< draft-ietf-pce-disco-proto-isis-06.txt   draft-ietf-pce-disco-proto-isis-07.txt >
Network Working Group J.L. Le Roux (Editor) Network Working Group J.L. Le Roux (Editor)
Internet Draft France Telecom Internet Draft France Telecom
Intended Status: Standard Track Intended Status: Standard Track
Expires: December 2007 J.P. Vasseur (Editor) Expires: March 2008 J.P. Vasseur (Editor)
Cisco System Inc. Cisco System Inc.
Yuichi Ikejiri Yuichi Ikejiri
NTT Communications NTT Communications
Raymond Zhang Raymond Zhang
BT Infonet BT Infonet
June 2007 September 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-06.txt draft-ietf-pce-disco-proto-isis-07.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 Task Force (IETF), its areas, and its working groups. Note that
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domain. domain.
Conventions used in this document Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Table of Contents Table of Contents
1. Terminology.................................................3 Terminology........................................................3
1. 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 Overload Information....................................6 3.1.2. PCE Overload Information....................................6
3.2. Flooding Scope..............................................6 3.2. Flooding Scope..............................................6
4. IS-IS Extensions............................................7 4. The IS-IS PCED Sub-TLV......................................6
4.1. The IS-IS PCED Sub-TLV......................................7 4.1. PCE-ADDRESS Sub-TLV.........................................7
4.1.1. PCE-ADDRESS Sub-TLV.........................................8 4.2. The PATH-SCOPE Sub-TLV......................................7
4.1.2. The PATH-SCOPE Sub-TLV......................................8 4.3. PCE-DOMAIN Sub-TLV..........................................9
4.1.3. PCE-DOMAIN Sub-TLV.........................................10 4.4. NEIG-PCE-DOMAIN Sub-TLV....................................10
4.1.4. NEIG-PCE-DOMAIN Sub-TLV....................................11 4.5. PCE-CAP-FLAGS Sub-TLV......................................11
4.1.5. PCE-CAP-FLAGS Sub-TLV......................................11 4.6. The OVERLOAD Sub-TLV.......................................11
4.1.6. The OVERLOAD Sub-TLV.......................................12 5. Elements of Procedure......................................12
5. Elements of Procedure......................................13 5.1. OVERLOAD Sub-TLV Specific Procedures.......................12
5.1.1. OVERLOAD Sub-TLV Specific Procedures.......................14 6. Backward Compatibility.....................................13
6. Backward Compatibility.....................................14 7. IANA Considerations........................................13
7. IANA Considerations........................................14 8. Security Considerations....................................13
7.1. IS-IS Sub-TLV..............................................14 9. Manageability Considerations...............................14
7.2. PCED Sub-TLVs registry.....................................15 9.1. Control of Policy and Functions............................14
8. Security Considerations....................................15 9.2. Information and Data Model.................................14
9. Manageability Considerations...............................16 9.3. Liveness Detection and Monitoring..........................14
9.1. Control of Policy and Functions............................16 9.4. Verify Correct Operations..................................14
9.2. Information and Data Model.................................16
9.3. Liveness Detection and Monitoring..........................16
9.4. Verify Correct Operations..................................16
9.5. Requirements on Other Protocols and Functional 9.5. Requirements on Other Protocols and Functional
Components...............................................16 Components...............................................14
9.6. Impact on Network Operations...............................16
10. Acknowledgments............................................17
11. References.................................................17
11.1. Normative References.......................................17
11.2. Informative References.....................................18
12. Editors' Addresses:........................................18
13. Contributors' Adresses:....................................18
14. Intellectual Property Statement............................19
1. Terminology 9.6. Impact on Network Operations...............................15
10. Acknowledgments............................................15
11. References.................................................15
11.1. Normative References.......................................15
11.2. Informative References.....................................16
12. Editors' Addresses:........................................16
13. Contributors' Adresses:....................................16
14. Intellectual Property Statement............................17
Terminology used in this document 1. Terminology
AS: Autonomous System. AS: Autonomous System.
IGP: Interior Gateway Protocol. Either of the two routing IGP: Interior Gateway Protocol. Either of the two routing
protocols Open Shortest Path First (OSPF) or Intermediate System protocols Open Shortest Path First (OSPF) or Intermediate System
to Intermediate system (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.
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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 PCE-Domain: In a PCE context this refers to any collection of
network elements within a common sphere of address management or network elements within a common sphere of address management or
path computational responsibility (referred to as "domain" in path computational responsibility (referred to as "domain" in
[RFC4655]). Examples of PCE-Domains include IGP areas and ASes. [RFC4655]). Examples of PCE-Domains include IGP areas and ASes.
This should be distinguished from an IS-IS routing domain as
This should be distinguished from an IS-IS routing domain as defined by [ISO].
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
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When PCCs are LSRs participating in the IGP (OSPF, IS-IS), and PCEs When PCCs are LSRs participating in the IGP (OSPF, IS-IS), and PCEs
are either LSRs or servers also participating in the IGP, an are either LSRs or servers also participating in the IGP, an
effective mechanism for PCE discovery within an IGP routing domain effective mechanism for PCE discovery within an IGP routing domain
consists of utilizing IGP advertisements. consists of utilizing IGP advertisements.
This document defines IS-IS extensions to allow a PCE in an IS-IS This document defines IS-IS extensions to allow a PCE in an IS-IS
routing domain to advertise its location along with some information routing domain to advertise its location along with some information
useful to a PCC 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 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 overload 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 PCE Discovery (PCED)) to This document defines a new sub-TLV (named PCE Discovery (PCED)) to
be carried within the IS-IS Router Capability TLV ([IS-IS-CAP]). be carried within the IS-IS Router Capability TLV ([IS-IS-CAP]).
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- The set of one or more PCE-Domain(s) into which the PCE has - The set of one or more PCE-Domain(s) into which the PCE has
visibility and can compute paths; visibility and can compute paths;
- The set of one or more neighbor PCE-Domain(s) towards which a PCE - The set of one or more neighbor PCE-Domain(s) towards which a PCE
can compute paths; can compute paths;
- A set of communication capabilities (e.g. support for request - A set of communication capabilities (e.g. support for request
prioritization) and path computation specific capabilities prioritization) and path computation specific capabilities
(e.g. supported constraints). (e.g. supported constraints).
Optional elements to describe more complex capabilities may also be
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 Overload Information 3.1.2. PCE Overload Information
The PCE Overload Information is optional and can be used to report The PCE Overload Information is optional and can be used to report
a PCE's overload state in order to discourage the PCCs to send new a PCE's overload state in order to discourage the PCCs to send new
path computation requests. path computation requests.
A PCE may decide to clear the overload state according to local A PCE may decide to clear the overload state according to local
implementation triggers (e.g. CPU utilization, average queue length implementation triggers (e.g. CPU utilization, average queue length
below some pre-defined thresholds). The rate at which a PCE status below some pre-defined thresholds). The rate at which a PCE status
change is advertised MUST NOT impact by any means the IGP change is advertised MUST NOT impact by any means the IGP
scalability. Particular attention should be given on procedures to scalability. Particular attention should be given on procedures to
avoid state oscillations. 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 a single L1 area, a L1 area and the L2 sub-domain, or the entire be a single L1 area, a L1 area and the L2 sub-domain, or the entire
IS-IS routing domain. IS-IS routing domain.
4. IS-IS Extensions 4. The IS-IS PCED Sub-TLV
4.1. The IS-IS PCED Sub-TLV
The IS-IS PCED sub-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 sub-TLV and its sub-TLVs is 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 comprised of 1 octet for the type, 1 [RFC3784]. That is, the TLV is comprised 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 octets.
The IS-IS PCED sub-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. Six sub-TLVs are defined:
Currently six sub-TLVs are defined (suggested type values to be
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-DOMAIN sub-TLV 3 variable PCE-DOMAIN sub-TLV
4 variable NEIG-PCE-DOMAIN sub-TLV 4 variable NEIG-PCE-DOMAIN sub-TLV
5 variable PCE-CAP-FLAGS sub-TLV 5 variable PCE-CAP-FLAGS sub-TLV
6 1 OVERLOAD sub-TLV 6 1 OVERLOAD sub-TLV
The PCE-ADDRESS and PATH-SCOPE sub-TLVs MUST always be present within The PCE-ADDRESS and PATH-SCOPE sub-TLVs MUST always be present within
the PCED sub-TLV. the PCED sub-TLV.
The PCE-DOMAIN and NEIG-PCE-DOMAIN sub-TLVs are optional. They The PCE-DOMAIN and NEIG-PCE-DOMAIN sub-TLVs are optional. They
MAY be present in the PCED sub-TLV to facilitate selection of inter- MAY be present in the PCED sub-TLV to facilitate selection of inter-
domain PCEs. domain PCEs.
The PCE-CAP-FLAGS sub-TLV is optional and MAY be present in the PCED The PCE-CAP-FLAGS sub-TLV is optional and MAY be present in the PCED
sub-TLV to facilitate the PCE selection process. sub-TLV to facilitate the PCE selection process.
The OVERLOAD sub-TLV is optional and MAY be present in the PCED sub- The OVERLOAD sub-TLV is optional and MAY be present in the PCED sub-
TLV, to indicate a PCE's processing congestion state. TLV, to indicate a PCE's processing overload 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 PCE information.
The PCED sub-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].
No additional sub-TLVs will be added to the PCED TLV in the future.
If a future application requires advertising additional PCE
information in IS-IS, this will not be carried in the CAPABILITY TLV.
The following sub-sections describe the sub-TLVs which may be carried The following sub-sections describe the sub-TLVs which may be carried
within the PCED sub-TLV. within the PCED sub-TLV.
4.1.1. PCE-ADDRESS Sub-TLV 4.1. 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 sub-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. If it appears more than once only the first occurrence MUST be type. If it appears more than once only the first occurrence MUST be
processed and other MUST be ignored. processed and other MUST be ignored.
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: 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
4.1.2. The PATH-SCOPE Sub-TLV 4.2. 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 sub-TLV. There MUST be exactly one instance of the PATH-SCOPE PCED sub-TLV. There MUST be exactly one instance of the PATH-SCOPE
sub-TLV within each PCED sub-TLV. If it appears more than once only sub-TLV within each PCED sub-TLV. If it appears more than once only
the first occurrence MUST be processed and other MUST be ignored. the first occurrence MUST be processed and other MUST be ignored.
The PATH-SCOPE sub-TLV contains a set of bit flags indicating the The PATH-SCOPE sub-TLV contains a set of bit flags indicating the
supported path scopes, and four fields indicating PCE preferences. supported path scopes, and four fields indicating PCE preferences.
The PATH-SCOPE sub-TLV has the following format: The PATH-SCOPE sub-TLV has the following format:
TYPE: To be assigned by IANA (Suggested value =2) TYPE: 2
LENGTH: 3 LENGTH: 3
VALUE: This comprises a one-octet flags field where flag VALUE: This comprises a one-octet flags field where flag
represents a supported path scope, followed by a 2-octets represents a supported path scope, followed by a 2-octets
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|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
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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-DOMAIN Sub-TLV 4.3. PCE-DOMAIN Sub-TLV
The PCE-DOMAIN sub-TLV specifies a PCE-Domain (areas and/or ASes) The PCE-DOMAIN sub-TLV specifies a PCE-Domain (areas and/or ASes)
where the PCE has topology visibility and through which the PCE can where the PCE has topology visibility and through which the PCE can
compute paths. compute paths.
The PCE-DOMAIN 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).
A PCED sub-TLV MAY include multiple PCE-DOMAIN sub-TLVs when the PCE A PCED sub-TLV MAY include multiple PCE-DOMAIN sub-TLVs when the PCE
has visibility in multiple PCE-Domains. has visibility in multiple PCE-Domains.
The PCE-DOMAIN sub-TLV has the following format: The PCE-DOMAIN sub-TLV has the following format:
TYPE: To be assigned by IANA (Suggested value =3) TYPE: 3
LENGTH: Variable LENGTH: Variable
VALUE: This is comprised of one octet indicating the domain-type VALUE: This is comprised of one octet indicating the domain-type
(area ID or AS Number) and a variable length IS-IS area ID or a 32 (area ID or AS Number) and a variable length IS-IS area ID or a 32
bits AS number, identifying a PCE-domain where the PCE has visibility. bits AS number, identifying a PCE-domain where the PCE has visibility.
Two domain types are defined: Two domain types are defined:
1 Area ID 1 Area ID
2 AS Number 2 AS Number
The Area ID is the area address as defined in [ISO]. The Area ID is the area address as defined in [ISO].
When coded in two octets (which is the current defined format as the When coded in two octets (which is the current defined format as the
time of writing this document), the AS Number field MUST have its time of writing this document), the AS Number field MUST have its
left two octets set to 0. left two octets set to 0.
4.1.4. NEIG-PCE-DOMAIN Sub-TLV 4.4. NEIG-PCE-DOMAIN Sub-TLV
The NEIG-PCE-DOMAIN sub-TLV specifies a neighbour PCE-domain (area, The NEIG-PCE-DOMAIN sub-TLV specifies a neighbour PCE-domain (area,
AS) toward which a PCE can compute paths. It means that the PCE can AS) toward which a PCE can compute paths. It means that the PCE can
take part in the computation of inter-domain TE LSPs whose path take part in the computation of inter-domain TE LSPs whose path
transits this neighbour PCE-domain. transits this neighbour PCE-domain.
A PCED sub-TLV MAY include several NEIG-PCE-DOMAIN sub-TLVs when the A PCED sub-TLV MAY include several NEIG-PCE-DOMAIN sub-TLVs when the
PCE can compute paths towards several neighbour PCE-domains. PCE can compute paths towards several neighbour PCE-domains.
The NEIG-PCE-DOMAIN sub-TLV has the same format as the PCE-DOMAIN The NEIG-PCE-DOMAIN sub-TLV has the same format as the PCE-DOMAIN
sub-TLV: sub-TLV:
TYPE: To be assigned by IANA (Suggested value =4) TYPE: 4
LENGTH: Variable LENGTH: Variable
VALUE: This comprises one octet indicating the domain-type (area ID 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 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 number, identifying a PCE-domain towards which the PCE can compute
paths. paths.
Two domain types are defined: Two domain types are defined:
1 Area ID 1 Area ID
2 AS Number 2 AS Number
The Area ID is the area address as defined in [ISO]. The Area ID is the area address as defined in [ISO].
When coded in two octets (which is the current defined format as the When coded in two octets (which is the current defined format as the
time of writing this document), the AS Number field MUST have its time of writing this document), the AS Number field MUST have its
first two octets set to 0. first two octets set to 0.
The NEIG-PCE-DOMAIN sub-TLV MUST be present if the R bit is set and The NEIG-PCE-DOMAIN sub-TLV MUST be present 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.
4.1.5. PCE-CAP-FLAGS Sub-TLV 4.5. PCE-CAP-FLAGS Sub-TLV
The PCE-CAP-FLAGs sub-TLV is an optional sub-TLV used to indicate The PCE-CAP-FLAGs sub-TLV is an optional sub-TLV used to indicate
PCEP related capabilities. It MAY be present within the PCED sub-TLV. PCEP related capabilities. It MAY be present within the PCED sub-TLV.
It MUST NOT be present more than once. If it appears more than once It MUST NOT be present more than once. If it appears more than once
only the first occurrence MUST be processed and other MUST be ignored. only the first occurrence MUST be processed and other MUST be ignored.
The value field of the PCE-CAP-FLAGS sub-TLV is made up of an array The value field of the PCE-CAP-FLAGS sub-TLV is made up of an array
of units of 32 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 PCE-CAP-FLAGS 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: 5
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.
The PCE capability registry is managed by IANA, it is common The PCE capability registry is managed by IANA, it is common
with OSPF and defined in [PCED-OSPF]. with OSPF and defined in [PCED-OSPF].
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 OVERLOAD Sub-TLV 4.6. The OVERLOAD Sub-TLV
The CONGESTION sub-TLV is used to indicate that a PCE is experiencing The OVERLOAD sub-TLV is used to indicate that a PCE is experiencing a
a processing congestion state and may optionally include expected PCE processing overload state and may optionally include expected PCE
congestion duration. overload duration.
The CONGESTION sub-TLV is optional, it MAY be carried within the PCED The OVERLOAD sub-TLV is optional, it MAY be carried within the PCED
sub-TLV. It MUST NOT be present more than once. If it appears more sub-TLV. It MUST NOT be present more than once. If it appears more
than once only the first occurrence MUST be processed and other MUST than once only the first occurrence MUST be processed and other MUST
be ignored. be ignored.
The format of the CONGESTION sub-TLV is as follows: The format of the OVERLOAD sub-TLV is as follows:
TYPE: To be assigned by IANA (Suggested value =6) TYPE: 6
LENGTH: 1 LENGTH: 1
VALUE: This comprises a one octet of bit flags indicating the VALUE: This comprises a one octet of bit flags indicating the
overload status. Currently only the first flag is defined. overload status. Currently only the first flag is defined.
Here is the TLV structure Here is the TLV structure
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|C| Reserved| |C| Reserved|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Value Value
-C bit: When set this indicates that the PCE is overloaded -C bit: When set this indicates that the PCE is overloaded
and cannot accept any new request. When cleared this and cannot accept any new request. When cleared this
indicates that the PCE is not overloaded and can indicates that the PCE is not overloaded and can
accept new requests. accept new requests.
5. Elements of Procedure 5. Elements of Procedure
The PCED sub-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]. As such, elements of procedures are inherited defined in [IS-IS-CAP]. As such, elements of procedures are inherited
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no longer IP connectivity to the PCE node. no longer IP connectivity to the PCE node.
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. OVERLOAD Sub-TLV Specific Procedures 5.1. OVERLOAD Sub-TLV Specific Procedures
When a PCE enters into an overload state, the conditions of which are When a PCE enters into an overload state, the conditions of which are
implementation dependent, a new IS-IS LSP with an OVERLOAD sub-TLV implementation dependent, a new IS-IS LSP with an OVERLOAD sub-TLV
with the C bit set MAY be generated. with the C bit set MAY be generated.
When a PCE exists from an overload state, the conditions of which are When a PCE exists from an overload state, the conditions of which are
implementation dependent (e.g. CPU utilization, average queue length implementation dependent (e.g. CPU utilization, average queue length
below some pre-defined thresholds), a new IS-IS LSP with an OVERLOAD below some pre-defined thresholds), a new IS-IS LSP with an OVERLOAD
sub-TLV with the C bit cleared SHOULD be generated, if an OVERLOAD sub-TLV with the C bit cleared SHOULD be generated, if an OVERLOAD
sub-TLV with the C bit set had previously been generated. sub-TLV with the C bit set had previously been generated.
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6. Backward Compatibility 6. Backward Compatibility
The PCED sub-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 sub-TLV will just silently An IS-IS router not supporting the PCED sub-TLV will just silently
ignore 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
Once a registry for the IS-IS Router Capability sub-TLVs, defined in Once a registry for the IS-IS Router Capability sub-TLVs, defined in
[IS-IS-CAP] has been assigned, IANA will assign a new sub-TLV code- [IS-IS-CAP] has been assigned, IANA will assign a new sub-TLV code-
point for the PCED sub-TLV carried within the Router Capability TLV. point for the PCED sub-TLV carried within the Router Capability TLV.
Value Sub-TLV References Value Sub-TLV References
----- -------- ---------- ----- -------- ----------
5 PCED sub-TLV (this document) 5 PCED sub-TLV (this document)
7.2. PCED Sub-TLVs registry
The PCED sub-TLV referenced above is constructed from sub-TLVs. Each
sub-TLV includes a 8-bit type identifier.
The IANA is requested to create a new sub-registry of the IS-IS
Router Capability sub-TLVs registry, named the "PCED sub-TLVs"
registry, and manage sub-TLV type identifiers as follows:
- sub-TLV Type
- sub-TLV Name
- Reference
This document defines five sub-TLVs as follows (suggested values):
Sub-TLV Sub-TLV
Type name References
----- -------- ----------
1 PCE-ADDRESS This document
2 PATH-SCOPE This document
3 PCE-DOMAIN This document
4 NEIG-PCE-DOMAIN This document
5 PCE-CAP-FLAGS This document
6 OVERLOAD This document
New sub-TLV type values may be allocated only by an IETF Consensus
action.
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 sub-TLV as [RFC3567], and their TLVs, can be used to secure the PCED sub-TLV as
well. well.
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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 document do not imply any The IS-IS extensions defined in this document do not imply any
requirement on other protocols. requirement on other protocols.
9.6. Impact on Network Operations 9.6. Impact on Network Operations
Frequent changes in PCE information, and particularly in PCE Frequent changes in PCE information, and particularly in PCE overload
overload information, may have a significant impact on IS-IS and information, may have a significant impact on IS-IS and might
might destabilize the operation of the network by causing the PCCs to destabilize the operation of the network by causing the PCCs to swap
swap between PCEs. between PCEs.
As discussed in section 5.1, 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.
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