each computation scope, and allow the PCE to specify a preference for each computation scope,
where 7 reflects the highest preference. Such preference can be used where 7 reflects the highest preference. Such preferences can be used
for weighted load balancing of requests. An operator may decide to for weighted load balancing of path computation requests. An operator
configure a preference for each computation scope to each PCE so as may decide to configure a preference for each computation scope at
to balance the path computation load among them. The algorithms used each PCE so as to balance the path computation load among them. The
by a PCC to load balance its path computation requests according to algorithms used by a PCC to load balance its path computation
such PCE preference is out of the scope of this document and is a requests according to such PCE preferences is out of the scope of
matter for local or network wide policy. The same or distinct this document and is a matter for local or network-wide policy. The
preferences may be used for each scope. For instance an operator that same or different preferences may be used for each scope. For
wants a PCE capable of both inter-area and inter-AS computation to be instance, an operator that wants a PCE capable of both inter-area and
used preferably for inter-AS computation may configure a PrefS higher inter-AS computation to be prefered for use for inter-AS computations
than the PrefR. may configure PrefS higher than PrefR.
When the L bit, R bit, S bit or Y bit are cleared, the PrefL, PrefR, When the L, R, S, or Y bits are cleared, the PrefL, PrefR, PrefS, and
PrefS, PrefY fields SHOULD respectively be set to 0 and MUST be PrefY fields SHOULD respectively be set to 0 on transmission and MUST
ignored. be ignored on receipt.
Both reserved fields SHOULD be set to zero on transmission and MUST Both reserved fields SHOULD be set to zero on transmission and MUST
be ignored on receipt. be ignored on receipt.
4.3. PCE-DOMAIN Sub-TLV 4.3. PCE-DOMAIN Sub-TLV
The PCE-DOMAIN sub-TLV specifies a PCE-Domain (areas and/or ASes) The PCE-DOMAIN sub-TLV specifies a PCE-Domain (area or AS) where the
where the PCE has topology visibility and through which the PCE can PCE has topology visibility and through which the PCE can compute
compute paths. paths.
The PCE-DOMAIN sub-TLV MAY be present when PCE-Domains cannot be The PCE-DOMAIN sub-TLV SHOULD be present when PCE-Domains for which
inferred by other IGP information, for instance when the PCE is the PCE can operate cannot be inferred by other IGP information, for
inter-domain capable (i.e. when the R bit or S bit is set) and the instance when the PCE is inter-domain capable (i.e., when the R bit
flooding scope is the entire routing domain (see section 5 for a or S bit is set) and the flooding scope is the entire routing domain
discussion of how the flooding scope is set and interpreted). (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 A PCED TLV may include multiple PCE-DOMAIN sub-TLVs when the PCE has
visibility in multiple PCE-Domains. visibility into multiple PCE-Domains.
The PCE-DOMAIN sub-TLV has the following format: The PCE-DOMAIN sub-TLV has the following format:
1 2 3 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 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 | | Type=3 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain-type | Reserved | | Domain-type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | Domain ID |
// Domain ID //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PCE-DOMAIN sub-TLV format PCE-DOMAIN sub-TLV format
Type 3 Type 3
Length Variable Length 8
3 domain-type values are defined:
1 IPv4 Area Address
2 IPv6 Area Address
3 AS Number
Domain ID: With the address type 1/2 this indicates the IPv4/v6 Two domain-type values are defined:
address of an area where the PCE has visibility. With address- 1 OSPF Area ID
type 3 this indicates an AS number where the PCE has 2 AS Number
visibility. When coded in two octets (which is the current
defined format as the time of writing this document), the AS Domain ID: With the domain-type set to 1, this indicates the 32
Number field MUST have its first two octets set to 0. 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.
. .
4.4. NEIG-PCE-DOMAIN Sub-TLV 4.4. NEIG-PCE-DOMAIN Sub-TLV
The NEIG-PCE-DOMAIN sub-TLV specifies a neighbour PCE-domain (area, 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 AS) toward which a PCE can compute paths. It means that the PCE can
take part in the computation of inter-domain TE LSPs whose path take part in the computation of inter-domain TE LSPs with paths that
transits this neighbour PCE-domain. transit this neighbor PCE-domain.
A PCED sub-TLV MAY include several NEIG-PCE-DOMAIN sub-TLVs when the A PCED sub-TLV may include several NEIG-PCE-DOMAIN sub-TLVs when the
PCE can compute paths towards several neighbour PCE-domains. PCE can compute paths towards several neighbour PCE-domains.
The NEIG-PCE-DOMAIN sub-TLV has the same format as the PCE-DOMAIN The NEIG-PCE-DOMAIN sub-TLV has the same format as the PCE-DOMAIN
sub-TLV: sub-TLV:
1 2 3 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 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 | | Type = 4 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain-type | Reserved | | Domain-type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | Domain ID |
// Domain ID //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NEIG-PCE-DOMAIN sub-TLV format NEIG-PCE-DOMAIN sub-TLV format
Type 4 Type 4
Length Variable Length 8
3 domain-type values are defined: Two domain-type values are defined:
1 IPv4 Area Address 1 OSPF Area ID
2 IPv6 Area Address 2 AS Number
3 AS Number
Domain ID: With the address type 1/2 this indicates the Domain ID: With the domain-type set to 1, this indicates the 32
IPv4/v6 address of a neighbour area towards which the PCE can bit Area ID of a neighbour area toward which the PCE can
compute paths. With address-type 3 this indicates the AS number compute paths. With domain-type set to 2, this indicates the AS
of a neighbour AS towards which the PCE can compute paths. When number of a neighbor AS toward which the PCE can compute paths.
coded in two octets (which is the current defined format as the When the AS number is coded in two octets, the AS Number field
time of writing this document), the AS Number field MUST have MUST have its first two octets set to 0.
its first two octets set to 0.
The NEIG-PCE-DOMAIN sub-TLV MUST be present if the R bit is set and The NEIG-PCE-DOMAIN sub-TLV MUST be present at least once with
the Rd bit is cleared, and/or, if the S bit is set and the Sd bit is domain-type set to 1 if the R bit is set and the Rd bit is cleared,
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 4.5. PCE-CAP-FLAGS Sub-TLV
The PCE-CAP-FLAGS sub-TLV is an optional sub-TLV used to indicate PCE 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 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 present more than once. If it appears more than once, only the first
occurrence MUST be processed and other MUST be ignored. occurrence is processed and any others MUST be ignored.
The value field of the PCE-CAP-FLAGS sub-TLV is made up of an array The value field of the PCE-CAP-FLAGS sub-TLV is made up of an array
of units of 32 flags numbered from the most significant as bit zero, of units of 32 bit-flags numbered from the most significant bit as
where each bit represents one PCE capability. bit zero, where each bit represents one PCE capability.
The format of the PCE-CAP-FLAGS sub-TLV is as follows: The format of the PCE-CAP-FLAGS sub-TLV is as follows:
0 1 2 3 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 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 | | Type = 5 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
// PCE Capability Flags // // PCE Capability Flags //
skipping to change at page 13, line 4 skipping to change at page 12, line 28
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 5 Type 5
Length Multiple of 4 octets Length Multiple of 4 octets
Value This contains an array of units of 32 bit flags Value This contains an array of units of 32 bit flags
numbered from the most significant as bit zero, where numbered from the most significant as bit zero, where
each bit represents one PCE capability. each bit represents one PCE capability.
IANA is requested to manage the space of the PCE Capability Flags IANA is requested to manage the space of the PCE Capability Flags
The following bits are to be assigned by IANA: The following bits are to be assigned by IANA:
Bit Capabilities Bit Capabilities
0 Path computation with GMPLS link constraints 0 Path computation with GMPLS link constraints
1 Bidirectional path computation 1 Bidirectional path computation
2 Diverse path computation 2 Diverse path computation
3 Load-balanced path computation 3 Load-balanced path computation
4 Synchronized paths computation 4 Synchronized path computation
5 Support for multiple objective functions 5 Support for multiple objective functions
6 Support for additive path constraints 6 Support for additive path constraints
(max hop count, etc.) (max hop count, etc.)
7 Support for request prioritization 7 Support for request prioritization
8 Support for multiple requests per message 8 Support for multiple requests per message
9-31 Reserved for future assignments by IANA. 9-31 Reserved for future assignments by IANA.
These capabilities are defined in [RFC4657]. These capabilities are defined in [RFC4657].
Reserved bits SHOULD be set to zero on transmission and MUST be Reserved bits SHOULD be set to zero on transmission and MUST be
ignored on receipt. ignored on receipt.
4.6. The OVERLOAD Sub-TLV
The OVERLOAD sub-TLV is used to indicate that a PCE is experiencing
a processing overload state.
The OVERLOAD sub-TLV is optional, it MAY be carried within the PCED
TLV. It MUST NOT be present more than once. If it appears more than
once, only the first occurrence MUST be processed and other MUST be
ignored.
The format of the OVERLOAD 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 = 6 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 6
Length 4
Value
-C bit: When set this indicates that the PCE is overloaded
and cannot accept any new request. When cleared this
indicates that the PCE is not overloaded and can
accept new requests.
5. Elements of Procedure 5. Elements of Procedure
The PCED TLV is advertised within OSPFv2 Router Information LSAs The PCED TLV is advertised within OSPFv2 Router Information LSAs
(Opaque type of 4 and Opaque ID of 0) or OSPFv3 Router information (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, LSAs (function code of 12) which are defined in [OSPF-CAP]. As such,
elements of procedure are inherited from those defined in [OSPF-CAP]. elements of procedure are inherited from those defined in [OSPF-CAP].
In OSPFv2 the flooding scope is controlled by the opaque LSA type (as 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 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 [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 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 or an OSPFV3 Router Information LSA with the S1 bit set and the S2
bit cleared. If the flooding scope is the entire domain then the PCED bit clear. If the flooding scope is the entire IGP domain then the
TLV MUST be carried within an OSPFv2 type 11 Router Information LSA PCED TLV MUST be carried within an OSPFv2 type 11 Router Information
or OSPFv3 Router Information LSA with the S1 bit cleared and the S2 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 bit set. When only the L bit of the PATH-SCOPE sub-TLV is set, the
flooding scope MUST be area local. flooding scope MUST be area local.
An OSPF router MUST originate a new Router Information LSA whenever When the PCE function is deactivated, the OSPF speaker advertising
there is a change in a PCED TLV associated with a PCE it advertises. this PCE MUST originate a new Router Information LSA that no longer
includes the corresponding PCED TLV, provided there are other TLVs in
When a PCE is deactivated, the OSPF router advertising this PCE MUST the LSA. If there are no other TLVs in the LSA, it MUST either send
originate a new Router Information LSA that no longer includes the an empty Router Information LSA or purge it by prematurely aging it.
corresponding PCED TLV.
The PCE address, i.e. the address indicated within the PCE ADDRESS The PCE address (i.e., the address indicated within the PCE ADDRESS
TLV, SHOULD be reachable via some prefixes advertised by OSPF; this TLV) SHOULD be reachable via some prefixes advertised by OSPF. This
allows speeding up the detection of a PCE failure. Note that when the allows the detection of a PCE failure to be sped up. When the PCE
PCE address is no longer reachable, this means that the PCE node has address is no longer reachable, the PCE node has failed, has been
failed or has been torn down, or that there is no longer IP torn down, or there is no longer IP connectivity to the PCE.
connectivity to the PCE node.
A change in PCED information MUST NOT trigger any SPF computation at A change in information in the PCED TLV MUST NOT trigger any SPF
a receiving router. computation at a receiving router.
The way PCEs determine the information they advertise is out of the The way PCEs determine the information they advertise is out of the
scope of this document. Some information may be configured on the PCE scope of this document. Some information may be configured on the PCE
(e.g., address, preferences, scope) and other information may be (e.g., address, preferences, scope) and other information may be
automatically determined by the PCE (e.g., areas of visibility). automatically determined by the PCE (e.g., areas of visibility).
5.1. OVERLOAD sub-TLV Specific Procedures
When a PCE enters into an overload state, the conditions of which are
implementation dependent, a Router Information LSA with an OVERLOAD
sub-TLV with the C bit set MAY be generated.
When a PCE exits from an overload state, the conditions of which are
implementation dependent (e.g. CPU utilization, average queue length
below some pre-defined threshold), a new Router Information LSA with
an OVERLOAD sub-TLV with the C bit cleared SHOULD be generated, if
the overload information had been previously advertised.
A PCE implementation supporting the OSPF extensions defined in this
document SHOULD support an appropriate dampening algorithm so as to
dampen OSPF flooding of PCE Overload information in order to not
impact the OSPF scalability. It is RECOMMENDED to introduce some
hysteresis for overload state transition, so as to avoid state
oscillations that may impact OSPF performance. For instance two
thresholds MAY be configured: An upper-threshold and a lower-
threshold; an LSR enters the overload state when the CPU load reaches
the upper threshold and leaves the overload state when the CPU load
goes under the lower threshold.
Upon receipt of an updated OVERLOAD sub-TLV a PCC SHOULD take
appropriate actions. In particular, the PCC SHOULD stop sending
requests to an overloaded PCE, and SHOULD gradually start sending
again requests to a PCE that is no longer overloaded.
6. Backward Compatibility 6. Backward Compatibility
The PCED TLV defined in this document does not introduce any The PCED TLV defined in this document does not introduce any
interoperability issues. interoperability issues.
A router not supporting the PCED TLV will just silently ignore the A router not supporting the PCED TLV will just silently ignore the
TLV as specified in [OSPF-CAP]. TLV as specified in [OSPF-CAP].
7. IANA Considerations 7. IANA Considerations
7.1. OSPF TLV 7.1. OSPF TLV
Once the OSPF RI TLVs registry defined in [OSPF-CAP] will have been IANA has defined a registry for TLVs carried in the Router
assigned, IANA will assign a new TLV code-point for the PCED TLV Information LSA defined in [OSPF-CAP]. IANA is requested to assign a
carried within the Router Information LSA. new TLV code-point for the PCED TLV carried within the Router
Information LSA.
Value TLV Name Reference Value TLV Name Reference
----- -------- ---------- ----- -------- ----------
5 PCED (this document) 5 PCED (this document)
7.2. PCE Capability Flags registry 7.2. PCE Capability Flags registry
This document provides new capability bit flags, which are present This document provides new capability bit flags, which are present
in the PCE-CAP-FLAGS TLV referenced in section 4.1.5. in the PCE-CAP-FLAGS TLV referenced in section 4.1.5.
skipping to change at page 16, line 45 skipping to change at page 15, line 21
Mechanisms defined to ensure authenticity and integrity of OSPF LSAs Mechanisms defined to ensure authenticity and integrity of OSPF LSAs
[RFC2154], and their TLVs, can be used to secure the PCE Discovery [RFC2154], and their TLVs, can be used to secure the PCE Discovery
information as well. information as well.
OSPF provides no encryption mechanism for protecting the privacy of OSPF provides no encryption mechanism for protecting the privacy of
LSAs, and in particular the privacy of the PCE discovery information. LSAs, and in particular the privacy of the PCE discovery information.
9. Manageability Considerations 9. Manageability Considerations
Manageability considerations for PCE Discovery are addressed in Manageability considerations for PCE Discovery are addressed in
section 4.10 of [RFC4674]. Section 4.10 of [RFC4674].
9.1. Control of Policy and Functions 9.1. Control of Policy and Functions
Requirements on the configuration of PCE discovery parameters on PCCs Requirements for the configuration of PCE discovery parameters on
and PCEs are discussed in section 4.10.1 of [RFC4674]. PCCs and PCEs are discussed in Section 4.10.1 of [RFC4674].
Particularly, a PCE implementation SHOULD allow configuring the In particular, a PCE implementation SHOULD allow the following
following parameters on the PCE: parameters to be configured on the PCE:
-The PCE IPv4/IPv6 address(es) (see section 4.1.1) - The PCE IPv4/IPv6 address(es) (see Section 4.1)
-The PCE Scope, including the inter-domain functions (inter- - The PCE Scope, including the inter-domain functions (inter-
area, inter-AS, inter-layer), the preferences, and whether the area, inter-AS, inter-layer), the preferences, and whether the
PCE can act as default PCE (see section 4.1.2) PCE can act as default PCE (see Section 4.2)
-The PCE domains (see section 4.1.3) - The PCE domains (see Section 4.3)
-The neighbour PCE domains (see section 4.1.4) - The neighbour PCE domains (see Section 4.4)
-The PCE capabilities (see section 4.1.5) - The PCE capabilities (see Section 4.5)
9.2. Information and Data Model 9.2. Information and Data Model
A MIB module for PCE Discovery is defined in [PCED-MIB]. A MIB module for PCE Discovery is defined in [PCED-MIB].
9.3. Liveness Detection and Monitoring 9.3. Liveness Detection and Monitoring
PCE Discovery Protocol liveness detection relies upon OSPF liveness PCE Discovery Protocol liveness detection relies upon OSPF liveness
detection. OSPF already includes a liveness detection mechanism detection. OSPF already includes a liveness detection mechanism
(Hello protocol), and PCE discovery does not require additional (Hello protocol), and PCE discovery does not require additional
capabilities. capabilities.
Procedures defined in section 5.1 allow a PCC detecting when a PCE Procedures defined in Section 5 allow a PCC to detect when a PCE has
has been deactivated, or is no longer reachable. been deactivated, or is no longer reachable.
9.4. Verify Correct Operations 9.4. Verify Correct Operations
The correlation of information advertised against information The correlation of information advertised against information
received can be achieved by comparing the PCED information in the PCC received can be achieved by comparing the information in the PCED TLV
and in the PCE, which is stored in the PCED MIB [PCED-MIB]. The received by the PCC with that stored at the PCE using the PCED MIB
number of dropped, corrupt, and rejected information elements are [PCED-MIB]. The number of dropped, corrupt, and rejected information
stored in the PCED MIB. elements are available through the PCED MIB.
9.5. Requirements on Other Protocols and Functional Components 9.5. Requirements on Other Protocols and Functional Components
The OSPF extensions defined in this document do not imply any The OSPF extensions defined in this document do not imply any
requirement on other protocols. requirement on other protocols.
9.6. Impact on network operations 9.6. Impact on Network Operations
Frequent changes in PCE information, and particularly in PCE overload
information, 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 5.1, a PCE implementation SHOULD support an Frequent changes in PCE information advertised in the PCED TLV, may
appropriate dampening algorithm so as to dampen OSPF flooding in have a significant impact on OSPF and might destabilize the operation
order to not impact the OSPF scalability. of the network by causing the PCCs to swap between PCEs.
Also, as discussed in section 4.10.4 of [RFC4674], it MUST be As discussed in Section 4.10.4 of [RFC4674], it MUST be possible to
possible to apply at least the following controls: apply at least the following controls:
- Configurable limit on the rate of announcement of changed - Configurable limit on the rate of announcement of changed
parameters at a PCE. parameters at a PCE.
- Control of the impact on PCCs such as through discovery messages - Control of the impact on PCCs such as through rate-limiting
rate-limiting. the processing of PCED TLVs.
- Configurable control of triggers that cause a PCC to swap to - Configurable control of triggers that cause a PCC to swap to
another PCE. another PCE.
10. Acknowledgments 10. Acknowledgments
We would like to thank Lucy Wong, Adrian Farrel, Les Ginsberg, Mike We would like to thank Lucy Wong, Adrian Farrel, Les Ginsberg, Mike
Shand and Lou Berger for their useful comments and suggestions. Shand, and Lou Berger for their useful comments and suggestions.
We would also like to thank Dave Ward, Lars Eggert, Sam Hartman, and We would also like to thank Dave Ward, Lars Eggert, Sam Hartman, and
Tim Polk for their comments during the final stages of publication. Tim Polk for their comments during the final stages of publication.
11. References 11. References
11.1. Normative references 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. 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", [RFC2740] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",
RFC 2740, December 1999. RFC 2740, December 1999.
[RFC2370] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, July [RFC2370] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, July
1998. 1998.
[RFC3630] Katz, D., Yeung, D., Kompella, K., "Traffic Engineering [RFC3630] Katz, D., Yeung, D., Kompella, K., "Traffic Engineering
Extensions to OSPF Version 2", RFC 3630, September 2003. Extensions to OSPF Version 2", RFC 3630, September 2003.
[OSPF-CAP] Lindem, A., Shen, N., Aggarwal, R., Shaffer, S., Vasseur, [OSPF-CAP] Lindem, A., Shen, N., Aggarwal, R., Shaffer, S., Vasseur,
J.P., "Extensions to OSPF for advertising Optional Router J.P., "Extensions to OSPF for advertising Optional Router
Capabilities", draft-ietf-ospf-cap, work in progress. Capabilities", draft-ietf-ospf-cap, work in progress.
[RFC2154] Murphy, S., Badger, M., and B. Wellington, "OSPF with [RFC2154] Murphy, S., Badger, M., and B. Wellington, "OSPF with
Digital Signatures", RFC 2154, June 1997. Digital Signatures", RFC 2154, June 1997.
11.2. Informative references 11.2. Informative References
[RFC4657] Ash, J., Le Roux, J.L., "PCE Communication Protocol Generic [RFC4657] Ash, J., Le Roux, J.L., "PCE Communication Protocol Generic
Requirements", RFC4657, September 2006. Requirements", RFC4657, September 2006.
[PCEP] Vasseur, Le Roux, et al., "Path Computation Element (PCE) [PCEP] Vasseur, Le Roux, et al., "Path Computation Element (PCE)
communication Protocol (PCEP) - Version 1", draft-ietf-pce-pcep, work communication Protocol (PCEP) - Version 1", draft-ietf-pce-pcep, work
in progress. in progress.
[PCED-MIB] Stephan, E., "Definitions of Managed Objects for Path [PCED-MIB] Stephan, E., "Definitions of Managed Objects for Path
Computation Element Discovery", draft-ietf-pce-disc-mib, work in Computation Element Discovery", draft-ietf-pce-disc-mib, work in
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