draft-ietf-pce-disco-proto-isis-02.txt   draft-ietf-pce-disco-proto-isis-03.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
Category: Standard Track Category: Standard Track
Expires: August 2007 J.P. Vasseur (Editor) Expires: October 2007 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
February 2007
IS-IS protocol extensions for Path Computation Element (PCE) Discovery IS-IS protocol extensions for Path Computation Element (PCE) Discovery
draft-ietf-pce-disco-proto-isis-02.txt draft-ietf-pce-disco-proto-isis-03.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware 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 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. 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
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
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http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
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 (PCE),
along with some of information that can be used for PCE selection. along with some information that can be used for PCE selection. When
When the PCE is a Label Switching Router (LSR) participating in the 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 discover 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 Intermediate System to Intermediate System defines extensions to the Intermediate System to Intermediate System
(IS-IS) routing protocol for the advertisement of PCE Discovery (IS-IS) routing protocol for the advertisement of PCE Discovery
information within an IS-IS area or within the entire IS-IS routing information within an IS-IS area or within the entire IS-IS routing
domain. domain.
Conventions used in this document Conventions used in this document
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"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 RFC-2119. document are to be interpreted as described in RFC-2119.
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 Information.............................................5
3.1.1. PCE Discovery Information...................................5 3.1.1. PCE Discovery Information...................................5
3.1.2. PCE Status Information......................................6 3.1.2. PCE Congestion Information..................................6
3.2. Flooding scope..............................................6 3.2. Flooding scope..............................................6
4. IS-IS extensions............................................6 4. IS-IS extensions............................................7
4.1. The IS-IS PCED TLV..........................................6 4.1. The IS-IS PCED sub-TLV......................................7
4.1.1. PCE-ADDRESS sub-TLV.........................................7 4.1.1. PCE-ADDRESS sub-TLV.........................................8
4.1.2. The PATH-SCOPE sub-TLV......................................8 4.1.2. The PATH-SCOPE sub-TLV......................................8
4.1.3. PCE-DOMAINS sub-TLV........................................10 4.1.3. PCE-DOMAIN sub-TLV.........................................10
4.1.3.1. Area ID DOMAIN sub-TLV...................................10 4.1.4. NEIG-PCE-DOMAIN sub-TLV....................................11
4.1.3.2. AS Number DOMAIN sub-TLV.................................11
4.1.4. PCE-NEIG-DOMAINS sub-TLV...................................11
4.1.5. PCE-CAP-FLAGS sub-TLV......................................11 4.1.5. PCE-CAP-FLAGS sub-TLV......................................11
4.1.6. The CONGESTION sub-TLV.....................................12 4.1.6. The CONGESTION sub-TLV.....................................12
5. Elements of Procedure......................................13 5. Elements of Procedure......................................13
5.1.1. CONGESTION sub-TLV specific procedures.....................14 5.1.1. CONGESTION sub-TLV specific procedures.....................14
6. Backward compatibility.....................................15 6. Backward compatibility.....................................15
7. IANA considerations........................................15 7. IANA considerations........................................15
7.1. IS-IS sub-TLV..............................................15 7.1. IS-IS sub-TLV..............................................15
7.2. PCED sub-TLVs registry.....................................15 7.2. PCED sub-TLVs registry.....................................15
7.3. PCE Capability Flags registry..............................16 7.3. PCE Capability Flags registry..............................16
8. Security Considerations....................................16 8. Security Considerations....................................16
9. Manageability Considerations...............................17 9. Manageability Considerations...............................17
9.1. Control of Policy and Functions............................17 9.1. Control of Policy and Functions............................17
9.2. Information and Data Model.................................17 9.2. Information and Data Model.................................17
9.3. Liveness Detection and Monitoring..........................17 9.3. Liveness Detection and Monitoring..........................17
9.4. Verify Correct Operations..................................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...............................................17
9.6. Impact on network operations...............................18 9.6. Impact on network operations...............................17
10. Acknowledgments............................................18 10. Acknowledgments............................................18
11. References.................................................18 11. References.................................................18
11.1. Normative references.......................................18 11.1. Normative references.......................................18
11.2. Informative references.....................................19 11.2. Informative references.....................................19
12. Editors' Addresses:........................................19 12. Editors' Addresses:........................................19
13. Contributors' Adresses:....................................19 13. Contributors' Adresses:....................................19
14. Intellectual Property Statement............................20 14. Intellectual Property Statement............................20
1. Terminology 1. Terminology
Terminology used in this document Terminology used in this document
ABR: IGP Area Border Router (L1L2 router).
AS: Autonomous System. AS: Autonomous System.
Domain: any collection of network elements within a common sphere
of address management or path computational responsibility.
Examples of domains include IGP areas and Autonomous Systems.
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 (IS-IS). to Intermediate system (IS-IS).
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 IGP area
boundaries. boundaries.
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 AS boundaries.
Inter-area TE LSP: A TE LSP whose path transits two or Inter-area TE LSP: A TE LSP whose path transits two or
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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
network elements within a common sphere of address management or
path computational responsibility (referred to as "domain" in
[RFC4655]). Examples of PCE-Domains include IGP areas and
Autonomous Systems. This should be distinguished from an IS-IS
routing domain as defined by [ISO].
PCEP: Path Computation Element communication Protocol. PCEP: Path Computation Element communication 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 Path [RFC4655] describes the motivations and architecture for a Path
Computation Element (PCE)-based path computation model for Multi Computation Element (PCE)-based path computation model for Multi
Protocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Protocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic
Engineered Label Switched Paths (TE-LSPs). The model allows for the Engineered Label Switched Paths (TE-LSPs). The model allows for the
separation of the PCE from a PCC (also referred to as a non co- separation of the PCE from a Path Computation Client (PCC) (also
located PCE) and allows for cooperation between PCEs. This relies on referred to as a non co-located PCE) and allows for cooperation
a communication protocol between PCC and PCE, and between PCEs. The between PCEs. This relies on a communication protocol between PCC and
requirements for such a communication protocol can be found in PCE, and between PCEs. The requirements for such a communication
[RFC4657] and the communication protocol is defined in [PCEP]. 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 some PCEs in
other domains, e.g. in case of inter-domain TE LSP computation. other domains, e.g. in 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 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, which
allows PCCs to automatically discover a set of PCEs, along with allows PCCs to automatically discover a set of PCEs, along with
additional information about each PCE that may be required for the additional information about each PCE that may be required for the
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discovery requirements set forth in [RFC4674]. This document also discovery requirements set forth in [RFC4674]. This document also
defines extensions allowing a PCE in an IS-IS routing domain to defines extensions allowing a PCE in an IS-IS routing domain to
advertise its processing congestion state. advertise its processing congestion state.
Generic capability advertisement mechanisms for IS-IS are defined in Generic capability advertisement mechanisms for IS-IS are defined in
[IS-IS-CAP]. These allow a router to advertise its capabilities [IS-IS-CAP]. These allow a router to advertise its capabilities
within an IS-IS area or an entire IS-IS routing domain. This document within an IS-IS area or an entire IS-IS 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 aforementioned dynamic PCE discovery requirements.
This document defines a new sub-TLV (named the PCE Discovery (PCED) This document defines a new sub-TLV (named PCE Discovery (PCED) to be
to be carried within the IS-IS Router Capability TLV ([IS-IS-CAP]). carried within the IS-IS Router Capability TLV ([IS-IS-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 section 4 and 5.
This document does not define any new IS-IS elements of procedure. This document does not define any new IS-IS elements of procedure.
The procedures defined in [IS-IS-CAP] should be used. The procedures defined in [IS-IS-CAP] MUST be used.
The IS-IS extensions defined in this document allow for PCE discovery The IS-IS extensions defined in this document allow for PCE discovery
within an IS-IS Routing domain. Solutions for PCE discovery across AS within an IS-IS 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.
This document defines a set of sub-TLVs that are nested within each This document defines a set of sub-TLVs that are nested within each
other. When the degree of nesting TLVs is 2 (a TLV is carried within other. When the degree of nesting TLVs is 2 (a TLV is carried within
another TLV) the TLV carried within a TLV is called a sub-TLV. another TLV) the TLV carried within a TLV is called a sub-TLV.
Strictly speaking, when the degree of nesting is 3, a subsub-TLV is Strictly speaking, when the degree of nesting is 3, a subsub-TLV is
carried within a sub-TLV that is itself carried within a TLV. For the carried within a sub-TLV that is itself carried within a TLV. For the
sake of terminology simplicity, we refer to sub-TLV, a TLV carried sake of terminology simplicity, we refer to sub-TLV, a TLV carried
within a TLV regardless of the degree of nesting. within a TLV regardless of the degree of nesting.
3. Overview 3. Overview
3.1. PCE Information 3.1. PCE Information
The PCE information advertised via IS-IS falls into two categories: The PCE information advertised via IS-IS falls into two categories:
PCE Discovery information and PCE Status information. PCE Discovery information and PCE Congestion information.
3.1.1. PCE Discovery Information 3.1.1. PCE Discovery Information
The PCE Discovery information is comprised of: The PCE Discovery information is comprised 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;
- The PCE inter-domain functions: PCE path computation scope (i.e. - The PCE path computation scope (i.e. inter-area, inter-AS, inter-
inter-area, inter-AS, inter-layer…); layer);
- The PCE domain(s): set of one or more domain(s) into which the PCE - The set of one or more PCE-Domain(s) into which the PCE has
has visibility and can compute paths; visibility and can compute paths;
- The PCE neighbor domain(s): set of one or more neighbor domain(s) - The set of one or more neighbor PCE-Domain(s) towards which a PCE
towards which a PCE can compute paths; can compute paths;
- A set of communication capabilities (e.g. support for - A set of communication capabilities (e.g. support for request
request prioritization) and path computation specific capabilities prioritization) and path computation specific capabilities
(e.g. supported constraints). (e.g. supported constraints).
Optional elements to describe more complex capabilities may also be Optional elements to describe more complex capabilities may also be
advertised. advertised.
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.
3.1.2. PCE Status Information 3.1.2. PCE Congestion Information
The PCE Status is optional and can be used to report a PCE's The PCE Congestion information is optional and can be used to report
processing congestion state along with an estimated congestion a PCE's processing congestion state along with an estimated
duration. This is a dynamic information, which may change with PCE congestion duration. This is dynamic information, which may change
activity. with PCE activity.
Procedures for a PCE to move from a processing congestion state to a Procedures for a PCE to move from a processing congestion state to a
non-congestion state are beyond the scope of this document, but the non-congestion state are beyond the scope of this document, but the
rate at which a PCE Status change is advertised MUST NOT impact by rate at which a PCE Status change is advertised MUST NOT impact by
any means the IGP scalability. Particular attention should be given any means the IGP scalability. Particular attention should be given
on procedures to avoid state oscillations. on procedures to avoid state oscillations.
3.2. Flooding scope 3.2. Flooding scope
The flooding scope for PCE information advertised through IS-IS can The flooding scope for PCE information advertised through IS-IS can
be limited to one or more IS-IS areas the PCE belongs to, or can be be a single L1 area, a L1 area and the L2 sub-domain, or the entire
extended across the entire IS-IS routing domain. IS-IS 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 a
L1L2 router for instance advertising its PCE information within the
L2 area and/or a subset of its attached L1 area(s).
4. IS-IS extensions 4. IS-IS extensions
4.1. The IS-IS PCED TLV 4.1. The IS-IS PCED sub-TLV
The IS-IS PCED TLV is made of a set of non ordered sub-TLVs. The IS-IS PCED sub-TLV is made of a set of non ordered sub-TLVs.
The format of the IS-IS PCED TLV and its sub-TLVs is the identical to The format of the IS-IS PCED sub-TLV and its sub-TLVs is identical to
the TLV format used by the Traffic Engineering Extensions to IS-IS the TLV format used by the Traffic Engineering Extensions to IS-IS
[RFC3784]. That is, the TLV is composed of 1 octet for the type, 1 [RFC3784]. That is, the TLV is composed of 1 octet for the type, 1
octet specifying the TLV length, and a value field. The Length field octet 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 bytes.
The IS-IS PCED TLV has the following format: The IS-IS PCED sub-TLV has the following format:
TYPE: To be assigned by IANA (suggested value = 5) TYPE: To be assigned by IANA (suggested value = 5)
LENGTH: Variable LENGTH: Variable
VALUE: set of sub-TLVs VALUE: set of sub-TLVs
Sub-TLVs types are under IANA control. Sub-TLVs types are under IANA control.
Currently six sub-TLVs are defined (suggested type values to be Currently six sub-TLVs are defined (suggested type values to be
assigned by IANA): assigned by IANA):
Sub-TLV type Length Name Sub-TLV type Length Name
1 variable PCE-ADDRESS sub-TLV 1 variable PCE-ADDRESS sub-TLV
2 3 PATH-SCOPE sub-TLV 2 3 PATH-SCOPE sub-TLV
3 variable PCE-DOMAINS sub-TLV 3 variable PCE-DOMAIN sub-TLV
4 variable PCE-NEIG-DOMAINS sub-TLV 4 variable NEIG-PCE-DOMAIN sub-TLV
5 variable PCE-CA-FLAGS sub-TLV 5 variable PCE-CAP-FLAGS sub-TLV
6 1 CONGESTION sub-TLV 6 1 CONGESTION 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 sub-TLV.
The PCE-DOMAINS and PCE-NEIG-DOMAINS sub-TLVs are optional. They may The PCE-DOMAIN and NEIG-PCE-DOMAIN sub-TLVs are optional. They
be present in the PCED TLV to facilitate selection of inter-domain MAY be present in the PCED sub-TLV to facilitate selection of inter-
PCEs. domain PCEs.
The PCE-CAP-FLAGS sub-TLVs are optional and MAY be present in the The PCE-CAP-FLAGS sub-TLV is optional and MAY be present in the PCED
PCED TLV to facilitate the PCE selection process. sub-TLV to facilitate the PCE selection process.
The CONGESTION sub-TLV is optional and MAY be present in the PCED The CONGESTION sub-TLV is optional and MAY be present in the PCED
TLV, to indicate a PCE's processing congestion state. sub-TLV, to indicate a PCE's processing congestion state.
Any non recognized sub-TLV MUST be silently ignored. Any non recognized sub-TLV MUST be silently ignored.
Additional sub-TLVs could be added in the future to advertise Additional sub-TLVs could be added in the future to advertise
additional PCE information. additional PCE information.
The PCED TLV is carried within an IS-IS CAPABILITY TLV defined in The PCED sub-TLV is carried within an IS-IS CAPABILITY TLV defined in
[IS-IS-CAP]. [IS-IS-CAP].
The following sub-sections describe the sub-TLVs which may be carried
within the PCED sub-TLV.
4.1.1. PCE-ADDRESS sub-TLV 4.1.1. PCE-ADDRESS sub-TLV
The PCE-ADDRESS sub-TLV specifies the IP address that can be The PCE-ADDRESS sub-TLV specifies the 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 the PCE is alive. that is always reachable, provided the PCE is alive.
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 PCED sub-TLV. It MAY appear twice, when the PCE has both an IPv4 and
IPv6 address. It MUST NOT appear more than once for the same address IPv6 address. It MUST NOT appear more than once for the same address
type. type.
The PCE-ADDRESS sub-TLV has the following format: The PCE-ADDRESS sub-TLV has the following format:
TYPE: To be assigned by IANA (Suggested value =1) TYPE: To be assigned by IANA (Suggested value =1)
LENGTH: 5 for IPv4 address and 17 for IPv6 address LENGTH: 5 for IPv4 address and 17 for IPv6 address
VALUE: This comprises one octet indicating the address-type and 4 VALUE: This comprises one octet indicating the address-type and 4
or 16 octets encoding the IPv4 or IPv6 address to be used or 16 bytes encoding the IPv4 or IPv6 address to be used
to reach the PCE to reach the PCE.
Address-type: Address-type:
1 IPv4 1 IPv4
2 IPv6 2 IPv6
4.1.2. The PATH-SCOPE sub-TLV 4.1.2. The 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 intra-area, inter-area, inter-AS, or inter-layer_TE
LSP(s). LSP(s).
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 sub-TLV. There MUST be exactly one instance of the PATH-SCOPE
TLV within each PCED TLV. sub-TLV within each PCED sub-TLV.
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:
TYPE: To be assigned by IANA (Suggested value =2) TYPE: To be assigned by IANA (Suggested value =2)
LENGTH: 3 LENGTH: 3
VALUE: This comprises a one-byte flags field where flag VALUE: This comprises a one-byte flags field where flag
represents a supported path scope, followed by a 2-bytes represents a supported path scope, followed by a 2-bytes
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Pref-L field: PCE's preference for intra-area TE LSPs computation. Pref-L field: PCE's preference for intra-area TE LSPs computation.
Pref-R field: PCE's preference for inter-area TE LSPs computation. Pref-R field: PCE's preference for inter-area TE LSPs computation.
Pref-S field: PCE's preference for inter-AS TE LSPs computation. Pref-S field: PCE's preference for inter-AS TE LSPs computation.
Pref-Y field: PCE's preference for inter-layer TE LSPs computation. Pref-Y field: PCE's preference for inter-layer TE LSPs computation.
Res: Reserved for future usage. Res: Reserved for future usage.
The bits L, R, S, and Y bits are set when the PCE can act as a PCE The L, R, S, and Y bits are set when the PCE can act as a PCE for
for intra-area, inter-area, inter-AS or inter-layer TE LSPs intra-area, inter-area, inter-AS or inter-layer TE LSPs computation
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 LSP computation (that is the PCE can compute a path for inter-area TE LSP computation (that is the PCE can compute a path
towards any neighbor area). Similarly, when set, the Sd bit indicates towards 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 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). (the PCE can compute a path towards any neighbor AS).
When the Rd bit is set, the PCE-NEIG-DOMAIN TLV (see 5.1.4) MUST NOT When the Rd and Sd bit are set, the PCED sub-TLV MUST NOT contain any
contain any Area ID DOMAIN sub-TLVs. NEIG-PCE-DOMAIN sub-TLV (see 4.1.4).
Similarly, when the Sd bit is set, the PCE-NEIG-DOMAIN TLV MUST NOT
contain any AS-DOMAIN sub-TLVs.
When the R/S bit is cleared, the RD/Sd bit SHOULD be cleared and MUST When the R/S bit is cleared, the Rd/Sd bit SHOULD be cleared and MUST
be ignored. be ignored.
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 and
allow the PCE to specify a preference for each computation scope, 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 preference can be used
for weighted load balancing of requests. An operator may decide to for weighted load balancing of requests. An operator may decide to
configure a preference for each computation scope to each PCE so as configure a preference for each computation scope to each PCE so as
to balance the path computation load among them. The algorithms used to balance the path computation load among them. The algorithms used
by a PCC to balance its path computation requests according to such by a PCC to balance its path computation requests according to such
PCE preference are out of the scope of this document and is a matter PCE preference are out of the scope of this document and is a matter
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preferably for inter-AS computation may configure a PrefS higher than preferably for inter-AS computation may configure a PrefS higher than
the PrefR. the PrefR.
When the L bit, R bit, S bit or Y bit are cleared the PrefL, PrefR, When the L bit, R bit, S bit or Y bit are cleared the PrefL, PrefR,
PrefS, PrefY fields SHOULD respectively be set to 0 and MUST be PrefS, PrefY fields SHOULD respectively be set to 0 and MUST be
ignored. ignored.
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.
4.1.3. PCE-DOMAINS sub-TLV 4.1.3. PCE-DOMAIN sub-TLV
The PCE-DOMAINS sub-TLV specifies the set of domains (areas and/or The PCE-DOMAIN sub-TLV specifies a PCE-Domain (areas and/or ASes)
ASes) where the PCE has topology visibility and through which the PCE where the PCE has topology visibility and through which the PCE can
can compute paths. It contains a set of one or more sub-TLVs where compute paths.
each sub-TLV identifies a domain.
The PCE-DOMAINS sub-TLV MAY be present when PCE domains cannot be The PCE-DOMAIN sub-TLV MAY be present when PCE-Domains cannot be
inferred by other IGP information, for instance when the PCE is 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 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 flooding scope is the entire routing domain (see section 5 for a
discussion of how the flooding scope is set and interpreted). discussion of how the flooding scope is set and interpreted).
The PCE-DOMAINS sub-TLV has the following format: A PCED sub-TLV MAY include multiple PCE-DOMAIN sub-TLVs when the PCE
has visibility in multiple PCE-Domains.
The PCE-DOMAIN sub-TLV has the following format:
TYPE: To be assigned by IANA (Suggested value =3) TYPE: To be assigned by IANA (Suggested value =3)
LENGTH: Variable LENGTH: Variable
VALUE: This comprises a set of one or more DOMAIN sub-TLVs where VALUE: This comprises one octet indicating the domain-type (area ID
each DOMAIN sub-TLV identifies a domain where the PCE has or AS Number) and a variable length IS-IS area ID or a 32 bits AS
topology visibility and can compute paths. number, identifying a PCE-domain where the PCE has visibility.
Two DOMAIN sub-TLVs are defined
Sub-TLV type Length Name
1 Variable Area ID sub-TLV
2 4 AS number sub-TLV
At least one DOMAIN sub-TLV MUST be present in the PCE-DOMAINS sub-
TLV. Note than when the PCE visibility is an entire AS, the PCE-
DOMAINS sub-TLV MUST include exactly one AS number sub-TLV, and MUST
not contain an area-ID sub-TLV.
4.1.3.1. Area ID DOMAIN sub-TLV Two domain types are defined:
1 Area ID
2 AS Number
The Area ID is the area address as defined in [ISO].
This sub-TLV carries an IS-IS area ID. It has the following format When coded in two bytes (which is the current defined format as the
time of writing this document), the AS Number field MUST have its
left two bytes set to 0.
TYPE: 1 4.1.4. NEIG-PCE-DOMAIN sub-TLV
LENGTH: Variable
VALUE: This comprises a variable length IS-IS area ID. This is the
combination of an Initial Domain Part (IDP) and High Order
part of the Domain Specific part (HO-DSP)
4.1.3.2. AS Number DOMAIN sub-TLV The NEIG-PCE-DOMAIN sub-TLV specifies a neighbour PCE-domain (area,
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
transits this neighbour PCE-domain.
The AS Number sub-TLV carries an AS number. It has the following A PCED sub-TLV MAY include several NEIG-PCE-DOMAIN sub-TLVs when the
format: PCE can compute paths towards several neighbour PCE-domains.
TYPE: 2 The NEIG-PCE-DOMAIN sub-TLV has the same format as the PCE-DOMAIN
LENGTH: 4 sub-TLV:
VALUE: AS number identifying an AS. When coded in two
bytes (which is the current defined format as the
time of writing this document), the AS Number field
MUST have its left two bytes set to 0.
4.1.4. PCE-NEIG-DOMAINS sub-TLV TYPE: To be assigned by IANA (Suggested value =4)
LENGTH: Variable
VALUE: This comprises one octet indicating the domain-type (area ID
or AS Number) and a variable length IS-IS area ID or a 32 bits AS
number, identifying a PCE-domain towards which the PCE can compute
paths.
The PCE-NEIG-DOMAINS sub-TLV specifies the set of neighbour domains Two domain types are defined:
(areas, ASes) toward which a PCE can compute paths. It means that the 1 Area ID
PCE can compute or take part in the computation of inter-domain TE 2 AS Number
LSPs whose path transits one of these domains. It contains a set of
one or more DOMAIN sub-TLVs where each DOMAIN sub-TLV identifies a
domain.
The PCE-NEIG-DOMAINS sub-TLV has the following format: The Area ID is the area address as defined in [ISO].
TYPE: To be assigned by IANA (Suggested value =4) When coded in two bytes (which is the current defined format as the
LENGTH: Variable time of writing this document), the AS Number field MUST have its
VALUE: This comprises a set of one or more area or/and AS DOMAIN sub- left two bytes set to 0.
TLVs where each sub-TLV identifies a neighbour domain toward
which a PCE can compute path.
The PCE-NEIG-DOMAINS sub-TLV MUST be present if the R bit is set and The NEIG-PCE-DOMAIN sub-TLV MUST be present if the R bit is set and
the Rd bit is cleared, and/or, if the S bit is set and the Sd bit is the Rd bit is cleared, and/or, if the S bit is set and the Sd bit is
cleared. cleared.
The PCE-NEIG-DOMAINS sub-TLV MUST include at least one DOMAIN sub-
TLV. It MUST include at least one Area ID sub-TLV, if the R bit of
the PATH-SCOPE TLV is set and the Rd bit of the PATH-SCOPE TLV is
cleared. Similarly, it MUST include at least one AS number sub-TLV if
the S bit of the PATH-SCOPE TLV is set and the Sd bit of the PATH-
SCOPE TLV is cleared.
4.1.5. PCE-CAP-FLAGS sub-TLV 4.1.5. PCE-CAP-FLAGS sub-TLV
The PCE-CAP-FLAGs sub-TLV is an optional TLV used to indicate PCEP The PCE-CAP-FLAGs sub-TLV is an optional sub-TLV used to indicate
related capabilities. It MAY be present within the PCED TLV. It MUST PCEP related capabilities. It MAY be present within the PCED sub-TLV.
NOT be present more than once. It MUST NOT be present more than once.
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 bit flags numbered from the most significant as bit of units of 32 bit flags numbered from the most significant as bit
zero, where each bit represents one PCE capability. zero, where each bit represents one PCE capability.
The GENERAL-CAP sub-TLV has the following format: The PCE-CAP-FLAGS sub-TLV has the following format:
TYPE: To be assigned by IANA (Suggested value =4) TYPE: To be assigned by IANA (Suggested value =4)
LENGTH: Multiple of 4 LENGTH: Multiple of 4
VALUE: This contains an array of units of 32 bit flags numbered VALUE: This contains an array of units of 32 bit flags numbered
from the most significant as bit zero, where each bit from the most significant as bit zero, where each bit
represents one PCE capability. 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 Capability to handle GMPLS link constraints 0 Path computation with GMPLS link constraints
1 Capability to compute bidirectional paths 1 Bidirectional path computation
2 Capability to compute PSC path 2 Diverse path computation
3 Capability to compute a TDM path 3 Load-balanced path computation
4 Capability to compute a LSC path 4 Synchronized paths computation
5 Capability to compute a FSC path 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
6 Capability to compute link/node/SRLG diverse paths 9-31 Reserved for future assignments by IANA.
7 Capability to compute load-balanced paths
8 Capability to compute a set of paths in a
synchronized Manner
9 Support for multiple objective functions
10 Capability to handle path constraints (e.g. max hop count,
max path metric)
11 Support for Request prioritization.
12 Support for multiple requests within the same
request message.
13-31 Reserved for future assignments by IANA. These capabilities are defined in [RFC4657].
Reserved bits SHOULD be set to zero on transmission and MUST be Reserved bits SHOULD be set to zero on transmission and MUST be
ignored on receipt. ignored on receipt.
4.1.6. The CONGESTION sub-TLV 4.1.6. The CONGESTION sub-TLV
The CONGESTION sub-TLV is used to indicate a PCE's experiences a The CONGESTION sub-TLV is used to indicate that a PCE is experiencing
processing congestion state and may optionally include expected PCE a processing congestion state and may optionally include expected PCE
congestion duration. congestion duration.
The CONGESTION sub-TLV is optional, it MAY be carried within the PCED The CONGESTION sub-TLV is optional, it MAY be carried within the PCED
TLV. It MUST NOT be present more than once. sub-TLV. It MUST NOT be present more than once.
The format of the CONGESTION sub-TLV is as follows: The format of the CONGESTION sub-TLV is as follows:
TYPE: To be assigned by IANA (Suggested value =6) TYPE: To be assigned by IANA (Suggested value =6)
LENGTH: 3 LENGTH: 3
VALUE: This comprises a one-byte bit flags indicating the VALUE: This comprises a one byte of bit flags indicating the
congestion status, followed by a 2-bytes field indicating the congestion status, followed by a 2-bytes field indicating the
congestion duration. congestion duration.
Here is the TLV structure Here is the TLV structure
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| Reserved| Congestion Duration | |C| Reserved| Congestion Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Value Value
skipping to change at page 13, line 35 skipping to change at page 13, line 27
-Congestion Duration: 2-bytes, the estimated PCE congestion -Congestion Duration: 2-bytes, the estimated PCE congestion
duration in seconds. duration in seconds.
When C is set and the Congestion Duration field is equal to 0, this When C is set and the Congestion Duration field is equal to 0, this
means that the Congestion Duration is unknown. means that the Congestion Duration is unknown.
When C is cleared the Congestion Duration SHOULD be set to 0 and MUST When C is cleared the Congestion Duration SHOULD be set to 0 and MUST
be ignored. be ignored.
5. Elements of Procedure 5. Elements of Procedure
The PCED TLV is advertised within an IS-IS Router Capability TLV The PCED sub-TLV is advertised within an IS-IS Router Capability TLV
defined in [IS-IS-CAP]. A such, elements of procedures are inherited defined in [IS-IS-CAP]. As such, elements of procedures are inherited
from those defined in [IS-IS-CAP]. from those defined in [IS-IS-CAP].
The flooding scope is controlled by the S flag in the IS-IS Router The flooding scope is controlled by the S flag in the IS-IS Router
Capability TLV (see [IS-IS-CAP]). When the scope of the PCED TLV is Capability TLV (see [IS-IS-CAP]). When the scope of the PCED sub-TLV
area local it MUST be carried within an IS-IS CAPABILITY TLV having is area local it MUST be carried within an IS-IS Router Capability
the S bit cleared. When the scope of the PCED TLV is the entire IGP TLV having the S bit cleared. When the scope of the PCED sub-TLV is
domain, itMUST be carried within an IS-IS CAPABILITY TLV having the S the entire IS-IS routing domain, it MUST be carried within an IS-IS
bit set. When only the L bit of the PATH-SCOPE sub-TLV is set, the Router Capability TLV having the S bit set. Note that when only the L
flooding scope MUST be local. bit of the PATH-SCOPE sub-TLV is set, the flooding scope MUST be area
local.
A PCE MUST originate a new IS-IS LSP whenever the content Note that a L1L2 node may include both in its L1 and L2 LSPs a PCED
of any of the PCED TLV changes or whenever required by the regular TLV in a Router Capability TLV with the S bit cleared. This allows
IS-IS procedure. restricting the flooding scope to the L1 area and the L2 sub-domain.
When the PCE function is deactivated on a node, the node MUST An IS-IS router MUST originate a new IS-IS LSP whenever there is a
originate a new IS-IS LSP with no longer any PCED TLV. A PCC MUST be change in a PCED TLV associated with a PCE it advertises.
able to detect that the PCED TLV has been removed from an IS-IS LSP.
The PCE address, i.e. the address indicated within the PCE ADDRESS When a PCE is deactivated, the IS-IS Router advertising this PCE MUST
sub-TLV, MUST be distributed as part of IS-IS routing; this allows originate a new IS-IS LSP that does no longer include the
speeding up the detection of a PCE failure. Note that when the PCE corresponding PCED TLV.
address is no longer reachable, this means that the PCE node has
failed or has been torn down, or that there is no longer IP
connectivity to the PCE node.
The PCED TLV is OPTIONAL. When an IS-IS LSP does not contain any PCED The PCE address(s), i.e. the address(s) indicated within the PCE
TLV, this means that the PCE information of that node is unknown. ADDRESS sub-TLV, must be reachable via some prefix(es)
advertised by IS-IS; this allows speeding up the detection of a
PCE failure. Note that when the PCE address is no longer reachable,
this means that the PCE node has failed or has been torn down, or
that there is no longer IP connectivity to the PCE node.
The PCED sub-TLV is OPTIONAL. When an IS-IS LSP does not contain any
PCED TLV, this means that the PCE information of that node is
unknown.
A change in PCED information MUST not trigger any SPF computation at A change in PCED information MUST not trigger any SPF computation at
a receiving router. 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 (e.g., scope of this document. Some information may be configured (e.g.,
address, preferences, scope) and other information may be 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).
5.1.1. CONGESTION sub-TLV specific procedures 5.1. CONGESTION sub-TLV specific procedures
When a PCE enters into a processing congestion state, the conditions When a PCE enters into a processing congestion state, the conditions
of which are implementation dependent, it MAY originate a new IS-IS of which are implementation dependent, a new IS-IS LSP with a
LSP with a CONGESTION sub-TLV with the C bit set and optionally a CONGESTION sub-TLV with the C bit set and optionally a non-null
non-null expected congestion duration. expected congestion duration MAY be generated.
When a PCE exists from the processing congestion state, the When a PCE exists from the processing congestion state, the
conditions of which are implementation dependent, two cases are conditions of which are implementation dependent, two cases are
considered: considered:
- If the congestion duration in the previously originated - If the congestion duration in the previously originated
CONGESTION sub-TLV was null, it SHOULD originate a CONGESTION sub-TLV CONGESTION sub-TLV was null, a CONGESTION sub-TLV with the C bit
with the C bit cleared and a null congestion duration; cleared SHOULD be generated;
- If the congestion duration in the previously originated - If the congestion duration in the previously originated
CONGESTION sub-TLV was non null, it MAY originate a CONGESTION sub- CONGESTION sub-TLV was non null, a CONGESTION sub-TLV with the C bit
TLV with the C bit cleared. Note that in some particular cases it may cleared MAY be generated. Note that in some particular cases it may
be desired to originate a PCES TLV with the C bit cleared if the be desired to originate a CONGESTION sub-TLV with the C bit cleared
congestion duration was over estimated. if the congestion duration was over estimated.
The congestion duration allows a reduction in the amount of IS-IS The congestion duration allows a reduction in the amount of IS-IS
flooding, as only uncongested-to-congested state transitions need flooding, as only uncongested-to-congested state transitions are
advertised. advertised.
A PCE implementation SHOULD support an appropriate dampening An IS-IS implementation SHOULD support an appropriate dampening
algorithm so as to dampen IS-IS flooding in order to not impact the algorithm so as to dampen flooding of PCE Congestion information in
IS-IS scalability. It is RECOMMENDED to introduce some hysteresis for order to not impact the IS-IS scalability. It is RECOMMENDED to
congestion state transition, so as to avoid state oscillations that introduce some hysteresis for congestion state transition, so as to
may impact IS-IS performance. For instance two thresholds MAY be avoid state oscillations that may impact IS-IS performance. For
configured: a resource congestion upper-threshold and a resource instance two thresholds MAY be configured: a resource congestion
congestion lower-threshold. An LSR enters the congested state when upper-threshold and a resource congestion lower-threshold. An LSR
the CPU load reaches the upper threshold and leaves the congested enters the congested state when the CPU load reaches the upper
state when the CPU load goes under the lower threshold. threshold and leaves the congested state when the CPU load goes under
the lower threshold.
Upon receipt of an updated CONGESTION sub-TLV a PCC should take Upon receipt of an updated CONGESTION sub-TLV a PCC should take
appropriate actions. In particular, the PCC SHOULD stop sending appropriate actions. In particular, the PCC SHOULD stop sending
requests to a congested PCE, and SHOULD gradually start sending again requests to a congested PCE, and SHOULD gradually start sending again
requests to a PCE that is no longer congested requests to a PCE that is no longer congested.
6. Backward compatibility 6. Backward compatibility
The PCED TLV defined in this document does not introduce any The PCED sub-TLV defined in this document does not introduce any
interoperability issues. interoperability issues.
An IS-IS router not supporting the PCED TLV will just silently ignore An IS-IS router not supporting the PCED sub-TLV will just silently
the TLV as specified in [IS-IS-CAP]. ignore the TLV as specified in [IS-IS-CAP].
7. IANA considerations 7. IANA considerations
7.1. IS-IS sub-TLV 7.1. IS-IS sub-TLV
Once a registry for the IS-IS Router Capability TLV defined in Once a registry for the IS-IS Router Capability TLV defined in
[IS-IS-CAP] will have been assigned, IANA will assign a new [IS-IS-CAP] has been assigned, IANA will assign a new TLV code-point
TLV code-point for the PCED TLV carried within the Router Capability for the PCED sub-TLV carried within the Router Capability TLV.
TLV.
Value Sub-TLV References Value Sub-TLV References
----- -------- ---------- ----- -------- ----------
5 PCED TLV (this document) 5 PCED sub-TLV (this document)
7.2. PCED sub-TLVs registry 7.2. PCED sub-TLVs registry
The PCED TLV referenced above is constructed from sub-TLVs. Each sub- The PCED sub-TLV referenced above is constructed from sub-TLVs. Each
TLV includes a 8-bit type identifier. sub-TLV includes a 8-bit type identifier.
The IANA is requested to create a new registry and manage TLV type The IANA is requested to create a new registry and manage sub-TLV
identifiers as follows: type identifiers as follows:
- TLV Type - sub-TLV Type
- TLV Name - sub-TLV Name
- Reference - Reference
This document defines five TLVs as follows (suggested values): This document defines five sub-TLVs as follows (suggested values):
Value TLV name References Value TLV name References
----- -------- ---------- ----- -------- ----------
1 PCE-ADDRESS This document 1 PCE-ADDRESS This document
2 PATH-SCOPE This document 2 PATH-SCOPE This document
3 PCE-DOMAINS This document 3 PCE-DOMAIN This document
4 PCE-NEIG-DOMAINS This document 4 NEIG-PCE-DOMAIN This document
5 PCE-CAP-FLAGS This document 5 PCE-CAP-FLAGS This document
6 CONGESTION This document 6 CONGESTION This document
New TLV type values may be allocated only by an IETF Consensus New sub-TLV type values may be allocated only by an IETF Consensus
action. action.
7.3. PCE Capability Flags registry 7.3. 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.
The IANA is requested to create a new registry and to manage the The IANA is requested to create a new registry and to manage the
space of PCE capability bit flags numbering them in the usual IETF space of PCE capability bit flags numbering them in the usual IETF
notation starting at zero, and continuing at least through 31, with notation starting at zero, and continuing at least through 31, with
skipping to change at page 16, line 31 skipping to change at page 16, line 31
- Bit number - Bit number
- Defining RFC - Defining RFC
- Capability Description - Capability Description
Several bits are defined in this document. Here are the suggested Several bits are defined in this document. Here are the suggested
values: values:
Bit Capability Description Bit Capability Description
0 GMPLS link constraints 0 Path computation with GMPLS link constraints
1 Bidirectional paths 1 Bidirectional path computation
2 PSC paths 2 Diverse path computation
3 TDM paths 3 Load-balanced path computation
4 LSC paths 4 Synchronized paths computation
5 FSC paths 5 Support for multiple objective functions
6 Diverse paths 6 Support for additive path constraints
7 Load-balanced paths (max hop count, etc.)
8 Synchronized computation 7 Support for request prioritization
9 Multiple objective functions 8 Support for multiple requests per message
10 Additive path constraints (e.g. max hop count)
11 Request prioritization
12 Multiple requests per message
8. Security Considerations 8. Security Considerations
This document defines IS-IS extensions for PCE discovery within an This document defines IS-IS extensions for PCE discovery within an
administrative domain. Hence the security of the PCE discovery relies administrative domain. Hence the security of the PCE discovery relies
on the security of IS-IS. on the security of IS-IS.
Mechanisms defined to ensure authenticity and integrity of IS-IS LSPs Mechanisms defined to ensure authenticity and integrity of IS-IS LSPs
[RFC3567], and their TLVs, can be used to secure the PCED TLV as well. [RFC3567], and their TLVs, can be used to secure the PCED sub-TLV as
well.
IS-IS provides no mechanism for protecting the privacy of LSAs, and IS-IS provides no mechanism for protecting the privacy of LSPs, and
in particular the privacy PCE discovery information. 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 on the configuration of PCE discovery parameters on PCCs
and PCEs are discussed in section 4.10.1 of [RFC4674]. and PCEs are discussed in section 4.10.1 of [RFC4674].
Particularly, a PCE implementation SHOULD allow configuring the Particularly, a PCE implementation SHOULD allow configuring the
following parameters on the PCE: following parameters on the PCE:
-The PCE IPv4/IPv6 address(es) (see section 4.1.1) -The PCE IPv4/IPv6 address(es) (see section 4.1.1)
-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 4.1.2)
-The PCE domains (see section 4.1.3) -The PCE domains (see section 4.1.3)
-The PCE neighbour domains (see section 4.1.4) -The neighbour PCE domains (see section 4.1.4)
-The PCE capabilities (see section 4.1.5) -The PCE capabilities (see section 4.1.5)
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 IS-IS liveness
detection. IS-IS already includes a liveness detection mechanism detection. IS-IS already includes a liveness detection mechanism
(Hello PDUs), and PCE discovery does not require additional (Hello PDUs), and PCE discovery does not require additional
capabilities. capabilities.
Procedures defined in section 5 allow a PCC detecting when a PCE has Procedures defined in section 5.1 allow a PCC detecting when a PCE
been deactivated, or is no longer reachable. has 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 PCED information in the PCC
and in the PCE, which is stored in the PCED MIB [PCED-MIB]. The and in the PCE, which is stored in the PCED MIB [PCED-MIB]. The
number of dropped, corrupt, and rejected information elements are number of dropped, corrupt, and rejected information elements are
stored in the PCED MIB. stored in the PCED MIB.
9.5. Requirements on Other Protocols and Functional Components 9.5. Requirements on Other Protocols and Functional Components
The IS-IS extensions defined in this documents does not imply any The IS-IS extensions defined in this documents 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 Frequent changes in PCE information, and particularly in PCE
congestion information, may have a significant impact on IS-IS and congestion information, may have a significant impact on IS-IS and
might destabilize the operation of the network by causing the PCCs to might destabilize the operation of the network by causing the PCCs to
swap between PCEs. swap between PCEs.
As discussed in section 5, a PCE implementation SHOULD support an As discussed in section 5.1, a PCE implementation SHOULD support an
appropriate dampening algorithm so as to dampen IS-IS flooding in appropriate dampening algorithm so as to dampen IS-IS flooding in
order to not impact the IS-IS scalability. order to not impact the IS-IS scalability.
Also, as discussed in section 4.10.4 of [RFC4674], it MUST be Also, as discussed in section 4.10.4 of [RFC4674], it MUST be
possible to apply at least the following controls: possible to 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 discovery messages
rate-limiting. rate-limiting.
- 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 and Adrian Farrel for their useful We would like to thank Lucy Wong, Adrian Farrel, Les Ginsberg, Mike
comments and suggestions. Shand and Lou Berger for their useful comments and suggestions.
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.
[ISO] "Intermediate System to Intermediate System Intra-Domain
Routeing Exchange Protocol for use in Conjunction with the
Protocol for Providing the Connectionless-mode Network Service
(ISO 8473)", ISO DP 10589, February 1990.
[RFC3784] Li, T., Smit, H., "IS-IS extensions for Traffic [RFC3784] Li, T., Smit, H., "IS-IS extensions for Traffic
Engineering", RFC 3784, June 2004. Engineering", RFC 3784, June 2004.
[IS-IS-CAP] Vasseur, J.P. et al., "IS-IS extensions for advertising [IS-IS-CAP] Vasseur, J.P. et al., "IS-IS extensions for advertising
router information", draft-ietf-isis-caps, work in progress. router information", draft-ietf-isis-caps, work in progress.
[RFC4655] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation [RFC4655] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation
Element (PCE)-based Architecture", RFC4655, august 2006. Element (PCE)-based Architecture", RFC4655, august 2006.
[RFC4674] Le Roux, J.L., et al. "Requirements for PCE discovery", [RFC4674] Le Roux, J.L., et al. "Requirements for PCE discovery",
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