< draft-ietf-pce-disco-proto-isis-01.txt   draft-ietf-pce-disco-proto-isis-02.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: June 2007 J.P. Vasseur (Editor) Expires: August 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
December 2006 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-01.txt draft-ietf-pce-disco-proto-isis-02.txt
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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 Element(s) (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 of information that can be used for PCE selection.
When the PCE is a Label Switch Router (LSR) participating to the IGP, When the PCE is a Label Switching Router (LSR) participating in the
or even a server participating passively to the IGP, a simple and Interior Gateway Protocol (IGP), or even a server participating
efficient way for PCE discovery consists of relying on IGP flooding. passively in the IGP, a simple and efficient way to discover PCEs
For that purpose this document defines IS-IS extensions for the consists of using IGP flooding. For that purpose this document
advertisement of PCE Discovery information within an IS-IS area or defines extensions to the Intermediate System to Intermediate System
within the entire IS-IS routing domain. (IS-IS) routing protocol for the advertisement of PCE Discovery
information within an IS-IS area or within the entire IS-IS 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 RFC-2119. document are to be interpreted as described in RFC-2119.
Table of Contents Table of Contents
1. Note (to be removed before publication).....................3 1. Terminology.................................................3
2. Terminology.................................................3 2. Introduction................................................4
3. Introduction................................................4 3. Overview....................................................5
4. Overview....................................................5 3.1. PCE Information.............................................5
4.1. PCE Information.............................................5 3.1.1. PCE Discovery Information...................................5
4.1.1. PCE Discovery Information...................................5 3.1.2. PCE Status Information......................................6
4.1.2. PCE Status Information......................................6 3.2. Flooding scope..............................................6
4.2. Flooding scope..............................................6 4. IS-IS extensions............................................6
5. IS-IS extensions............................................6 4.1. The IS-IS PCED TLV..........................................6
5.1. IS-IS PCED TLV format.......................................6 4.1.1. PCE-ADDRESS sub-TLV.........................................7
5.1.1. PCE-ADDRESS sub-TLV.........................................7 4.1.2. The PATH-SCOPE sub-TLV......................................8
5.1.2. The PATH-SCOPE sub-TLV......................................8 4.1.3. PCE-DOMAINS sub-TLV........................................10
5.1.3. PCE-DOMAINS sub-TLV........................................10 4.1.3.1. Area ID DOMAIN sub-TLV...................................10
5.1.3.1. Area ID DOMAIN sub-TLV...................................10 4.1.3.2. AS Number DOMAIN sub-TLV.................................11
5.1.3.2. AS Number DOMAIN sub-TLV.................................10 4.1.4. PCE-NEIG-DOMAINS sub-TLV...................................11
5.1.4. PCE-DEST-DOMAINS sub-TLV...................................11 4.1.5. PCE-CAP-FLAGS sub-TLV......................................11
5.1.5. GENERAL-CAP sub-TLV........................................11 4.1.6. The CONGESTION sub-TLV.....................................12
5.1.6. The PATH-COMP-CAP sub-TLV..................................12 5. Elements of Procedure......................................13
5.1.6.1. Objective Functions sub-TLV..............................13 5.1.1. CONGESTION sub-TLV specific procedures.....................14
5.1.6.2. Opaque Objective Function sub-TLV........................14 6. Backward compatibility.....................................15
5.1.6.3. Switch Caps sub-TLV......................................14 7. IANA considerations........................................15
5.2. The IS-IS PCES sub-TLV.....................................15 7.1. IS-IS sub-TLV..............................................15
5.2.1. The CONGESTION sub-TLV.....................................15 7.2. PCED sub-TLVs registry.....................................15
6. Elements of Procedure......................................16 7.3. PCE Capability Flags registry..............................16
6.1.1. PCES TLV specific procedure................................17 8. Security Considerations....................................16
7. Backward compatibility.....................................17 9. Manageability Considerations...............................17
8. IANA considerations........................................18 9.1. Control of Policy and Functions............................17
8.1. IS-IS sub-TLVs.............................................18 9.2. Information and Data Model.................................17
8.2. Capability bits............................................19 9.3. Liveness Detection and Monitoring..........................17
9. Security Considerations....................................19 9.4. Verify Correct Operations..................................17
10. Manageability Considerations...............................20 9.5. Requirements on Other Protocols and Functional
11. Acknowledgments............................................20 Components...............................................17
12. References.................................................20 9.6. Impact on network operations...............................18
12.1. Normative references.......................................20 10. Acknowledgments............................................18
12.2. Informative references.....................................21 11. References.................................................18
13. Editors' Addresses:........................................21 11.1. Normative references.......................................18
14. Contributors' Adresses:....................................21 11.2. Informative references.....................................19
15. Intellectual Property Statement............................21 12. Editors' Addresses:........................................19
13. Contributors' Adresses:....................................19
1. Note (to be removed before publication) 14. Intellectual Property Statement............................20
This document specifies sub-TLVs to be carried within the IS-IS
Router Capability TLV ([IS-IS-CAP]). Because this document does not
introduce any new IS-IS element of procedure it will be discussed
within the PCE Working Group with a review of the IS-IS Working
Group.
2. Terminology 1. Terminology
Terminology used in this document Terminology used in this document
ABR: IGP Area Border Router (L1L2 router). ABR: IGP Area Border Router (L1L2 router).
AS: Autonomous System. AS: Autonomous System.
Domain: any collection of network elements within a common sphere Domain: any collection of network elements within a common sphere
of address management or path computational responsibility. of address management or path computational responsibility.
Examples of domains include IGP areas and Autonomous Systems. Examples of domains include IGP areas and Autonomous Systems.
IGP: Interior Gateway Protocol. Either of the two routing
protocols Open Shortest Path First (OSPF) or Intermediate System
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 through two or Inter-area TE LSP: A TE LSP whose path transits two or
more IGP areas. more IGP areas. That is a TE-LSP that crosses at least one IGP
area boundary.
Inter-AS TE LSP: A TE LSP whose path transits through two or more Inter-AS TE LSP: A TE LSP whose path transits two or more
ASes or sub-ASes (BGP confederations). ASes or sub-ASes (BGP confederations). That is a TE-LSP that
crosses at least one AS boundary.
LSR: Label Switch Router. IS-IS LSP: Link State PDU
PCC: Path Computation Client: any client application requesting a LSR: Label Switching Router.
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.
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.
3. 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 PCE from PCC (also referred to as non co-located PCE) separation of the PCE from a PCC (also referred to as a non co-
and allows for cooperation between PCEs. This relies on a located PCE) and allows for cooperation between PCEs. This relies on
communication protocol between PCC and PCE, and between PCEs. The a communication protocol between PCC and PCE, and between PCEs. The
requirements for such communication protocol can be found in [RFC4657] requirements for such a communication protocol can be found in
and the communication protocol is defined in [PCEP]. [RFC4657] and the communication protocol is defined in [PCEP].
The PCE architecture requires, of course, that a PCC be aware of the The PCE architecture requires that a PCC be aware of the location of
location of one or more PCEs in its domain, and also potentially of one or more PCEs in its domain, and also potentially of some PCEs in
some PCEs in other domains, e.g. in case of inter-domain TE LSP other domains, e.g. in case of inter-domain TE LSP computation.
computation.
A network may comprise a large number of PCEs with potentially A network may contain a large number of PCEs with potentially
distinct capabilities. In such context it is highly desirable to have distinct capabilities. In such a context it is highly desirable to
a mechanism for automatic and dynamic PCE discovery, which allows have a mechanism for automatic and dynamic PCE discovery, which
PCCs to automatically discover a set of PCEs, along with additional allows PCCs to automatically discover a set of PCEs, along with
information required for PCE selection, and to dynamically detect new additional information about each PCE that may be required for the
PCEs or any modification of PCE information. Detailed requirements PCC to perform PCE selection. Additionally, it is valuable for a PCC
for such a PCE discovery mechanism are described in [RFC4674]. to dynamically detect new PCEs or any modification of the PCE
information. Detailed requirements for such a PCE discovery mechanism
are provided in [RFC4674].
Moreover, it may also be useful to discover when a PCE experiences Moreover, it may also be useful to discover when a PCE experiences
some processing congestion state and exits such state, in order for processing congestion and when it exits such a state, in order for
the PCCs to take some appropriate actions (e.g. redirect to another the PCCs to take some appropriate actions (e.g. redirect their
PCE). Note that the PCE selection algorithm is out of the scope of requests to another PCE). Note that the PCE selection algorithm
this document. applied by a PCC is out of the scope of this document.
When PCCs are LSRs participating to the IGP (OSPF, IS-IS), and PCEs When PCCs are LSRs participating in the IGP (OSPF, IS-IS), and PCEs
are LSRs or a servers also participating to the IGP, an efficient are either LSRs or servers also participating in the IGP, an
mechanism for PCE discovery within an IGP routing domain consists of effective mechanism for PCE discovery within an IGP routing domain
relying on IGP advertisements. consists of utilizing IGP advertisements.
This document defines IS-IS extensions allowing a PCE participating This document defines IS-IS extensions to allow a PCE in an IS-IS
to the IS-IS routing to advertise its location along with some routing domain to advertise its location along with some information
information useful for PCE selection, so as to satisfy dynamic PCE useful to a PCC for PCE selection, so as to satisfy dynamic PCE
discovery requirements set forth in [RFC4674]. This document also discovery requirements set forth in [RFC4674]. This document also
defines extensions allowing a PCE participating to the IS-IS routing defines extensions allowing a PCE in an IS-IS routing domain to
to advertise its potential processing congestion state. advertise its processing congestion state.
Generic capability mechanisms for IS-IS have been defined in [IS-IS- Generic capability advertisement mechanisms for IS-IS are defined in
CAP] the purpose of which is to allow a router to advertise its [IS-IS-CAP]. These allow a router to advertise its capabilities
capability within an IS-IS area or an entire IS-IS routing domain. within an IS-IS area or an entire IS-IS routing domain. This document
Such IS-IS extensions fully satisfy the aforementioned dynamic PCE leverages this generic capability advertisement mechanism to fully
discovery requirements. satisfy the aforementioned dynamic PCE discovery requirements.
This document defines two new sub-TLVs (named the PCE Discovery This document defines a new sub-TLV (named the PCE Discovery (PCED)
(PCED) TLV and the PCE Status (PCES) TLV) for IS-IS, to be carried to be carried within the IS-IS Router Capability TLV ([IS-IS-CAP]).
within the IS-IS Capability TLV ([IS-IS-CAP]). The PCE information
advertised is detailed in section 4. Protocol extensions and
procedures are defined in section 5 and 6.
This document does not define any new IS-IS element of procedure but The PCE information advertised is detailed in section 3. Protocol
how the procedures defined in [IS-IS-CAP] should be used. extensions and procedures are defined in section 4 and 5.
The routing extensions defined in this document allow for PCE This document does not define any new IS-IS elements of procedure.
discovery within an IS-IS Routing domain. Solutions for PCE discovery The procedures defined in [IS-IS-CAP] should be used.
across AS boundaries are beyond the scope of this document, and for
further study. The IS-IS extensions defined in this document allow for PCE discovery
within an IS-IS Routing domain. Solutions for PCE discovery across AS
boundaries are beyond the scope of this document, and for further
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.
4. Overview 3. Overview
4.1. 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 Status information.
4.1.1. 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 must be - The PCE location: an IPv4 and/or IPv6 address that is used to reach
used to reach the PCE. It is RECOMMENDED to use addresses 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 inter-domain functions: PCE path computation scope (i.e.
inter-area, inter-AS, inter-layer…); inter-area, inter-AS, inter-layer…);
- The PCE domain(s): set of one or more domain(s) where the PCE has - The PCE domain(s): set of one or more domain(s) into which the PCE
visibility and can compute paths; has visibility and can compute paths;
- The PCE Destination domain(s): set of one or more destination - The PCE neighbor domain(s): set of one or more neighbor domain(s)
domain(s) towards which a PCE can compute paths; towards which a PCE can compute paths;
- A set of general PCEP capabilities (e.g. support for request - A set of communication capabilities (e.g. support for
prioritization) and path computation specific capabilities request prioritization) and path computation specific capabilities
(e.g. supported constraints, supported objective functions). (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.
4.1.2. PCE Status Information 3.1.2. PCE Status Information
The PCE Status is optional and can be used to report a PCE processing The PCE Status is optional and can be used to report a PCE's
congested state along with an estimated congestion duration. This is processing congestion state along with an estimated congestion
dynamic information, which may change with PCE activity. duration. This is a dynamic information, which may change with PCE
activity.
Procedures for a PCE to move from a processing congested state to a Procedures for a PCE to move from a processing congestion state to a
non-congested 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 mean the IGP scalability. Particular attention should be given on any means the IGP scalability. Particular attention should be given
procedures to avoid state oscillations. on procedures to avoid state oscillations.
4.2. Flooding scope 3.2. Flooding scope
The flooding scope for PCE Discovery Information can be limited to The flooding scope for PCE information advertised through IS-IS can
one or more IS-IS areas the PCE belongs to or can be extended across be limited to one or more IS-IS areas the PCE belongs to, or can be
the entire IS-IS routing domain. extended across the entire IS-IS 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 of a flooding scope may comprise these areas. This could be the case for a
L1L2 router for instance advertising its PCE information within the L1L2 router for instance advertising its PCE information within the
L2 level and/or a subset of its attached L1 area(s). L2 area and/or a subset of its attached L1 area(s).
5. IS-IS extensions 4. IS-IS extensions
5.1. IS-IS PCED TLV format 4.1. The IS-IS PCED TLV
The IS-IS PCED TLV is made of various non ordered sub-TLVs. The IS-IS PCED 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 same as the The format of the IS-IS PCED TLV and its sub-TLVs is the identical to
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. octet specifying the TLV length, and a value field. The Length field
defines the length of the value portion in octets.
The IS-IS PCED TLV has the following format: The IS-IS PCED TLV has the following format:
TYPE: To be assigned by IANA 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 five 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-DOMAINS sub-TLV
4 variable PCE-DEST-DOMAINS sub-TLV 4 variable PCE-NEIG-DOMAINS sub-TLV
5 variable GENERAL-CAP sub-TLV 5 variable PCE-CA-FLAGS sub-TLV
6 variable PATH-COMP-CAP 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 TLV.
The PCE-DOMAINS and PCE-DEST-DOMAINS sub-TLVs are optional. They may The PCE-DOMAINS and PCE-NEIG-DOMAINS sub-TLVs are optional. They may
be present in the PCED TLV to facilitate selection of inter-domain be present in the PCED TLV to facilitate selection of inter-domain
PCEs. PCEs.
The GENERAL-CAP and PATH-COMP-CAP sub-TLVs are optional and MAY be The PCE-CAP-FLAGS sub-TLVs are optional and MAY be present in the
present in the PCED TLV to facilitate the PCE selection process. PCED TLV to facilitate the PCE selection process.
The CONGESTION sub-TLV is optional and MAY be present in the PCED
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 TLV is carried within an IS-IS CAPABILITY TLV defined in
[IS-IS-CAP], whose S bit is determined by the desired flooding scope. [IS-IS-CAP].
5.1.1. PCE-ADDRESS sub-TLV 4.1.1. PCE-ADDRESS sub-TLV
The PCE-ADDRESS sub-TLV specifies the IP address that MUST 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 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 octets 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
5.1.2. The PATH-SCOPE sub-TLV 4.1.2. The PATH-SCOPE sub-TLV
The PATH-SCOPE sub-TLV indicates the PCE path computation scope which The PATH-SCOPE sub-TLV indicates the PCE path computation scope,
refers to the PCE ability to compute or take part into 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 TLV. There MUST be exactly one instance of the PATH-SCOPE sub-
TLV within each PCED TLV. TLV within each PCED 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 (intra-area, inter-area, inter-AS, inter-layer) supported path scopes, and four fields indicating PCE preferences.
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 flag of bits where each bit 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
preferences field indicating PCE preferences. preferences field indicating PCE preferences.
Here is the structure of the bits flag: Here is the structure of the bits flag:
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|0|1|2|3|4|5|Res| |0|1|2|3|4|5|Res|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Bit Path Scope Bit Path Scope
0 L bit: Can compute intra-area path 0 L bit: Can compute intra-area path
1 R bit: Can act as PCE for inter-area TE LSPs computation 1 R bit: Can act as PCE for inter-area TE LSP computation
2 Rd bit: Can act as a default PCE for inter-area TE LSPs 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 LSPs 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 LSPs 4 Sd bit: Can act as a default PCE for inter-AS TE LSPs
computation computation
5 Y bit: Can compute or take part into the computation of
paths across layers 5 Y bit: Can compute or take part into the computation of
paths across layers
6-7 Reserved for future usage. 6-7 Reserved for future usage.
Here is the structure of the preferences field Here is the structure of the preferences field
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PrefL|PrefR|PrefS|PrefY| Res | |PrefL|PrefR|PrefS|PrefY| Res |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Pref-L field: PCE's preference for intra-area TE LSPs computation. Res: Reserved for future usage.
Pref-R field: PCE’s preference for inter-area TE LSPs computation. Pref-L field: PCE's preference for intra-area TE LSPs computation.
Pref-S field: PCE’s preference for inter-AS TE LSPs computation. Pref-R field: PCE's preference for inter-area TE LSPs computation.
Pref-Y field: PCE's preference for inter-layer TE LSPs computation. Pref-S field: PCE's preference for inter-AS TE LSPs computation.
Res: Reserved for future usage. Pref-Y field: PCE's preference for inter-layer TE LSPs computation.
The bits L, R, S and Y bits are set when the PCE can act as a PCE for Res: Reserved for future usage.
intra-area, inter-area, inter-AS and inter-layer TE LSPs computation
respectively. These bits are non mutually exclusive. The bits L, R, S, and Y bits are set when the PCE can act as a PCE
for intra-area, inter-area, inter-AS or inter-layer TE LSPs
computation respectively. These bits are non-exclusive.
When set the Rd bit indicates that the PCE can act as a default PCE When set the Rd bit indicates that the PCE can act as a default PCE
for inter-area TE LSPs computation (the PCE can compute path for any for inter-area TE LSP computation (that is the PCE can compute a path
destination area). Similarly, when set the Sd bit indicates that the towards any neighbor area). Similarly, when set, the Sd bit indicates
PCE can act as a default PCE for inter-AS TE LSPs computation (the that the PCE can act as a default PCE for inter-AS TE LSP computation
PCE can compute path for any destination AS). (the PCE can compute a path towards any neighbor AS).
When the Rd bit is set, the PCE-DEST-DOMAIN TLV (see 5.1.4) does not When the Rd bit is set, the PCE-NEIG-DOMAIN TLV (see 5.1.4) MUST NOT
contain any Area ID DOMAIN sub-TLV. contain any Area ID DOMAIN sub-TLVs.
Similarly, when the Sd bit is set, the PCE-DEST-DOMAIN TLV does not Similarly, when the Sd bit is set, the PCE-NEIG-DOMAIN TLV MUST NOT
contain any AS-DOMAIN sub-TLV. contain any AS-DOMAIN sub-TLVs.
The PrefL, PrefR, PrefS and PrefY fields are 3-bit long and allow the When the R/S bit is cleared, the RD/Sd bit SHOULD be cleared and MUST
PCE to specify a preference for each computation scope, where 7 be ignored.
reflects the highest preference. Such preference can be used for
weighted load balancing of requests. An operator may decide to The PrefL, PrefR, PrefS and PrefY fields are each three bits long and
configure a preference to each PCE so as to balance the path allow the PCE to specify a preference for each computation scope,
computation load among them, with respect to their respective CPU where 7 reflects the highest preference. Such preference can be used
capacity. The algorithms used by a PCC to balance its path for weighted load balancing of requests. An operator may decide to
computation requests according to such PCE’s preference are out of configure a preference for each computation scope to each PCE so as
the scope of this document. Same or distinct preferences may be used to balance the path computation load among them. The algorithms used
for different scopes. For instance an operator that wants a PCE by a PCC to balance its path computation requests according to such
capable of both inter-area and inter-AS computation to be used PCE preference are out of the scope of this document and is a matter
for local or network wide policy. The same or distinct preferences
may be used for each scopes. For instance an operator that wants a
PCE capable of both inter-area and inter-AS computation to be used
preferably for inter-AS computation may configure a PrefS higher than preferably for inter-AS computation may configure a PrefS higher than
the PrefR. When the PrefL, PrefR, PRefS or PrefY is cleared, this the PrefR.
indicates an absence of preference.
When the L bit, R bit, S 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 MUST respectively be set to 0. PrefS, PrefY fields SHOULD respectively be set to 0 and MUST be
ignored.
5.1.3. PCE-DOMAINS sub-TLV Both reserved fields SHOULD be set to zero on transmission and MUST
be ignored on receipt.
The PCE-DOMAINS sub-TLV specifies the set of domains (areas or AS) 4.1.3. PCE-DOMAINS sub-TLV
where the PCE has topology visibility and can compute paths. It
contains a set of one or more sub-TLVs where each sub-TLV identifies
a domain.
The PCE-DOMAINS sub-TLV MUST be present when PCE domains cannot be The PCE-DOMAINS sub-TLV specifies the set of domains (areas and/or
ASes) where the PCE has topology visibility and through which the PCE
can compute paths. It contains a set of one or more sub-TLVs where
each sub-TLV identifies a domain.
The PCE-DOMAINS 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. flooding scope is the entire routing domain (see section 5 for a
discussion of how the flooding scope is set and interpreted).
The PCE-DOMAINS sub-TLV has the following format: The PCE-DOMAINS sub-TLV has the following format:
TYPE: To be assigned by IANA (Suggested value =2) 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 a set of one or more DOMAIN sub-TLVs where
each DOMAIN sub-TLV identifies a domain where the PCE has each DOMAIN sub-TLV identifies a domain where the PCE has
topology visibility and can compute paths topology visibility and can compute paths.
DOMAIN sub-TLVs types are under IANA control. Two DOMAIN sub-TLVs are defined
Currently two DOMAIN sub-TLVs are defined (suggested type values to Sub-TLV type Length Name
be assigned by IANA): 1 Variable Area ID sub-TLV
Sub-TLV type Length Name 2 4 AS number sub-TLV
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- 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- TLV. Note than when the PCE visibility is an entire AS, the PCE-
DOMAINS sub-TLV MUST uniquely include one AS number sub-TLV. DOMAINS sub-TLV MUST include exactly one AS number sub-TLV, and MUST
not contain an area-ID sub-TLV.
5.1.3.1. Area ID DOMAIN sub-TLV 4.1.3.1. Area ID DOMAIN sub-TLV
This sub-TLV carries an IS-IS area ID. It has the following format This sub-TLV carries an IS-IS area ID. It has the following format
TYPE: To be assigned by IANA (Suggested value =1) TYPE: 1
LENGTH: Variable LENGTH: Variable
VALUE: This comprises a variable length IS-IS area ID. This is the VALUE: This comprises a variable length IS-IS area ID. This is the
combination of an Initial Domain Part (IDP) and High Order combination of an Initial Domain Part (IDP) and High Order
part of the Domain Specific part (HO-DSP) part of the Domain Specific part (HO-DSP)
5.1.3.2. AS Number DOMAIN sub-TLV 4.1.3.2. AS Number DOMAIN sub-TLV
The AS Number sub-TLV carries an AS number. It has the following The AS Number sub-TLV carries an AS number. It has the following
format: format:
TYPE: To be assigned by IANA (Suggested value =2) TYPE: 2
LENGTH: 4 LENGTH: 4
VALUE: AS number identifying an AS. When coded on two VALUE: AS number identifying an AS. When coded in two
bytes (which is the current defined format as the bytes (which is the current defined format as the
time of writing this document), the AS Number field time of writing this document), the AS Number field
MUST have its left two bytes set to 0. MUST have its left two bytes set to 0.
5.1.4. PCE-DEST-DOMAINS sub-TLV 4.1.4. PCE-NEIG-DOMAINS sub-TLV
The PCE-DEST-DOMAINS sub-TLV specifies the set of destination domains The PCE-NEIG-DOMAINS sub-TLV specifies the set of neighbour domains
(areas, AS) toward which a PCE can compute paths. It means that the (areas, ASes) toward which a PCE can compute paths. It means that the
PCE can compute or take part in the computation of inter-domain TE PCE can compute or take part in the computation of inter-domain TE
LSPs whose destinations are located within one of these domains. It LSPs whose path transits one of these domains. It contains a set of
contains a set of one or more DOMAIN sub-TLVs where each DOMAIN sub- one or more DOMAIN sub-TLVs where each DOMAIN sub-TLV identifies a
TLV identifies a domain. domain.
The PCE-DEST-DOMAINS sub-TLV has the following format: The PCE-NEIG-DOMAINS sub-TLV has the following format:
TYPE: To be assigned by IANA (Suggested value =3) TYPE: To be assigned by IANA (Suggested value =4)
LENGTH: Variable LENGTH: Variable
VALUE: This comprises a set of one or more area or/and AS DOMAIN sub- VALUE: This comprises a set of one or more area or/and AS DOMAIN sub-
TLVs where each sub-TLV identifies a destination domain toward TLVs where each sub-TLV identifies a neighbour domain toward
which a PCE can compute path. which a PCE can compute path.
The PCE-DEST-DOMAINS sub-TLV MUST be present if the R bit is set and The PCE-NEIG-DOMAINS 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-DEST-DOMAINS sub-TLV MUST include at least one DOMAIN sub- 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 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 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 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- the S bit of the PATH-SCOPE TLV is set and the Sd bit of the PATH-
SCOPE TLV is cleared. SCOPE TLV is cleared.
5.1.5. GENERAL-CAP sub-TLV 4.1.5. PCE-CAP-FLAGS sub-TLV
The GENERAL-CAP sub-TLV is an optional TLV used to indicate PCEP The PCE-CAP-FLAGs sub-TLV is an optional TLV used to indicate PCEP
related capabilities. It carries a 32-bit flag, where each bit related capabilities. It MAY be present within the PCED TLV. It MUST
corresponds to a general PCE capability. It MAY also include optional NOT be present more than once.
sub-TLVs to encode more complex capabilities.
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
zero, where each bit represents one PCE capability.
The GENERAL-CAP sub-TLV has the following format: The GENERAL-CAP 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: Variable LENGTH: Multiple of 4
VALUE: This comprises a 32-bit General Capabilities flag where VALUE: This contains an array of units of 32 bit flags numbered
each bit corresponds to a general PCE capability, and from the most significant as bit zero, where each bit
optional sub-TLVs that may be defined to specify more represents one PCE capability.
complex capabilities. Currently no sub-TLVs are defined.
The following bits in the General Capabilities 32-bit flag are to be
assigned by IANA:
0 1 2 3 IANA is requested to manage the space of the PCE Capability Flags
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The following bits are to be assigned by IANA:
|P|M| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Bit Capabilities Bit Capabilities
0 P bit: Support for Request prioritization. 0 Capability to handle GMPLS link constraints
1 M bit: Support for multiple requests within the same 1 Capability to compute bidirectional paths
request message. 2 Capability to compute PSC path
3 Capability to compute a TDM path
2-31 Reserved for future assignments by IANA. 4 Capability to compute a LSC path
5 Capability to compute a FSC path
5.1.6. The PATH-COMP-CAP sub-TLV
The PATH-COMP-CAP sub-TLV is an optional TLV used to indicate path
computation specific capabilities of a PCE.
It comprises a 32-bit flag, where each bit corresponds to a path
computation capability. It MAY also include optional sub-TLVs to
encode more complex capabilities.
The PATH-COMP-CAP sub-TLV has the following format:
TYPE: To be assigned by IANA (suggested value = 5)
LENGTH: Variable
VALUE: This comprises one 32 bit Path Computation Capabilities
Flag, where each bit corresponds to a path computation
capability, and optional sub-TLVs that may be defined to
specify more complex capabilities. Three optional sub-TLVs
are currently defined.
The following bits in the Path Computation Capabilities 32-bit Flag
are to be assigned by IANA:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|G|B|D|L|S|0|P| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Bit Capabilities
0 G bit: Capability to handle GMPLS link contraints
1 B bit: Capability to compute bidirectional paths
2 D bit: Capability to compute link/node/SRLG diverse paths
3 L bit: Capability to compute load-balanced paths
4 S bit: Capability to compute a set of paths in a
synchronized Manner
5 O bit: Support for multiple objective functions
6 P bit: Capability to handle path constraints (e.g. max hop
count, metric bound)
7-31 Reserved for future assignments by IANA.
The G, B, D, L, S, O and P bits are not exclusive.
Three optional sub-TLVs are currently defined for the PATH-COMP-CAP
TLV:
- The Objective Functions sub-TLV (type to be defined, suggested
value =1) that carries a list of supported objective functions,
where each objective function is identified by a 16 bit integer.
- The Opaque Objective Function sub-TLV (type to be defined,
suggested value =2) that allows the user to encode a specific
objective function in any appropriate language.
- The Switch Caps sub-TLV (type to be defined, suggested value =3)
that carries a list of supported switching capabilities. This
means that the PCE can compute paths for the listed switching
capabilities.
5.1.6.1. Objective Functions sub-TLV
The format of the Objective Functions sub-TLV is as follows:
TYPE: To be defined by IANA (suggested value =1)
LENGTH: Variable (N*2)
VALUE: This comprises a set of one or more 16 bit function
ids, where each function id identifies a supported
objective functions.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| function 1 | function 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| function N | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Objectives functions and their identification will be defined in a
separate document.
The Objective Functions sub-TLV is optional. It MAY be present within
the PATH-COMP-CAP TLV. When present it MUST be present only once in
the PATH-COMP-CAP TLV.
5.1.6.2. Opaque Objective Function sub-TLV
The format of the Opaque Objective Function sub-TLV is as follows:
TYPE: To be defined by IANA (suggested value =2)
LENGTH: Variable
VALUE: This encodes a specific objective function in any
appropriate language.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque objective function |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Opaque Objective function sub-TLV is optional. The PATH-COMP-CAP TLV
MAY comprise 0, one or more Opaque Objective Functions.
5.1.6.3. Switch Caps sub-TLV
The format of the Switch Caps sub-TLV is as follows:
TYPE To be defined by IANA (suggested value =3)
LENGTH Variable = N, where N is the number of supported
switching capabilities
VALUE This comprises a set of one or more 8-bit switching
types, where each switching types identifies a
supported switching capability.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SC type | SC type | SC type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Switching type values are defined in [RFC4205].
The Switch Caps sub-TLV is optional. It MAY be present in the PATH-COMP-
CAP TLV. When present it MUST be present only once in the PATH-COMP-CAP
TLV.
5.2. The IS-IS PCES sub-TLV
The IS-IS PCE Status TLV (PCES sub-TLV) carries information related
to PCE processing congestion state. The PCES sub-TLV is carried
within an IS-IS Capability TLV which is defined in [IS-IS-CAP].
The IS-IS PCES sub-TLV has the following format:
TYPE: To be assigned by IANA
LENGTH: Variable
VALUE: set of sub-TLVs
Sub-TLVs types are under IANA control.
Currently two sub-TLVs are defined (suggested type values to be
assigned by IANA):
Sub-TLV type Length Name
1 variable PCE-ADDRESS sub-TLV
2 3 CONGESTION sub-TLV
There MUST be exactly one occurrence of the PCE-ADDRESS and 6 Capability to compute link/node/SRLG diverse paths
CONGESTION sub-TLVs within a PCES sub-TLV. The PCE-ADDRESS sub-TLV is 7 Capability to compute load-balanced paths
defined in section 5.1.1. It carries one of the PCE IP addresses and 8 Capability to compute a set of paths in a
is used to identify the PCE experiencing a processing congestion synchronized Manner
state. This is required as the PCES and PCED TLVs may be carried in 9 Support for multiple objective functions
separate IS-IS Capability TLVs. 10 Capability to handle path constraints (e.g. max hop count,
A PCE implementation MUST use the same IP address for the PCE- max path metric)
ADDRESS sub-TLV carried within the PCED sub-TLV and the PCE-ADDRESS 11 Support for Request prioritization.
sub-TLV carried within the PCES sub-TLV. 12 Support for multiple requests within the same
request message.
Any non recognized sub-TLV MUST be silently ignored. 13-31 Reserved for future assignments by IANA.
Additional sub-TLVs could be added in the future to advertise Reserved bits SHOULD be set to zero on transmission and MUST be
additional congestion information. ignored on receipt.
5.2.1. The CONGESTION sub-TLV 4.1.6. The CONGESTION sub-TLV
The CONGESTION sub-TLV is used to indicate whether a PCE experiences The CONGESTION sub-TLV is used to indicate a PCE's experiences a
a processing congestion state or not along with optionally the PCE processing congestion state and may optionally include expected PCE
expected congestion duration. congestion duration.
The CONGESTION sub-TLV is mandatory. There MUST be a single instance The CONGESTION sub-TLV is optional, it MAY be carried within the PCED
of the CONGESTION sub-TLV within the PCES TLV. 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 =2) TYPE: To be assigned by IANA (Suggested value =6)
LENGTH: 3 LENGTH: 3
VALUE: This comprises a one-byte flag of bits indicating the VALUE: This comprises a one-byte 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
-C bit: When set this indicates that the PCE experiences -C bit: When set this indicates that the PCE is experiencing
congestion and cannot accept any new request. When congestion and cannot accept any new request. When
cleared this indicates that the PCE does not cleared this indicates that the PCE is not
experience congestion and can accept new requests. experiencing congestion and can accept new requests.
-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 MUST be set to 0. When C is cleared the Congestion Duration SHOULD be set to 0 and MUST
be ignored.
6. Elements of Procedure 5. Elements of Procedure
The PCED and PCES TLV are carried within an IS-IS Capability TLV The PCED TLV is advertised within an IS-IS Router Capability TLV
defined in [IS-IS-CAP]. defined in [IS-IS-CAP]. A such, elements of procedures are inherited
from those defined in [IS-IS-CAP].
As PCES information is likely to change more frequently than the PCED The flooding scope is controlled by the S flag in the IS-IS Router
information, it is RECOMMENDED to carry PCES and PCED TLVs in Capability TLV (see [IS-IS-CAP]). When the scope of the PCED TLV is
separate IS-IS Capability TLVs, so as not to carry all PCED area local it MUST be carried within an IS-IS CAPABILITY TLV having
information each time the PCE status changes. the S bit cleared. When the scope of the PCED TLV is the entire IGP
domain, itMUST be carried within an IS-IS CAPABILITY TLV having the S
bit set. When only the L bit of the PATH-SCOPE sub-TLV is set, the
flooding scope MUST be local.
An IS-IS router MUST originate a new IS-IS LSP whenever the content A PCE MUST originate a new IS-IS LSP whenever the content
of any of the PCED TLV or PCES TLV changes or whenever required by of any of the PCED TLV changes or whenever required by the regular
the regular IS-IS procedure (LSP refresh). IS-IS procedure.
When the scope of the PCED or PCES TLV is area local it MUST be When the PCE function is deactivated on a node, the node MUST
carried within an IS-IS CAPABILITY TLV having the S bit cleared. originate a new IS-IS LSP with no longer any PCED TLV. A PCC MUST be
When the scope of the PCED or PCES TLV is the entire IGP domain, the able to detect that the PCED TLV has been removed from an IS-IS LSP.
PCED TLV MUST be carried within an IS-IS CAPABILITY TLV having the S
bit set.
When only the L bit of the PATH-SCOPE sub-TLV is set, the flooding
scope MUST be local.
Note that the flooding scopes of the PCED and PCES TLVs may be
distinct, in which case they are carried in distinct IS-IS Capability
TLVs.
The PCED and PCES sub-TLVs are OPTIONAL. When an IS-IS LSP does not The PCE address, i.e. the address indicated within the PCE ADDRESS
contain any PCED or PCES sub-TLV, this means that the PCE information sub-TLV, MUST be distributed as part of IS-IS routing; this allows
of that node is unknown. 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.
A change in PCED or PCES information MUST not trigger any The PCED TLV is OPTIONAL. When an IS-IS LSP does not contain any PCED
SPF computation. TLV, this means that the PCE information of that node is unknown.
The way PCEs retrieve their own information is out of the scope of A change in PCED information MUST not trigger any SPF computation at
this document. Some information may be configured (e.g. address, a receiving router.
preferences, scope) and other information may be automatically
retrieved (e.g. areas of visibility).
6.1.1. PCES TLV specific procedure The way PCEs determine the information they advertise is out of the
scope of this document. Some information may be configured (e.g.,
address, preferences, scope) and other information may be
automatically determined by the PCE (e.g. areas of visibility).
5.1.1. 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 SHOULD originate a new IS- of which are implementation dependent, it MAY originate a new IS-IS
IS LSP with a Capability TLV carrying a PCES TLV with the C bit set LSP with a CONGESTION sub-TLV with the C bit set and optionally a
and optionally a non-null expected congestion duration. non-null expected congestion duration.
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 PCES - If the congestion duration in the previously originated
TLV was null, it SHOULD originate a PCES TLV with the C bit cleared CONGESTION sub-TLV was null, it SHOULD originate a CONGESTION sub-TLV
and a null congestion duration; with the C bit cleared and a null congestion duration;
- If the congestion duration in the previously originated PCES - If the congestion duration in the previously originated
TLV was non null, it MAY originate a PCES TLV. Note that in some CONGESTION sub-TLV was non null, it MAY originate a CONGESTION sub-
particular cases it may be desired to originate a PCES TLV with the C TLV with the C bit cleared. Note that in some particular cases it may
bit cleared if the congestion duration was over estimated. be desired to originate a PCES TLV with the C bit cleared if the
congestion duration was over estimated.
The congestion duration allows reducing the amount of IS-IS flooding, The congestion duration allows a reduction in the amount of IS-IS
as only uncongested-to-congested state transitions are advertised. flooding, as only uncongested-to-congested state transitions need
advertised.
An implementation SHOULD support an appropriate dampening algorithm A PCE implementation SHOULD support an appropriate dampening
so as to dampen IS-IS flooding in order to not impact the IS-IS algorithm so as to dampen IS-IS flooding in order to not impact the
scalability. It is RECOMMENDED to introduce some hysteresis for IS-IS scalability. It is RECOMMENDED to introduce some hysteresis for
congestion state transition, so as to avoid state oscillations that congestion state transition, so as to avoid state oscillations that
may impact IS-IS performances. For instance two thresholds MAY be may impact IS-IS performance. For instance two thresholds MAY be
configured: a resource congestion upper-threshold and a resource configured: a resource congestion upper-threshold and a resource
congestion lower-threshold. An LSR enters the congested state when congestion lower-threshold. An LSR enters the congested state when
the CPU load reaches the upper threshold and leaves the congested the CPU load reaches the upper threshold and leaves the congested
state when the CPU load goes under the lower threshold. state when the CPU load goes under the lower threshold.
Upon receipt of an updated PCES TLV a PCC should take appropriate Upon receipt of an updated CONGESTION sub-TLV a PCC should take
actions. In particular, the PCC SHOULD stop sending requests to a appropriate actions. In particular, the PCC SHOULD stop sending
congested PCE, and SHOULD gradually start sending again requests to a requests to a congested PCE, and SHOULD gradually start sending again
no longer congested PCE. requests to a PCE that is no longer congested
7. Backward compatibility 6. Backward compatibility
The PCED and PCES TLVs defined in this document do not introduce any The PCED TLV defined in this document does not introduce any
interoperability issue. interoperability issues.
An IS-IS router not supporting the PCED/PCES TLVs will just silently
ignore the TLV as specified in [IS-IS-CAP].
8. IANA considerations An IS-IS router not supporting the PCED TLV will just silently ignore
the TLV as specified in [IS-IS-CAP].
8.1. IS-IS sub-TLVs 7. IANA considerations
IANA will assign two new codepoints for the PCED and PCES sub-TLVs 7.1. IS-IS sub-TLV
carried within the IS-IS CAPABILITY TLV defined in [IS-IS-CAP].
Type Description Reference Once a registry for the IS-IS Router Capability TLV defined in
[IS-IS-CAP] will have been assigned, IANA will assign a new
TLV code-point for the PCED TLV carried within the Router Capability
TLV.
1 PCED [IS-IS-CAP] Value Sub-TLV References
2 PCES [IS-IS-CAP] ----- -------- ----------
5 PCED TLV (this document)
8.1.1 Sub-TLVs of the PCED sub-TLV 7.2. PCED sub-TLVs registry
IANA is requested to manage sub-TLV types for the PCED sub-TLV. The PCED TLV referenced above is constructed from sub-TLVs. Each sub-
TLV includes a 8-bit type identifier.
Five sub-TLVs types are defined for the PCED sub-TLV and should be The IANA is requested to create a new registry and manage TLV type
assigned by IANA: identifiers as follows:
Type Description Reference - TLV Type
- TLV Name
- Reference
1 PCE-ADDRESS This document This document defines five TLVs as follows (suggested values):
2 PATH-SCOPE This document
3 PCE-DOMAINS This document
4 PCE-DEST-DOMAINS This document
5 GENERAL-CAP This document
6 PATH-COMP-CAP This document
Sub-TLVs of the PCE-DOMAINS and and PCE-DEST-DOMAINS sub-TLVs Value TLV name References
----- -------- ----------
1 PCE-ADDRESS This document
2 PATH-SCOPE This document
3 PCE-DOMAINS This document
4 PCE-NEIG-DOMAINS This document
5 PCE-CAP-FLAGS This document
6 CONGESTION This document
Two sub-TLVs types are defined for the PCE-DOMAINS and PCE-DEST- New TLV type values may be allocated only by an IETF Consensus
DOMAINS sub-TLVs and should be assigned by IANA: action.
Type Description Reference 7.3. PCE Capability Flags registry
1 Area ID This document This document provides new capability bit flags, which are present
2 AS Number This document in the PCE-CAP-FLAGS TLV referenced in section 4.1.5.
Sub-TLV of the PATH-COMP-CAP sub-TLV 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
notation starting at zero, and continuing at least through 31, with
the most significant bit as bit zero.
Three sub-TLV types are defined for the PATH-COMP-CAP sub-TLV and The same registry is defined for OSPF based PCE discovery [PCED-OSPF].
should be assigned by IANA: A single registry must be defined for both protocols.
Type Description Reference New bit numbers may be allocated only by an IETF Consensus action.
1 Objective Functions This document Each bit should be tracked with the following qualities:
2 Opaque Objective Function This document
3 Switch Caps sub-TLV This document
8.1.2 Sub-TLVs of the PCES sub-TLV - Bit number
- Defining RFC
- Capability Description
IANA is requested to manage sub-TLV types for the PCES TLV. Several bits are defined in this document. Here are the suggested
values:
Type Description Reference Bit Capability Description
1 PCE-ADDRESS This document 0 GMPLS link constraints
2 CONGESTION This document 1 Bidirectional paths
2 PSC paths
3 TDM paths
4 LSC paths
5 FSC paths
6 Diverse paths
7 Load-balanced paths
8 Synchronized computation
9 Multiple objective functions
10 Additive path constraints (e.g. max hop count)
11 Request prioritization
12 Multiple requests per message
8.2. Capability bits 8. Security Considerations
IANA is requested to manage the space of the General Capabilities This document defines IS-IS extensions for PCE discovery within an
32-bit flag and the Path Computation Capabilities 32-bit flag defined administrative domain. Hence the security of the PCE discovery relies
in this document, numbering them in the usual IETF notation starting on the security of IS-IS.
at zero and continuing through 31.
New bit numbers may be allocated only by an IETF Consensus action.
Each bit should be tracked with the following qualities:
- Bit number
- Defining RFC
- Name of bit
Currently two bits are defined in the General Capabilities flag. Here Mechanisms defined to ensure authenticity and integrity of IS-IS LSPs
are the suggested values: [RFC3567], and their TLVs, can be used to secure the PCED TLV as well.
-0: Support for Request prioritization.
-1: Support for multiple messages within the same request message
Currently seven bits are defined in the Path Computation Capabilities IS-IS provides no mechanism for protecting the privacy of LSAs, and
flag. Here are the suggested values: in particular the privacy PCE discovery information.
-0: Capability to handle GMPLS Constraints 9. Manageability Considerations
-1: Capability to compute bidirectional paths
-2: Capability to compute link/node/SRLG diverse paths
-3: Capability to compute load-balanced paths
-4: Capability to compute a set of paths in a
synchronized Manner
-5: Support for multiple objective function
-6: Capability to handle path constraints (e.g. hop count, metric
bound)
9. Security Considerations Manageability considerations for PCE Discovery are addressed in
section 4.10 of [RFC4674].
Any new security issues raised by the procedures in this document 9.1. Control of Policy and Functions
depend upon the opportunity for LSPs to be snooped, the
ease/difficulty of which has not been altered. As the LSPs may now
contain additional information regarding PCE capabilities, this
new information would also become available. Mechanisms defined to
secure ISIS Link State PDUs [RFC3567], and their TLVs, can be used to
secure PCED and PCES TLVs as well.
10. Manageability Considerations Requirements on the configuration of PCE discovery parameters on PCCs
and PCEs are discussed in section 4.10.1 of [RFC4674].
Manageability considerations for PCE Discovery are addressed in Particularly, a PCE implementation SHOULD allow configuring the
section 4.10 of [RFC4674]. following parameters on the PCE:
-The PCE IPv4/IPv6 address(es) (see section 4.1.1)
-The PCE Scope, including the inter-domain functions (inter-
area, inter-AS, inter-layer), the preferences, and whether the
PCE can act as default PCE (see section 4.1.2)
-The PCE domains (see section 4.1.3)
-The PCE neighbour domains (see section 4.1.4)
-The PCE capabilities (see section 4.1.5)
11. Acknowledgments 9.2. Information and Data Model
We would like to thank Lucy Wong and Adrian Farrel for their useful A MIB module for PCE Discovery is defined in [PCED-MIB].
comments and suggestions.
12. References 9.3. Liveness Detection and Monitoring
12.1. Normative references PCE Discovery Protocol liveness detection relies upon OSPF liveness
detection. IS-IS already includes a liveness detection mechanism
(Hello PDUs), and PCE discovery does not require additional
capabilities.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Procedures defined in section 5 allow a PCC detecting when a PCE has
Requirement Levels", BCP 14, RFC 2119, March 1997. been deactivated, or is no longer reachable.
[RFC3667] Bradner, S., "IETF Rights in Contributions", BCP 78, RFC 9.4. Verify Correct Operations
3667, February 2004.
[BCP79] Bradner, S., "Intellectual Property Rights in IETF The correlation of information advertised against information
Technology", RFC 3979, March 2005. 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
number of dropped, corrupt, and rejected information elements are
stored in the PCED MIB.
[IS-IS] "Intermediate System to Intermediate System Intra-Domain 9.5. Requirements on Other Protocols and Functional Components
Routing Exchange Protocol " ISO 10589.
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and The IS-IS extensions defined in this documents does not imply any
dual environments", RFC 1195, December 1990. requirement on other protocols.
9.6. Impact on network operations
Frequent changes in PCE information, and particularly in PCE
congestion information, may have a significant impact on IS-IS and
might destabilize the operation of the network by causing the PCCs to
swap between PCEs.
As discussed in section 5, a PCE implementation SHOULD support an
appropriate dampening algorithm so as to dampen IS-IS flooding in
order to not impact the IS-IS scalability.
Also, as discussed in section 4.10.4 of [RFC4674], it MUST be
possible to apply at least the following controls:
- Configurable limit on the rate of announcement of changed
parameters at a PCE.
- Control of the impact on PCCs such as through discovery messages
rate-limiting.
- Configurable control of triggers that cause a PCC to swap to
another PCE.
10. Acknowledgments
We would like to thank Lucy Wong and Adrian Farrel for their useful
comments and suggestions.
11. References
11.1. Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
skipping to change at page 21, line 5 skipping to change at page 19, line 7
RFC4674, October 2006. RFC4674, October 2006.
[RFC4205] Kompella, Rekhter, " IS-IS Extensions in Support of [RFC4205] Kompella, Rekhter, " IS-IS Extensions in Support of
Generalized Multi-Protocol Label Switching (GMPLS)", RFC4205, October Generalized Multi-Protocol Label Switching (GMPLS)", RFC4205, October
2005. 2005.
[RFC3567] Li, T. and R. Atkinson, "Intermediate System to [RFC3567] Li, T. and R. Atkinson, "Intermediate System to
Intermediate System (IS-IS) Cryptographic Authentication", RFC 3567, Intermediate System (IS-IS) Cryptographic Authentication", RFC 3567,
July 2003. July 2003.
12.2. Informative references 11.2. Informative references
[RFC4657] Ash, J., Le Roux, J.L., " PCE Communication Protocol [RFC4657] Ash, J., Le Roux, J.L., " PCE Communication Protocol
Generic Requirements", RFC4657, September 2006. Generic Requirements", RFC4657, September 2006.
[PCEP] Vasseur et al., "Path Computation Element (PCE) communication [PCEP] Vasseur, Le Roux, et al., “Path Computation Element (PCE)
Protocol (PCEP) - Version 1", draft-ietf-pce-pcep, work in progress. communication Protocol (PCEP) - Version 1”, draft-ietf-pce-pcep, work
in progress.
13. Editors' Addresses: [PCED-MIB] Stephan, E., "Definitions of Managed Objects for Path
Computation Element Discovery", draft-ietf-pce-disc-mib-00, work in
progress.
[PCED-OSPF] Le Roux, Vasseur, "OSPF protocol extensions for Path
Computation Element (PCE) Discovery", draft-ietf-pce-disco-proto-
ospf, work in progress.
12. Editors' Addresses:
Jean-Louis Le Roux (Editor) Jean-Louis Le Roux (Editor)
France Telecom France Telecom
2, avenue Pierre-Marzin 2, avenue Pierre-Marzin
22307 Lannion Cedex 22307 Lannion Cedex
FRANCE FRANCE
Email: jeanlouis.leroux@orange-ftgroup.com Email: jeanlouis.leroux@orange-ftgroup.com
Jean-Philippe Vasseur (Editor) Jean-Philippe Vasseur (Editor)
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts avenue 1414 Massachusetts avenue
Boxborough , MA - 01719 Boxborough , MA - 01719
USA USA
Email: jpv@cisco.com Email: jpv@cisco.com
14. Contributors' Adresses: 13. Contributors' Adresses:
Yuichi Ikejiri Yuichi Ikejiri
NTT Communications Corporation NTT Communications Corporation
1-1-6, Uchisaiwai-cho, Chiyoda-ku 1-1-6, Uchisaiwai-cho, Chiyoda-ku
Tokyo 100-8019 Tokyo 100-8019
JAPAN JAPAN
Email: y.ikejiri@ntt.com Email: y.ikejiri@ntt.com
Raymond Zhang Raymond Zhang
BT Infonet BT Infonet
2160 E. Grand Ave. 2160 E. Grand Ave.
El Segundo, CA 90025 El Segundo, CA 90025
USA USA
Email: raymond_zhang@infonet.com Email: raymond_zhang@bt-infonet.com
15. Intellectual Property Statement 14. Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
skipping to change at page 22, line 32 skipping to change at page 20, line 43
on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE
IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE
ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE. FOR A PARTICULAR PURPOSE.
Copyright Statement Copyright Statement
Copyright (C) The IETF Trust (2006). This document is subject to the Copyright (C) The IETF Trust (2007). This document is subject to the
rights, licenses and restrictions contained in BCP 78, and except as rights, licenses and restrictions contained in BCP 78, and except as
set forth therein, the authors retain all their rights. set forth therein, the authors retain all their rights.
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