draft-ietf-pce-hierarchy-extensions-04.txt   draft-ietf-pce-hierarchy-extensions-05.txt 
PCE Working Group F. Zhang PCE Working Group F. Zhang
Internet-Draft Q. Zhao Internet-Draft Q. Zhao
Intended status: Standards Track Huawei Intended status: Standards Track Huawei
Expires: September 6, 2018 O. Gonzalez de Dios Expires: January 16, 2019 O. Gonzalez de Dios
Telefonica I+D Telefonica I+D
R. Casellas R. Casellas
CTTC CTTC
D. King D. King
Old Dog Consulting Old Dog Consulting
March 5, 2018 July 15, 2018
Extensions to Path Computation Element Communication Protocol (PCEP) for Extensions to Path Computation Element Communication Protocol (PCEP) for
Hierarchical Path Computation Elements (PCE) Hierarchical Path Computation Elements (PCE)
draft-ietf-pce-hierarchy-extensions-04 draft-ietf-pce-hierarchy-extensions-05
Abstract Abstract
The Hierarchical Path Computation Element (H-PCE) architecture RFC The Hierarchical Path Computation Element (H-PCE) architecture RFC
6805, provides a mechanism to allow the optimum sequence of domains 6805, provides a mechanism to allow the optimum sequence of domains
to be selected, and the optimum end-to-end path to be derived through to be selected, and the optimum end-to-end path to be derived through
the use of a hierarchical relationship between domains. the use of a hierarchical relationship between domains.
This document defines the Path Computation Element Protocol (PCEP) This document defines the Path Computation Element Protocol (PCEP)
extensions for the purpose of implementing necessary Hierarchical PCE extensions for the purpose of implementing necessary Hierarchical PCE
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 6, 2018. This Internet-Draft will expire on January 16, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 5 1.3. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Requirements for H-PCE . . . . . . . . . . . . . . . . . . . 5 2. Requirements for H-PCE . . . . . . . . . . . . . . . . . . . 5
2.1. Path Computation Request . . . . . . . . . . . . . . . . 5 2.1. Path Computation Request . . . . . . . . . . . . . . . . 5
2.1.1. Qualification of PCEP Requests . . . . . . . . . . . 5 2.1.1. Qualification of PCEP Requests . . . . . . . . . . . 6
2.1.2. Multi-domain Objective Functions . . . . . . . . . . 6 2.1.2. Multi-domain Objective Functions . . . . . . . . . . 6
2.1.3. Multi-domain Metrics . . . . . . . . . . . . . . . . 6 2.1.3. Multi-domain Metrics . . . . . . . . . . . . . . . . 7
2.2. Parent PCE Capability Advertisement . . . . . . . . . . . 7 2.2. Parent PCE Capability Advertisement . . . . . . . . . . . 7
2.3. PCE Domain Discovery . . . . . . . . . . . . . . . . . . 7 2.3. PCE Domain Discovery . . . . . . . . . . . . . . . . . . 7
2.4. Domain Diversity . . . . . . . . . . . . . . . . . . . . 7 2.4. Domain Diversity . . . . . . . . . . . . . . . . . . . . 8
3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 8 3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. OPEN object . . . . . . . . . . . . . . . . . . . . . . . 8 3.1. OPEN object . . . . . . . . . . . . . . . . . . . . . . . 8
3.1.1. H-PCE capability TLV . . . . . . . . . . . . . . . . 8 3.1.1. H-PCE capability TLV . . . . . . . . . . . . . . . . 8
3.1.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 9 3.1.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 9
3.2. RP object . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2. RP object . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.1. H-PCE-FLAG TLV . . . . . . . . . . . . . . . . . . . 10 3.2.1. H-PCE-FLAG TLV . . . . . . . . . . . . . . . . . . . 10
3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 10 3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 11
3.3. Objective Functions . . . . . . . . . . . . . . . . . . . 11 3.3. Objective Functions . . . . . . . . . . . . . . . . . . . 11
3.3.1. OF Codes . . . . . . . . . . . . . . . . . . . . . . 11 3.3.1. OF Codes . . . . . . . . . . . . . . . . . . . . . . 11
3.3.2. OF Object . . . . . . . . . . . . . . . . . . . . . . 12 3.3.2. OF Object . . . . . . . . . . . . . . . . . . . . . . 13
3.4. Metric Object . . . . . . . . . . . . . . . . . . . . . . 12 3.4. Metric Object . . . . . . . . . . . . . . . . . . . . . . 13
3.5. SVEC Object . . . . . . . . . . . . . . . . . . . . . . . 13 3.5. SVEC Object . . . . . . . . . . . . . . . . . . . . . . . 14
3.6. PCEP-ERROR object . . . . . . . . . . . . . . . . . . . . 13 3.6. PCEP-ERROR object . . . . . . . . . . . . . . . . . . . . 14
3.6.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . . 13 3.6.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . . 14
3.7. NO-PATH Object . . . . . . . . . . . . . . . . . . . . . 14 3.7. NO-PATH Object . . . . . . . . . . . . . . . . . . . . . 15
4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . . 14 4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . . 15
4.1. OPEN Procedure between Child PCE and Parent PCE . . . . . 14 4.1. OPEN Procedure between Child PCE and Parent PCE . . . . . 15
4.2. Procedure to obtain Domain Sequence . . . . . . . . . . . 15 4.2. Procedure to obtain Domain Sequence . . . . . . . . . . . 16
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 15 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 16
6. Manageability Considerations . . . . . . . . . . . . . . . . 16 6. Manageability Considerations . . . . . . . . . . . . . . . . 17
6.1. Control of Function and Policy . . . . . . . . . . . . . 16 6.1. Control of Function and Policy . . . . . . . . . . . . . 17
6.1.1. Child PCE . . . . . . . . . . . . . . . . . . . . . . 17 6.1.1. Child PCE . . . . . . . . . . . . . . . . . . . . . . 17
6.1.2. Parent PCE . . . . . . . . . . . . . . . . . . . . . 17 6.1.2. Parent PCE . . . . . . . . . . . . . . . . . . . . . 18
6.1.3. Policy Control . . . . . . . . . . . . . . . . . . . 17 6.1.3. Policy Control . . . . . . . . . . . . . . . . . . . 18
6.2. Information and Data Models . . . . . . . . . . . . . . . 17 6.2. Information and Data Models . . . . . . . . . . . . . . . 18
6.3. Liveness Detection and Monitoring . . . . . . . . . . . . 18 6.3. Liveness Detection and Monitoring . . . . . . . . . . . . 18
6.4. Verify Correct Operations . . . . . . . . . . . . . . . . 18 6.4. Verify Correct Operations . . . . . . . . . . . . . . . . 19
6.5. Requirements On Other Protocols . . . . . . . . . . . . . 18 6.5. Requirements On Other Protocols . . . . . . . . . . . . . 19
6.6. Impact On Network Operations . . . . . . . . . . . . . . 18 6.6. Impact On Network Operations . . . . . . . . . . . . . . 19
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
7.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 19 7.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 19
7.2. H-PCE-CAPABILITY TLV Flags . . . . . . . . . . . . . . . 19 7.2. H-PCE-CAPABILITY TLV Flags . . . . . . . . . . . . . . . 20
7.3. Domain-ID TLV Domain type . . . . . . . . . . . . . . . . 19 7.3. Domain-ID TLV Domain type . . . . . . . . . . . . . . . . 20
7.4. H-PCE-FLAG TLV Flags . . . . . . . . . . . . . . . . . . 20 7.4. H-PCE-FLAG TLV Flags . . . . . . . . . . . . . . . . . . 20
7.5. OF Codes . . . . . . . . . . . . . . . . . . . . . . . . 20 7.5. OF Codes . . . . . . . . . . . . . . . . . . . . . . . . 21
7.6. METRIC Types . . . . . . . . . . . . . . . . . . . . . . 21 7.6. METRIC Types . . . . . . . . . . . . . . . . . . . . . . 21
7.7. New PCEP Error-Types and Values . . . . . . . . . . . . . 21 7.7. New PCEP Error-Types and Values . . . . . . . . . . . . . 22
7.8. New NO-PATH-VECTOR TLV Bit Flag . . . . . . . . . . . . . 22 7.8. New NO-PATH-VECTOR TLV Bit Flag . . . . . . . . . . . . . 22
7.9. SVEC Flag . . . . . . . . . . . . . . . . . . . . . . . . 22 7.9. SVEC Flag . . . . . . . . . . . . . . . . . . . . . . . . 22
8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
9. Implementation Status . . . . . . . . . . . . . . . . . . . . 23 9. Implementation Status . . . . . . . . . . . . . . . . . . . . 23
9.1. Inter-layer traffic engineering with H-PCE . . . . . . . 23 9.1. Inter-layer traffic engineering with H-PCE . . . . . . . 23
9.2. Telefonica Netphony (Open Source PCE) . . . . . . . . . . 24 9.2. Telefonica Netphony (Open Source PCE) . . . . . . . . . . 25
9.3. Implementation 3: H-PCE Proof of Concept developed by 9.3. Implementation 3: H-PCE Proof of Concept developed by
Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 26 Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 26
10. Contributing Authors . . . . . . . . . . . . . . . . . . . . 26 10. Contributing Authors . . . . . . . . . . . . . . . . . . . . 27
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
11.1. Normative References . . . . . . . . . . . . . . . . . . 27 11.1. Normative References . . . . . . . . . . . . . . . . . . 27
11.2. Informative References . . . . . . . . . . . . . . . . . 27 11.2. Informative References . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction 1. Introduction
The Path Computation Element communication Protocol (PCEP) provides
mechanisms for Path Computation Elements (PCEs) to perform path
computations in response to Path Computation Clients' (PCCs)
requests.
The capability to compute the routes of end-to-end inter-domain MPLS
Traffic Engineering (MPLS-TE) and GMPLS Label Switched Paths (LSPs)
is expressed as requirements in [RFC4105] and [RFC4216]. This
capability may be realized by a PCE [RFC4655]. The methods for
establishing and controlling inter-domain MPLS-TE and GMPLS LSPs are
documented in [RFC4726].
[RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can [RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can
be used for computing end-to-end paths for inter-domain MPLS Traffic be used for computing end-to-end paths for inter-domain MPLS Traffic
Engineering (TE) and GMPLS Label Switched Paths (LSPs). Engineering (TE) and GMPLS Label Switched Paths (LSPs).
Within the hierarchical PCE architecture, the parent PCE is used to Within the hierarchical PCE architecture, the parent PCE is used to
compute a multi-domain path based on the domain connectivity compute a multi-domain path based on the domain connectivity
information . A child PCE may be responsible for a single domain or information . A child PCE may be responsible for a single domain or
multiple domains, it is used to compute the intra-domain path based multiple domains, it is used to compute the intra-domain path based
on its own domain topology information. on its own domain topology information.
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* via requests to the child PCEs to discover if they contain the * via requests to the child PCEs to discover if they contain the
destination node; destination node;
* or any other methods. * or any other methods.
o Parent Traffic Engineering Database (TED) methods (section 4.4 of o Parent Traffic Engineering Database (TED) methods (section 4.4 of
[RFC6805]) [RFC6805])
o Learning of Domain connectivity and boundary nodes (BN) addresses. o Learning of Domain connectivity and boundary nodes (BN) addresses.
o Stateful PCE Operations. (Refer [I-D.ietf-pce-stateful-hpce])
1.2. Terminology 1.2. Terminology
This document uses the terminology defined in [RFC4655], [RFC5440] This document uses the terminology defined in [RFC4655], [RFC5440]
and the additional terms defined in section 1.4 of [RFC6805]. and the additional terms defined in section 1.4 of [RFC6805].
1.3. Requirements Language 1.3. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
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o Multi-domain Objective Functions (OF); o Multi-domain Objective Functions (OF);
o Multi-domain Metrics. o Multi-domain Metrics.
2.1.1. Qualification of PCEP Requests 2.1.1. Qualification of PCEP Requests
As described in section 4.8.1 of [RFC6805], the H-PCE architecture As described in section 4.8.1 of [RFC6805], the H-PCE architecture
introduces new request qualifications, which are: introduces new request qualifications, which are:
o It MUST be possible for a child PCE to indicate that a request it o It MUST be possible for a child PCE to indicate that a path
sends to a parent PCE should be satisfied by a domain sequence computation request sent to a parent PCE should be satisfied by a
only, that is, not by a full end-to-end path. This allows the domain sequence only, that is, not by a full end-to-end path.
child PCE to initiate a per-domain (PD) [RFC5152] or a backward This allows the child PCE to initiate a per-domain (PD) [RFC5152]
recursive path computation (BRPC) [RFC5441]. or a backward recursive path computation (BRPC) [RFC5441].
o As stated in [RFC6805], section 4.5, if a PCC knows the egress o As stated in [RFC6805], section 4.5, if a PCC knows the egress
domain, it can supply this information as the path computation domain, it can supply this information as the path computation
request. It SHOULD be possible to specify the destination domain request. It SHOULD be possible to specify the destination domain
information in a PCEP request, if it is known. information in a PCEP request, if it is known.
o It MAY be possible to indicate that the inter domain path computed o It MAY be possible to indicate that the inter domain path computed
by parent PCE should disallow domain re-entry. by parent PCE should disallow domain re-entry.
2.1.2. Multi-domain Objective Functions 2.1.2. Multi-domain Objective Functions
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also defined in this document. also defined in this document.
During the PCEP session establishment procedure, the parent PCE needs During the PCEP session establishment procedure, the parent PCE needs
to be capable of indicating the Objective Functions (OF) [RFC5541] to be capable of indicating the Objective Functions (OF) [RFC5541]
capability in the Open message. This capability information may then capability in the Open message. This capability information may then
be announced by child PCEs, and used for selecting the PCE when a PCC be announced by child PCEs, and used for selecting the PCE when a PCC
wants a path that satisfies one or multiple inter-domain objective wants a path that satisfies one or multiple inter-domain objective
functions. functions.
When a PCC requests a PCE to compute an inter-domain path, the PCC When a PCC requests a PCE to compute an inter-domain path, the PCC
needs also to be capable of indicating the new objective functions needs to be capable of indicating the new objective functions for
for inter-domain path. Note that a given child PCE may also act as a inter-domain path. Note that a given child PCE may also act as a
parent PCE. parent PCE (for some other child PCE).
For the reasons described previously, new OF codes need to be defined For the reasons described previously, new OF codes need to be defined
for the new inter-domain objective functions. Then the PCE can for the new inter-domain objective functions. Then the PCE can
notify its new inter-domain objective functions to the PCC by notify its new inter-domain objective functions to the PCC by
carrying them in the OF-list TLV which is carried in the OPEN object. carrying them in the OF-list TLV which is carried in the OPEN object.
The PCC can specify which objective function code to use, which is The PCC can specify which objective function code to use, which is
carried in the OF object when requesting a PCE to compute an inter- carried in the OF object when requesting a PCE to compute an inter-
domain path. domain path.
A parent PCE MUST be capable of ensuring homogeneity, across domains, A parent PCE MUST be capable of ensuring homogeneity, across domains,
when applying OF codes for strict OF intra-domain requests. when applying OF codes for strict OF intra-domain requests.
2.1.3. Multi-domain Metrics 2.1.3. Multi-domain Metrics
For inter-domain path computation, there are several path metrics of For inter-domain path computation, there are several path metrics of
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A parent PCE MUST be capable of ensuring homogeneity, across domains, A parent PCE MUST be capable of ensuring homogeneity, across domains,
when applying OF codes for strict OF intra-domain requests. when applying OF codes for strict OF intra-domain requests.
2.1.3. Multi-domain Metrics 2.1.3. Multi-domain Metrics
For inter-domain path computation, there are several path metrics of For inter-domain path computation, there are several path metrics of
interest. interest.
o Domain count (number of domains crossed); o Domain count (number of domains crossed);
o Border Node count. o Border Node count.
A PCC may be able to limit the number of domains crossed by applying A PCC may be able to limit the number of domains crossed by applying
a limit on these metrics. Details in section 3.3. a limit on these metrics. Details in Section 3.4.
2.2. Parent PCE Capability Advertisement 2.2. Parent PCE Capability Advertisement
Parent and child PCE relationships are likely to be configured. Parent and child PCE relationships are likely to be configured.
However, as mentioned in [RFC6805], it would assist network operators However, as mentioned in [RFC6805], it would assist network operators
if the child and parent PCEs could indicate their H-PCE capabilities. if the child and parent PCEs could indicate their H-PCE capabilities.
During the PCEP session establishment procedure, the child PCE needs During the PCEP session establishment procedure, the child PCE needs
to be capable of indicating to the parent PCE whether it requests the to be capable of indicating to the parent PCE whether it requests the
parent PCE capability or not. Also, during the PCEP session parent PCE capability or not. Also, during the PCEP session
establishment procedure, the parent PCE needs to be capable of establishment procedure, the parent PCE needs to be capable of
indicating whether its parent capability can be provided or not. indicating whether its parent capability can be provided or not.
A PCEP Speaker (Parent PCE or Child PCE or PCC) includes the "H-PCE A PCEP Speaker (Parent PCE or Child PCE or PCC) includes the "H-PCE
Capability" TLV, described in Section 3.1.1, in the OPEN Object to Capability" TLV, described in Section 3.1.1, in the OPEN Object to
advertise its support for PCEP extensions for H-PCE Capability. advertise its support for PCEP extensions for H-PCE Capability.
2.3. PCE Domain Discovery 2.3. PCE Domain Discovery
A PCE domain is a single domain with an associated PCE. Although it A PCE domain is a single domain with an associated PCE. Although it
is possible for a PCE to manage multiple domains. The PCE domain may is possible for a PCE to manage multiple domains simultaneously. The
be an IGP area or AS. PCE domain could be an IGP area or AS.
The PCE domain identifiers may be provided during the PCEP session The PCE domain identifiers MAY be provided during the PCEP session
establishment procedure. establishment procedure.
2.4. Domain Diversity 2.4. Domain Diversity
In a multi-domain environment, Domain Diversity is defined in In a multi-domain environment, Domain Diversity is defined in
[RFC6805]. A pair of paths are domain-diverse if they do not [RFC6805]. A pair of paths are domain-diverse if they do not
traverse any of the same transit domains. Domain diversity may be traverse any of the same transit domains. Domain diversity may be
maximized for a pair of paths by selecting paths that have the maximized for a pair of paths by selecting paths that have the
smallest number of shared domains. Path computation should smallest number of shared domains. Path computation should
facilitate the selection of domain diverse paths as a way to reduce facilitate the selection of domain diverse paths as a way to reduce
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OPEN object. This way, during PCEP session establishment, the H-PCE OPEN object. This way, during PCEP session establishment, the H-PCE
capability and Domain information can be advertised. capability and Domain information can be advertised.
3.1.1. H-PCE capability TLV 3.1.1. H-PCE capability TLV
The H-PCE-CAPABILITY TLV is an optional TLV associated with the OPEN The H-PCE-CAPABILITY TLV is an optional TLV associated with the OPEN
Object [RFC5440] to exchange H-PCE capability of PCEP speakers. Object [RFC5440] to exchange H-PCE capability of PCEP speakers.
Its format is shown in the following figure: Its format is shown in the following figure:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type= TBD1 | Length=4 | | Type= TBD1 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |I|R| | Flags |I|R|
+---------------------------------------------------------------+ +---------------------------------------------------------------+
Figure 1: H-PCE-CAPABILITY TLV format Figure 1: H-PCE-CAPABILITY TLV format
The type of the TLV is TBD1 (to be assigned by IANA) and it has a The type of the TLV is TBD1 (to be assigned by IANA) and it has a
fixed length of 4 octets. fixed length of 4 octets.
The value comprises a single field - Flags (32 bits): The value comprises a single field - Flags (32 bits):
R (Parent PCE Request bit): if set, will signal that the child PCE R (Parent PCE Request bit): if set, will signal that the child PCE
wishes to use the peer PCE as a parent PCE. wishes to use the peer PCE as a parent PCE.
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Capability not advertised). Capability not advertised).
3.1.2. Domain-ID TLV 3.1.2. Domain-ID TLV
The Domain-ID TLV when used in OPEN object identify the domain(s) The Domain-ID TLV when used in OPEN object identify the domain(s)
served by the PCE. The child PCE uses this mechanism to inform the served by the PCE. The child PCE uses this mechanism to inform the
domain information to the parent PCE. domain information to the parent PCE.
The Domain-ID TLV is defined below: The Domain-ID TLV is defined below:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type= TBD2 | Length | | Type= TBD2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain Type | Reserved | | Domain Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain ID | | Domain ID |
// // // //
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Domain-ID TLV format Figure 2: Domain-ID TLV format
The type of the TLV is TBD2 (to be assigned by IANA) and it has a The type of the TLV is TBD2 (to be assigned by IANA) and it has a
variable Length of the value portion. The value part comprises of - variable Length of the value portion. The value part comprises of -
Domain Type (8 bits): Indicates the domain type. Four types of Domain Type (8 bits): Indicates the domain type. Four types of
domain are currently defined: domain are currently defined:
* Type=1: the Domain ID field carries a 2-byte AS number. Padded * Type=1: the Domain ID field carries a 2-byte AS number. Padded
with trailing zeroes to a 4-byte boundary. with trailing zeros to a 4-byte boundary.
* Type=2: the Domain ID field carries a 4-byte AS number. * Type=2: the Domain ID field carries a 4-byte AS number.
* Type=3: the Domain ID field carries an 4-byte OSPF area ID. * Type=3: the Domain ID field carries an 4-byte OSPF area ID.
* Type=4: the Domain ID field carries [2-byte Area-Len, variable * Type=4: the Domain ID field carries (2-byte Area-Len, variable
length IS-IS area ID]. Padded with trailing zeroes to a 4-byte length IS-IS area ID). Padded with trailing zeros to a 4-byte
boundary. boundary.
Reserved: Zero at transmission; ignored at receipt. Reserved: Zero at transmission; ignored at receipt.
Domain ID (variable): Indicates an IGP Area ID or AS number. It Domain ID (variable): Indicates an IGP Area ID or AS number. It
can be 2 bytes, 4 bytes or variable length depending on the domain can be 2 bytes, 4 bytes or variable length depending on the domain
identifier used. It is padded with trailing zeroes to a 4-byte identifier used. It is padded with trailing zeros to a 4-byte
boundary. boundary.
In case a PCE serves more than one domain, multiple Domain-ID TLV is In case a PCE serves more than one domain, multiple Domain-ID TLV is
included for each domain it serves. included for each domain it serves.
3.2. RP object 3.2. RP object
3.2.1. H-PCE-FLAG TLV 3.2.1. H-PCE-FLAG TLV
The H-PCE-FLAG TLV is an optional TLV associated with the RP Object The H-PCE-FLAG TLV is an optional TLV associated with the RP Object
[RFC5440] to indicate the H-PCE path computation request and options. [RFC5440] to indicate the H-PCE path computation request and options.
Its format is shown in the following figure: Its format is shown in the following figure:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type= TBD3 | Length=4 | | Type= TBD3 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |D|S| | Flags |D|S|
+---------------------------------------------------------------+ +---------------------------------------------------------------+
Figure 3: H-PCE-FLAG TLV format Figure 3: H-PCE-FLAG TLV format
The type of the TLV is TBD3 (to be assigned by IANA) and it has a The type of the TLV is TBD3 (to be assigned by IANA) and it has a
fixed length of 4 octets. fixed length of 4 octets.
The value comprises a single field - Flags (32 bits): The value comprises a single field - Flags (32 bits):
S (Domain Sequence bit): if set, will signal that the child PCE S (Domain Sequence bit): if set, will signal that the child PCE
wishes to get only the domain sequence in the path computation wishes to get only the domain sequence in the path computation
reply. Refer section 3.7 of [RFC7897] for details. reply. Refer section 3.7 of [RFC7897] for details.
D (Disallow Domain Re-entry bit): if set, will signal that the D (Disallow Domain Re-entry bit): if set, will signal that the
computed path does not enter a domain more than once. computed path does not enter a domain more than once.
3.2.2. Domain-ID TLV 3.2.2. Domain-ID TLV
The usage of Domain-ID TLV carried in an OPEN object is used to The usage of Domain-ID TLV carried in an OPEN object is used to
indicate a (list of) managed domains and is described in section indicate a (list of) managed domains and is described in
3.1.2. This TLV when carried in a RP object, indicates the Section 3.1.2. This TLV when carried in a RP object, indicates the
destination domain ID. If a PCC knows the egress domain, it can destination domain ID. If a PCC knows the egress domain, it can
supply this information in the PCReq message. The format of this TLV supply this information in the PCReq message. The format and
is defined in Section 3.1.2. procedure of this TLV is defined in Section 3.1.2.
3.3. Objective Functions 3.3. Objective Functions
3.3.1. OF Codes 3.3.1. OF Codes
[RFC5541] defines a mechanism to specify an objective function that [RFC5541] defines a mechanism to specify an objective function that
is used by a PCE when it computes a path. Two new objective is used by a PCE when it computes a path. Two new objective
functions are defined for the H-PCE experiment. functions are defined for the H-PCE experiment.
o MTD o MTD
skipping to change at page 12, line 27 skipping to change at page 13, line 13
least number of common transit domains. least number of common transit domains.
3.3.2. OF Object 3.3.2. OF Object
The OF (Objective Function) object [RFC5541] is carried within a The OF (Objective Function) object [RFC5541] is carried within a
PCReq message so as to indicate the desired/required objective PCReq message so as to indicate the desired/required objective
function to be applied by the PCE during path computation. As per function to be applied by the PCE during path computation. As per
section 3.2 of [RFC5541] a single OF object may be included in a path section 3.2 of [RFC5541] a single OF object may be included in a path
computation request. computation request.
The new OF code described in section 3.3.1 are applicable at the The new OF code described in Section 3.3.1 are applicable at the
inter-domain level (parent), it is also necessary to specify the OF inter-domain level (parent), it is also necessary to specify the OF
code that may be applied at the intra-domain (child) path computation code that may be applied at the intra-domain (child) path computation
level. To accommodate this, the OF-List TLV (described in section level. To accommodate this, the OF-List TLV (described in section
2.1. of [RFC5541]) is included in the OF object as an optional TLV. 2.1. of [RFC5541]) is included in the OF object as an optional TLV.
OF-List TLV allow encoding of multiple OF codes. When this TLV is OF-List TLV allow encoding of multiple OF codes. When this TLV is
included inside the OF object, only the first OF-code in the OF-LIST included inside the OF object, only the first OF-code in the OF-LIST
TLV is considered. The parent PCE would use this OF code in the OF TLV is considered. The parent PCE MUST use this OF code in the OF
object when sending the intra domain path computation request to the object when sending the intra domain path computation request to the
child PCE. child PCE.
If the objective functions defined in this document are unknown/ If the objective functions defined in this document are unknown/
unsupported by a PCE, then the procedure as defined in [RFC5541] is unsupported by a PCE, then the procedure as defined in [RFC5541] is
followed. followed.
3.4. Metric Object 3.4. Metric Object
The METRIC object is defined in section 7.8 of [RFC5440], comprising The METRIC object is defined in section 7.8 of [RFC5440], comprising
skipping to change at page 13, line 11 skipping to change at page 13, line 45
o T=TBD6: Domain count metric (number of domains crossed); o T=TBD6: Domain count metric (number of domains crossed);
o T=TBD7: Border Node count metric (number of border nodes crossed). o T=TBD7: Border Node count metric (number of border nodes crossed).
The domain count metric type of the METRIC object encodes the number The domain count metric type of the METRIC object encodes the number
of domain crossed in the path. The border node count metric type of of domain crossed in the path. The border node count metric type of
the METRIC object encodes the number of border nodes in the path. the METRIC object encodes the number of border nodes in the path.
A PCC or child PCE MAY use these metric in PCReq message an inter- A PCC or child PCE MAY use these metric in PCReq message an inter-
domain path meeting the number of domain or border nodes requirement. domain path meeting the number of domain or border nodes requirement.
In this case, the B bit MUST be set to suggest a bound (a maximum) As per [RFC5440], in this case, the B bit is set to suggest a bound
for the metric that must not be exceeded for the PCC to consider the (a maximum) for the metric that must not be exceeded for the PCC to
computed path as acceptable. consider the computed path as acceptable.
A PCC or child PCE MAY also use this metric to ask the PCE to A PCC or child PCE MAY also use this metric to ask the PCE to
optimize the metric during inter-domain path computation. In this optimize the metric during inter-domain path computation. In this
case, the B flag MUST be cleared. case, the B flag is cleared.
The Parent PCE MAY use these metric in a PCRep message along with a The Parent PCE MAY use these metric in a PCRep message along with a
NO-PATH object in the case where the PCE cannot compute a path NO-PATH object in the case where the PCE cannot compute a path
meeting this constraint. A PCE MAY also use this metric to send the meeting this constraint. A PCE MAY also use this metric to send the
computed end to end metric in a reply message. computed end to end metric in a reply message.
3.5. SVEC Object 3.5. SVEC Object
[RFC5440] defines SVEC object which includes flags for the potential [RFC5440] defines SVEC object which includes flags for the potential
dependency between the set of path computation requests (Link, Node dependency between the set of path computation requests (Link, Node
skipping to change at page 13, line 43 skipping to change at page 14, line 29
o O (Domain diverse) bit - TBD12 : when set, this indicates that the o O (Domain diverse) bit - TBD12 : when set, this indicates that the
computed paths corresponding to the requests specified by the computed paths corresponding to the requests specified by the
following RP objects MUST NOT have any transit domain(s) in following RP objects MUST NOT have any transit domain(s) in
common. common.
The Domain Diverse O-bit can be used in Hierarchical PCE path The Domain Diverse O-bit can be used in Hierarchical PCE path
computation to compute synchronized domain diverse end to end path or computation to compute synchronized domain diverse end to end path or
diverse domain sequences. diverse domain sequences.
When domain diverse O bit is set, it is applied to the transit When domain diverse O bit is set, it is applied to the transit
domains. The other bit in SVEC object (N, L, S etc) is set, SHOULD domains. The other bit in SVEC object (N, L, S etc) MAY be set and
still be applied in the ingress and egress shared domain. MUST still be applied in the ingress and egress shared domain.
3.6. PCEP-ERROR object 3.6. PCEP-ERROR object
3.6.1. Hierarchy PCE Error-Type 3.6.1. Hierarchy PCE Error-Type
A new PCEP Error-Type is used for this H-PCE experiment and is A new PCEP Error-Type [RFC5440] is used for the H-PCE extension as
defined below: defined below:
+------------+------------------------------------------------------+ +------------+-----------------------------------------+
| Error-Type | Meaning | | Error-Type | Meaning |
+------------+------------------------------------------------------+ +------------+-----------------------------------------+
| TBD8 | H-PCE error | | TBD8 | H-PCE error |
| | Error-value=1: parent PCE capability | | | Error-value=1: parent PCE capability |
| | was not advertised | | | was not advertised |
| | Error-value=2: parent PCE capability | | | Error-value=2: parent PCE capability |
| | cannot be provided | | | cannot be provided |
+------------+------------------------------------------------------+ +------------+-----------------------------------------+
Figure 4: H-PCE error Figure 4: H-PCE error
3.7. NO-PATH Object 3.7. NO-PATH Object
To communicate the reason(s) for not being able to find a multi- To communicate the reason(s) for not being able to find a multi-
domain path or domain sequence, the NO-PATH object can be used in the domain path or domain sequence, the NO-PATH object can be used in the
PCRep message. [RFC5440] defines the format of the NO-PATH object. PCRep message. [RFC5440] defines the format of the NO-PATH object.
The object may contain a NO-PATH-VECTOR TLV to provide additional The object may contain a NO-PATH-VECTOR TLV to provide additional
information about why a path computation has failed. information about why a path computation has failed.
skipping to change at page 14, line 41 skipping to change at page 15, line 29
o Bit number TBD10: When set, the parent PCE indicates unresponsive o Bit number TBD10: When set, the parent PCE indicates unresponsive
child PCE(s); child PCE(s);
o Bit number TBD11: When set, the parent PCE indicates no available o Bit number TBD11: When set, the parent PCE indicates no available
resource available in one or more domain(s). resource available in one or more domain(s).
4. H-PCE Procedures 4. H-PCE Procedures
4.1. OPEN Procedure between Child PCE and Parent PCE 4.1. OPEN Procedure between Child PCE and Parent PCE
If a child PCE wants to use the peer PCE as a parent, it can set the If a child PCE wants to use the peer PCE as a parent, it MUST set the
R (parent PCE request flag) in the H-PCE-CAPABILITY TLV inside the R (parent PCE request flag) in the H-PCE-CAPABILITY TLV inside the
OPEN object carried in the Open message during the PCEP session OPEN object carried in the Open message during the PCEP session
creation procedure. initialization procedure.
If the parent PCE can provide the parent function to the peer PCE, it If the parent PCE can provide the parent function to the peer PCE, it
may set the I (parent PCE indication flag) in the H-PCE-CAPABILITY MUST set the I (parent PCE indication flag) in the H-PCE-CAPABILITY
TLV inside the OPEN object carried in the Open message during the TLV inside the OPEN object carried in the Open message during the
PCEP session creation procedure. PCEP session creation procedure.
The PCE may also report its list of domain IDs to the peer PCE by The child PCE MAY also report its list of domain IDs to the parent
specifying them in the Domain-ID TLVs in the OPEN object carried in PCE by specifying them in the Domain-ID TLVs in the OPEN object
the Open message during the PCEP session creation procedure. carried in the Open message during the PCEP session initialization
procedure.
The OF codes defined in this document can be carried in the OF-list The OF codes defined in this document can be carried in the OF-list
TLV of the OPEN object. If the OF-list TLV carries the OF codes, it TLV of the OPEN object. If the OF-list TLV carries the OF codes, it
means that the PCE is capable of implementing the corresponding means that the PCE is capable of implementing the corresponding
objective functions. This information can be used for selecting a objective functions. This information can be used for selecting a
proper parent PCE when a child PCE wants to get a path that satisfies proper parent PCE when a child PCE wants to get a path that satisfies
a certain objective function. a certain objective function.
When a specific child PCE sends a PCReq to a peer PCE that requires When a specific child PCE sends a PCReq to a peer PCE that requires
parental activity and H-PCE capability flags were not set in the parental activity and H-PCE capability flags were not set in the
skipping to change at page 15, line 46 skipping to change at page 16, line 32
domain path computation succeeds the parent PCE sends a PCRep message domain path computation succeeds the parent PCE sends a PCRep message
which carries the domain sequence in the ERO to the child PCE. Refer which carries the domain sequence in the ERO to the child PCE. Refer
[RFC7897] for more details about domain sub-objects in the ERO. [RFC7897] for more details about domain sub-objects in the ERO.
Otherwise it sends a PCReq message which carries the NO-PATH object Otherwise it sends a PCReq message which carries the NO-PATH object
to the child PCE. to the child PCE.
5. Error Handling 5. Error Handling
A PCE that is capable of acting as a parent PCE might not be A PCE that is capable of acting as a parent PCE might not be
configured or willing to act as the parent for a specific child PCE. configured or willing to act as the parent for a specific child PCE.
This fact could be determined when the child sends a PCReq that This fact could be determined when the child sends a PCReq that
requires parental activity, and could result in a negative response requires parental activity, and could result in a negative response
in a PCEP Error (PCErr) message and indicate the hierarchy PCE error- in a PCEP Error (PCErr) message and indicate the hierarchy PCE error-
type=TBD8 (H-PCE error) and suitable error-value. (section 3.5.1) type=TBD8 (H-PCE error) and suitable error-value. (Section 3.6)
Additionally, the parent PCE may fail to find the multi-domain path Additionally, the parent PCE may fail to find the multi-domain path
or domain sequence due to one or more of the following reasons: or domain sequence due to one or more of the following reasons:
o A child PCE cannot find a suitable path to the egress; o A child PCE cannot find a suitable path to the egress;
o The parent PCE do not hear from a child PCE for a specified time; o The parent PCE do not hear from a child PCE for a specified time;
o The objective functions specified in the path request cannot be o The objective functions specified in the path request cannot be
met. met.
In this case, the parent PCE MAY need to send a negative path In this case, the parent PCE MAY need to send a negative path
computation reply specifying the reason. This can be achieved by computation reply specifying the reason. This can be achieved by
including NO-PATH object in the PCRep message. Extension to NO-PATH including NO-PATH object in the PCRep message. Extension to NO-PATH
object is needed to include the aforementioned reasons described in object is needed to include the aforementioned reasons described in
section 3.6. Section 3.7.
6. Manageability Considerations 6. Manageability Considerations
General PCE and PCEP management considerations are discussed in General PCE and PCEP management considerations are discussed in
[RFC4655] and [RFC5440]. There are additional management [RFC4655] and [RFC5440]. There are additional management
considerations for H-PCE which are described in [RFC6805], and considerations for H-PCE which are described in [RFC6805], and
repeated in this section. repeated in this section.
The administrative entity responsible for the management of the The administrative entity responsible for the management of the
parent PCEs must be determined for the following cases: parent PCEs must be determined for the following cases:
skipping to change at page 19, line 24 skipping to change at page 20, line 10
----------------------------------------------- -----------------------------------------------
TBD1 H-PCE-CAPABILITY TLV This I-D TBD1 H-PCE-CAPABILITY TLV This I-D
TBD2 Domain-ID TLV This I-D TBD2 Domain-ID TLV This I-D
TBD3 H-PCE-FLAG TLV This I-D TBD3 H-PCE-FLAG TLV This I-D
7.2. H-PCE-CAPABILITY TLV Flags 7.2. H-PCE-CAPABILITY TLV Flags
This document requests that a new sub-registry, named " H-PCE- This document requests that a new sub-registry, named " H-PCE-
CAPABILITY TLV Flag Field", is created within the "Path Computation CAPABILITY TLV Flag Field", is created within the "Path Computation
Element Protocol (PCEP) Numbers" registry to manage the Flag field in Element Protocol (PCEP) Numbers" registry to manage the Flag field in
the H-PCE-CAPABILITY TLV of the PCEP OPEN object (class = 1). the H-PCE-CAPABILITY TLV of the PCEP OPEN object.
New values are to be assigned by Standards Action [RFC5226]. Each New values are to be assigned by Standards Action [RFC5226]. Each
bit should be tracked with the following qualities: bit should be tracked with the following qualities:
o Bit number (counting from bit 0 as the most significant bit) o Bit number (counting from bit 0 as the most significant bit)
o Capability description o Capability description
o Defining RFC o Defining RFC
skipping to change at page 20, line 17 skipping to change at page 20, line 47
1 2-byte AS number 1 2-byte AS number
2 4-byte AS number 2 4-byte AS number
3 4-byte OSPF area ID 3 4-byte OSPF area ID
4 Variable length IS-IS area ID 4 Variable length IS-IS area ID
7.4. H-PCE-FLAG TLV Flags 7.4. H-PCE-FLAG TLV Flags
This document requests that a new sub-registry, named "H-PCE-FLAGS This document requests that a new sub-registry, named "H-PCE-FLAGS
TLV Flag Field", is created within the "Path Computation Element TLV Flag Field", is created within the "Path Computation Element
Protocol (PCEP) Numbers" registry to manage the Flag field in the H- Protocol (PCEP) Numbers" registry to manage the Flag field in the H-
PCE-FLAGS TLV of the PCEP OPEN object (class = 1). New values are to PCE-FLAGS TLV of the PCEP RP object. New values are to be assigned
be assigned by Standards Action [RFC5226]. Each bit should be by Standards Action [RFC5226]. Each bit should be tracked with the
tracked with the following qualities: following qualities:
o Bit number (counting from bit 0 as the most significant bit) o Bit number (counting from bit 0 as the most significant bit)
o Capability description o Capability description
o Defining RFC o Defining RFC
The following values are defined in this document: The following values are defined in this document:
Bit Description Reference Bit Description Reference
----------------------------------------------- -----------------------------------------------
31 S (Domain This I.D. 31 S (Domain This I.D.
Sequence bit) Sequence bit)
skipping to change at page 27, line 34 skipping to change at page 28, line 7
Communication Protocol (PCEP)", RFC 5541, Communication Protocol (PCEP)", RFC 5541,
DOI 10.17487/RFC5541, June 2009, DOI 10.17487/RFC5541, June 2009,
<https://www.rfc-editor.org/info/rfc5541>. <https://www.rfc-editor.org/info/rfc5541>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References 11.2. Informative References
[RFC4105] Le Roux, J., Ed., Vasseur, J., Ed., and J. Boyle, Ed.,
"Requirements for Inter-Area MPLS Traffic Engineering",
RFC 4105, DOI 10.17487/RFC4105, June 2005,
<https://www.rfc-editor.org/info/rfc4105>.
[RFC4216] Zhang, R., Ed. and J. Vasseur, Ed., "MPLS Inter-Autonomous
System (AS) Traffic Engineering (TE) Requirements",
RFC 4216, DOI 10.17487/RFC4216, November 2005,
<https://www.rfc-editor.org/info/rfc4216>.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006, DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>. <https://www.rfc-editor.org/info/rfc4655>.
[RFC4726] Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for
Inter-Domain Multiprotocol Label Switching Traffic
Engineering", RFC 4726, DOI 10.17487/RFC4726, November
2006, <https://www.rfc-editor.org/info/rfc4726>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226, IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008, DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>. <https://www.rfc-editor.org/info/rfc5226>.
[RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS [RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS
Requirements for the Path Computation Element Requirements for the Path Computation Element
Communication Protocol (PCECP)", RFC 5376, Communication Protocol (PCECP)", RFC 5376,
DOI 10.17487/RFC5376, November 2008, DOI 10.17487/RFC5376, November 2008,
<https://www.rfc-editor.org/info/rfc5376>. <https://www.rfc-editor.org/info/rfc5376>.
skipping to change at page 28, line 29 skipping to change at page 29, line 18
Traffic Engineering Label Switched Paths", RFC 5441, Traffic Engineering Label Switched Paths", RFC 5441,
DOI 10.17487/RFC5441, April 2009, DOI 10.17487/RFC5441, April 2009,
<https://www.rfc-editor.org/info/rfc5441>. <https://www.rfc-editor.org/info/rfc5441>.
[RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the [RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the
Path Computation Element Architecture to the Determination Path Computation Element Architecture to the Determination
of a Sequence of Domains in MPLS and GMPLS", RFC 6805, of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
DOI 10.17487/RFC6805, November 2012, DOI 10.17487/RFC6805, November 2012,
<https://www.rfc-editor.org/info/rfc6805>. <https://www.rfc-editor.org/info/rfc6805>.
[RFC7470] Zhang, F. and A. Farrel, "Conveying Vendor-Specific [RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
Constraints in the Path Computation Element Communication Hardwick, "Path Computation Element Communication Protocol
Protocol", RFC 7470, DOI 10.17487/RFC7470, March 2015, (PCEP) Management Information Base (MIB) Module",
<https://www.rfc-editor.org/info/rfc7470>. RFC 7420, DOI 10.17487/RFC7420, December 2014,
<https://www.rfc-editor.org/info/rfc7420>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752, Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016, DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>. <https://www.rfc-editor.org/info/rfc7752>.
[RFC7897] Dhody, D., Palle, U., and R. Casellas, "Domain Subobjects [RFC7897] Dhody, D., Palle, U., and R. Casellas, "Domain Subobjects
for the Path Computation Element Communication Protocol for the Path Computation Element Communication Protocol
(PCEP)", RFC 7897, DOI 10.17487/RFC7897, June 2016, (PCEP)", RFC 7897, DOI 10.17487/RFC7897, June 2016,
skipping to change at page 29, line 9 skipping to change at page 29, line 45
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the "PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)", Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017, RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>. <https://www.rfc-editor.org/info/rfc8253>.
[I-D.ietf-pce-pcep-yang] [I-D.ietf-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
YANG Data Model for Path Computation Element YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", draft-ietf-pce-pcep- Communications Protocol (PCEP)", draft-ietf-pce-pcep-
yang-07 (work in progress), March 2018. yang-08 (work in progress), June 2018.
[I-D.ietf-pce-stateful-hpce] [I-D.ietf-pce-stateful-hpce]
Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., King, D., Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., King, D.,
and O. Dios, "Hierarchical Stateful Path Computation and O. Dios, "Hierarchical Stateful Path Computation
Element (PCE).", draft-ietf-pce-stateful-hpce-04 (work in Element (PCE).", draft-ietf-pce-stateful-hpce-05 (work in
progress), March 2018. progress), June 2018.
Authors' Addresses Authors' Addresses
Fatai Zhang Fatai Zhang
Huawei Huawei
Huawei Base, Bantian, Longgang District Huawei Base, Bantian, Longgang District
Shenzhen 518129 Shenzhen 518129
China China
EMail: zhangfatai@huawei.com EMail: zhangfatai@huawei.com
 End of changes. 57 change blocks. 
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