draft-ietf-pce-hierarchy-extensions-10.txt   draft-ietf-pce-hierarchy-extensions-11.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 5, 2019 O. Gonzalez de Dios Expires: December 2, 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 4, 2019 June 1, 2019
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-10 draft-ietf-pce-hierarchy-extensions-11
Abstract Abstract
The Hierarchical Path Computation Element (H-PCE) architecture is The Hierarchical Path Computation Element (H-PCE) architecture is
defined in RFC 6805. It provides a mechanism to derive an optimum defined in RFC 6805. It provides a mechanism to derive an optimum
end-to-end path in a multi-domain environment by using a hierarchical end-to-end path in a multi-domain environment by using a hierarchical
relationship between domains to select the optimum sequence of relationship between domains to select the optimum sequence of
domains and optimum paths across those domains. domains and optimum paths across those domains.
This document defines extensions to the Path Computation Element This document defines extensions to the Path Computation Element
skipping to change at page 1, line 44 skipping to change at page 1, line 44
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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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
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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 5, 2019. This Internet-Draft will expire on December 2, 2019.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . .1 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 . . . . . . . . . . . . . . . .6 2.1. Path Computation Request . . . . . . . . . . . . . . . .6
2.1.1. Qualification of PCEP Requests . . . . . . . . . . .6 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 Identification . . . . . . . . . . . . . . . .7 2.3. PCE Domain Identification . . . . . . . . . . . . . . . .7
2.4. Domain Diversity . . . . . . . . . . . . . . . . . . . .7 2.4. Domain Diversity . . . . . . . . . . . . . . . . . . . .7
3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . .8 3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . .8
3.1 Applicability to PCC-PCE Communications . . . . . . . . .8 3.1 Applicability to PCC-PCE Communications . . . . . . . . .8
3.2. OPEN Object . . . . . . . . . . . . . . . . . . . . . . .8 3.2. OPEN Object . . . . . . . . . . . . . . . . . . . . . . .8
3.2.1. H-PCE Capability TLV . . . . . . . . . . . . . . . .8 3.2.1. H-PCE Capability TLV . . . . . . . . . . . . . . . .8
3.2.1.1 Backwards Compatibility . . . . . . . . . . . . . . .9 3.2.1.1 Backwards Compatibility . . . . . . . . . . . . . . .9
3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . .10 3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . .10
3.3. RP Object . . . . . . . . . . . . . . . . . . . . . . . .11 3.3. RP Object . . . . . . . . . . . . . . . . . . . . . . . .11
3.3.1. H-PCE-FLAG TLV . . . . . . . . . . . . . . . . . . .11 3.3.1. H-PCE-FLAG TLV . . . . . . . . . . . . . . . . . . .11
3.3.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . .11 3.3.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . .12
3.4. Objective Functions . . . . . . . . . . . . . . . . . . .12 3.4. Objective Functions . . . . . . . . . . . . . . . . . . .12
3.4.1. OF Codes . . . . . . . . . . . . . . . . . . . . . .12 3.4.1. OF Codes . . . . . . . . . . . . . . . . . . . . . .12
3.4.2. OF Object . . . . . . . . . . . . . . . . . . . . . .13 3.4.2. OF Object . . . . . . . . . . . . . . . . . . . . . .13
3.5. Metric Object . . . . . . . . . . . . . . . . . . . . . .14 3.5. Metric Object . . . . . . . . . . . . . . . . . . . . . .14
3.6. SVEC Object . . . . . . . . . . . . . . . . . . . . . . .14 3.6. SVEC Object . . . . . . . . . . . . . . . . . . . . . . .15
3.7. PCEP-ERROR Object . . . . . . . . . . . . . . . . . . . .15 3.7. PCEP-ERROR Object . . . . . . . . . . . . . . . . . . . .15
3.7.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . .15 3.7.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . .15
3.8. NO-PATH Object . . . . . . . . . . . . . . . . . . . . .15 3.8. NO-PATH Object . . . . . . . . . . . . . . . . . . . . .16
4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . .16 4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . .16
4.1. OPEN Procedure between Child PCE and Parent PCE . . . . .16 4.1. OPEN Procedure between Child PCE and Parent PCE . . . . .16
4.2. Procedure to Obtain Domain Sequence . . . . . . . . . . .17 4.2. Procedure to Obtain Domain Sequence . . . . . . . . . . .17
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . .17 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . .17
6. Manageability Considerations . . . . . . . . . . . . . . . .17 6. Manageability Considerations . . . . . . . . . . . . . . . .18
6.1. Control of Function and Policy . . . . . . . . . . . . .18 6.1. Control of Function and Policy . . . . . . . . . . . . .18
6.1.1. Child PCE . . . . . . . . . . . . . . . . . . . . . .18 6.1.1. Child PCE . . . . . . . . . . . . . . . . . . . . . .18
6.1.2. Parent PCE . . . . . . . . . . . . . . . . . . . . .18 6.1.2. Parent PCE . . . . . . . . . . . . . . . . . . . . .
6.1.3. Policy Control . . . . . . . . . . . . . . . . . . .19 6.1.3. Policy Control . . . . . . . . . . . . . . . . . . .19
6.2. Information and Data Models . . . . . . . . . . . . . . .19 6.2. Information and Data Models . . . . . . . . . . . . . . .19
6.3. Liveness Detection and Monitoring . . . . . . . . . . . .19 6.3. Liveness Detection and Monitoring . . . . . . . . . . . .20
6.4. Verify Correct Operations . . . . . . . . . . . . . . . .19 6.4. Verify Correct Operations . . . . . . . . . . . . . . . .20
6.5. Requirements On Other Protocols . . . . . . . . . . . . .20 6.5. Requirements On Other Protocols . . . . . . . . . . . . .20
6.6. Impact On Network Operations . . . . . . . . . . . . . .20 6.6. Impact On Network Operations . . . . . . . . . . . . . .20
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . .20 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . .20
7.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . .20 7.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . .20
7.2. H-PCE-CAPABILITY TLV Flags . . . . . . . . . . . . . . .20 7.2. H-PCE-CAPABILITY TLV Flags . . . . . . . . . . . . . . .21
7.3. Domain-ID TLV Domain type . . . . . . . . . . . . . . . .21 7.3. Domain-ID TLV Domain type . . . . . . . . . . . . . . . .21
7.4. H-PCE-FLAG TLV Flags . . . . . . . . . . . . . . . . . .21 7.4. H-PCE-FLAG TLV Flags . . . . . . . . . . . . . . . . . .22
7.5. OF Codes . . . . . . . . . . . . . . . . . . . . . . . .22 7.5. OF Codes . . . . . . . . . . . . . . . . . . . . . . . .22
7.6. METRIC Types . . . . . . . . . . . . . . . . . . . . . .22 7.6. METRIC Types . . . . . . . . . . . . . . . . . . . . . .22
7.7. New PCEP Error-Types and Values . . . . . . . . . . . . .22 7.7. New PCEP Error-Types and Values . . . . . . . . . . . . .23
7.8. New NO-PATH-VECTOR TLV Bit Flag . . . . . . . . . . . . .23 7.8. New NO-PATH-VECTOR TLV Bit Flag . . . . . . . . . . . . .23
7.9. SVEC Flag . . . . . . . . . . . . . . . . . . . . . . . .23 7.9. SVEC Flag . . . . . . . . . . . . . . . . . . . . . . . .24
7.10. NO-PATH VECTOR TLV Bit Flag. . . . . . . . . . . . . . .23 7.10. NO-PATH VECTOR TLV Bit Flag. . . . . . . . . . . . . . .24
8. Security Considerations . . . . . . . . . . . . . . . . . . .23 8. Security Considerations . . . . . . . . . . . . . . . . . . .24
9. Contributing Authors . . . . . . . . . . . . . . . . . . . . .24 9. Contributing Authors . . . . . . . . . . . . . . . . . . . . .24
10.Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .24 10.Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .25
11. References . . . . . . . . . . . . . . . . . . . . . . . . .24 11. References . . . . . . . . . . . . . . . . . . . . . . . . .25
11.1. Normative References . . . . . . . . . . . . . . . . . .24 11.1. Normative References . . . . . . . . . . . . . . . . . .25
11.2. Informative References . . . . . . . . . . . . . . . . .25 11.2. Informative References . . . . . . . . . . . . . . . . .25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .28
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
A1. Implementation Status . . . . . . . . . . . . . . . . . . .28 A1. Implementation Status . . . . . . . . . . . . . . . . . . .28
A1.1. Inter-layer traffic engineering with H-PCE . . . . . . .28 A1.1. Inter-layer traffic engineering with H-PCE . . . . . . .29
A1.2. Telefonica Netphony (Open Source PCE) . . . . . . . . .30 A1.2. Telefonica Netphony (Open Source PCE) . . . . . . . . .30
A1.3. H-PCE Proof of Concept developed by Huawei . . . . . . .31 A1.3. H-PCE Proof of Concept developed by Huawei . . . . . . .31
1. Introduction 1. Introduction
The Path Computation Element communication Protocol (PCEP) provides The Path Computation Element communication Protocol (PCEP) provides
a mechanism for Path Computation Elements (PCEs) and Path Computation a mechanism for Path Computation Elements (PCEs) and Path Computation
Clients (PCCs) to exchange requests for path computation and Clients (PCCs) to exchange requests for path computation and
responses that provide computed paths. responses that provide computed paths.
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o The child PCEs return the intra-domain paths to the parent PCE; o The child PCEs return the intra-domain paths to the parent PCE;
o The parent PCE constructs the end-to-end inter-domain path based o The parent PCE constructs the end-to-end inter-domain path based
on the intra-domain paths; on the intra-domain paths;
o The parent PCE returns the inter-domain path to the child PCE; o The parent PCE returns the inter-domain path to the child PCE;
o The child PCE forwards the inter-domain path to the PCC. o The child PCE forwards the inter-domain path to the PCC.
The parent PCE may be requested to provide only the sequence of The parent PCE may be requested to provide only the sequence of
domains to achild PCE so that alternative inter-domain path domains to a child PCE so that alternative inter-domain path
computation procedures, including Per Domain (PD) [RFC5152] and computation procedures, including Per Domain (PD) [RFC5152] and
Backwards Recursive Path Computation (BRPC) [RFC5441], may be used. Backwards Recursive Path Computation (BRPC) [RFC5441], may be used.
This document defines the PCEP extensions for the purpose of This document defines the PCEP extensions for the purpose of
implementing Hierarchical PCE procedures, which are described in implementing Hierarchical PCE procedures, which are described in
[RFC6805]. [RFC6805].
1.1. Scope 1.1. Scope
The following functions are out of scope of this document: The following functions are out of scope of this document:
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o Determination of Destination Domain (section 4.5 of [RFC6805]): o Determination of Destination Domain (section 4.5 of [RFC6805]):
* via a collection of reachability information from child domain; * via a collection of reachability information from child domain;
* 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]), suitible mechanisms include: [RFC6805]), although suitable mechanisms include:
* YANG-based management interfaces; * YANG-based management interfaces;
* BGP-LS [RFC7752]; * BGP-LS [RFC7752];
* Future extension to PCEP (such as PCEP-LS). * Future extension to PCEP (such as [I-D.dhodylee-pce-pcep-ls]).
o Learning of Domain connectivity and boundary nodes (BN) addresses. o Learning of Domain connectivity and boundary nodes (BN) addresses,
This could be done achieved: methods to achieve this function include:
* YANG-based management interfaces; * YANG-based management interfaces;
* BGP-LS [RFC7752]; * BGP-LS [RFC7752];
* Future extension to PCEP (such as PCEP-LS). * Future extension to PCEP (such as [I-D.dhodylee-pce-pcep-ls]).
o Stateful PCE Operations. (Refer [I-D.ietf-pce-stateful-hpce]) o Stateful PCE Operations (Refer [I-D.ietf-pce-stateful-hpce])
o The hierarchical relationship model is described in [RFC6805]. It o Applicability of hierarchical PCE to large multi-domain
is applicable to environments with small groups of domains where environments.
visibility from the ingress LSRs is limited. As highlighted in
[RFC7399] applying the hierarchical PCE model to large groups of * The hierarchical relationship model is described in [RFC6805].
domains such as the Internet is not considered feasible or It is applicable to environments with small groups of domains
desirable. where visibility from the ingress LSRs is limited. As highlighted
in [RFC7399] applying the hierarchical PCE model to very large
groups of domains, such as the Internet, is not considered
feasible or desirable.
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
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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 simultaneously. The is possible for a PCE to manage multiple domains simultaneously. The
PCE domain could 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 is domain-diverse if they do not [RFC6805] and described as "A pair of paths are domain-diverse if
traverse any of the same transit domains. Domain diversity may be they do not transit any of the same domains. A pair of paths that
maximized for a pair of paths by selecting paths that have the share a common ingress and egress are domain-diverse if they only
smallest number of shared domains. Path computation should share the same domains at the ingress and egress (the ingress and
facilitate the selection of domain diverse paths as a way to reduce egress domains). Domain diversity may be maximized for a pair of
the risk of shared failure and automatically helps to ensure path paths by selecting paths that have the smallest number of shared
diversity for a pair of LSPs. domains."
The main motivation behind domain diversity is to avoid fate sharing, The main motivation behind domain diversity is to avoid fate sharing,
but it can also be because of some geo-political reasons and but it can also be because of some geo-political reasons and
commercial relationships that would require domain diversity. For commercial relationships that would require domain diversity. For
example, a pair of paths should choose different transit Autonomous example, a pair of paths should choose different transit Autonomous
System (AS) because of some policy considerations. System (AS) because of some policy considerations.
In the case when full domain diversity could not be achieved, it is In the case when full domain diversity could not be achieved, it is
helpful to minimize the commonly shared domains. Also, it is helpful to minimize the commonly shared domains. Also, it is
interesting to note that other scope of diversity (node, link, SRLG interesting to note that other scope of diversity (node, link, SRLG
etc.) can still be applied inside the commonly shared domains. etc.) can still be applied inside the commonly shared domains.
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Thus, the information that may be encoded in a PCReq can be sent Thus, the information that may be encoded in a PCReq can be sent
from a PCC towards the child PCE. This includes the RP object from a PCC towards the child PCE. This includes the RP object
(Section 3.3) and the Objective Function (OF) codes and objects (Section 3.3) and the Objective Function (OF) codes and objects
(Section 3.4). A PCC and a child PCE could also exchange the (Section 3.4). A PCC and a child PCE could also exchange the
capability (Section 3.2.1) during its session. capability (Section 3.2.1) during its session.
This allows a PCC to request paths that transit multiple This allows a PCC to request paths that transit multiple
domains utilizing the capabilities defined in this document. domains utilizing the capabilities defined in this document.
3.2. OPEN Object 3.2. OPEN Object
Two new TLVs are defined in this document to be carried within an Two new TLVs are defined in this document to be carried within an
OPEN object. This way, during the PCEP session establishment, the OPEN object. This way, during the PCEP session establishment, the
H-PCE capability and Domain information can be advertised. H-PCE capability and Domain information can be advertised.
3.2.1. H-PCE Capability TLV 3.2.1. 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.
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Unassigned bits MUST be set to 0 on transmission and MUST be ignored Unassigned bits MUST be set to 0 on transmission and MUST be ignored
on receipt. on receipt.
The inclusion of this TLV in an OPEN object indicates that the H-PCE The inclusion of this TLV in an OPEN object indicates that the H-PCE
extensions are supported by the PCEP speaker. The child PCE MUST extensions are supported by the PCEP speaker. The child PCE MUST
include this TLV and set the P flag. The parent PCE MUST include include this TLV and set the P flag. The parent PCE MUST include
this TLV and unset the P flag. this TLV and unset the P flag.
The setting of the P flag (parent PCE request bit) would mean that The setting of the P flag (parent PCE request bit) would mean that
the PCEP speaker wants the peer to be a parent PCE, so in the case the PCEP speaker wants the peer to be a parent PCE, so in the case
of a PCC to Child-PCE relationship, neither entity would set the P of a PCC to Child-PCE relationship, neither entity would set the P
flag. flag.
If both peers attempt to set the P flag then the session If both peers attempt to set the P flag then the session
establishment MUST fail, and the PCEP speaker MUST respond with PCErr establishment MUST fail, and the PCEP speaker MUST respond with PCErr
message using Error-Type 1: "PCEP Session Establishment Failure" as message using Error-Type 1: "PCEP Session Establishment Failure" as
per [RFC5440]. per [RFC5440].
If the PCE understands the H-PCE path computation request but did not If the PCE understands the H-PCE path computation request but did not
advertise its H-PCE capability, it MUST send a PCErr message with advertise its H-PCE capability, it MUST send a PCErr message with
Error-Type=TBD8 ("H-PCE error") and Error-Value=1 ("Parent PCE Error-Type=TBD8 ("H-PCE error") and Error-Value=1 ("H-PCE Capability
Capability not advertised"). not advertised").
3.2.1.1 Backwards Compatibility 3.2.1.1 Backwards Compatibility
Section 7.1 of [RFC5440] requires that "Unrecognized TLVs MUST be Section 7.1 of [RFC5440] requires that "Unrecognized TLVs MUST be
ignored. ignored.
That means that a PCE that does not support this document but that That means that a PCE that does not support this document but that
receives an Open Message containing an Open Object that includes receives an Open Message containing an Open Object that includes
an H-PCE-CAPABILITIES TLV will ignore that TLV and will continue to an H-PCE-CAPABILITIES TLV will ignore that TLV and will continue to
attempt to establish a PCEP session. It will, however, not include attempt to establish a PCEP session. It will, however, not include
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| 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:
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 zeros 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 a 4-byte OSPF area ID. * Type=3: the Domain ID field carries a 4-byte OSPF area ID.
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computed path does not enter a domain more than once. computed path does not enter a domain more than once.
Unassigned bits MUST be set to 0 on transmission and MUST be ignored Unassigned bits MUST be set to 0 on transmission and MUST be ignored
on receipt. on receipt.
The presence of the TLV indicates that the H-PCE based path The presence of the TLV indicates that the H-PCE based path
computation is requested as per this document. computation is requested as per this document.
3.3.2. Domain-ID TLV 3.3.2. Domain-ID TLV
The usage of Domain-ID TLV, carried in an OPEN object, is used to The Domain-ID TLV, carried in an OPEN object, is used to indicate a
indicate a (list of) managed domains and is described in (list of) managed domains and is described in Section 3.3.1. This
Section 3.3.1. This TLV, when carried in an RP object, indicates the TLV, when carried in an RP object, indicates the destination domain
destination domain ID. If a PCC knows the egress domain, it can ID. If a PCC knows the egress domain, it can supply this information
supply this information in the PCReq message. The format and in the PCReq message. The format and procedure of this TLV are
procedure of this TLV are defined in Section 3.2.2. defined in Section 3.2.2.
If a Domain-id TLV is used in the RP object, and the destination is If a Domain-id TLV is used in the RP object, and the destination is
not actually in the indicated domain, then the parent not actually in the indicated domain, then the parent
PCE should respond with a NO-PATH object and NO-PATH VECTOR TLV PCE should respond with a NO-PATH object and NO-PATH VECTOR TLV
should be used. A new bit number is assigned to indicate should be used. A new bit number is assigned to indicate
"Destination not found in the indicated domain" (see Section 3.7). "Destination not found in the indicated domain" (see Section 3.7).
3.4. Objective Functions 3.4. Objective Functions
3.4.1. OF Codes 3.4.1. OF Codes
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3.6. SVEC Object 3.6. 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
and SRLG diverse). This document defines a new flag O for domain and SRLG diverse). This document defines a new flag O for domain
diversity. diversity.
The following new bit is added to the Flags field: The following new bit is added to the Flags field:
o O (Domain diverse) bit - TBD14 : when set, this indicates that the o Domain Diverse O-bit - TBD14 : 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 domains in following RP objects MUST NOT have any transit domains 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.) MAY be set and domains. The other bit in SVEC object (N, L, S etc.) MAY be set and
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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 child PCE sends a PCReq to a peer PCE, which requires parental When a child PCE sends a PCReq to a peer PCE, which requires parental
activity and H-PCE capability flags TLV but which were not included activity and H-PCE capability flags TLV but which were not included
in the session establishment procedure described above, the peer PCE in the session establishment procedure described above, the peer PCE
should send a PCErr message to the child PCE and should specify the SHOULD send a PCErr message to the child PCE and MUST specify the
error-type=TBD8 (H-PCE error) and error-value=1 (H-PCE capability was error-type=TBD8 (H-PCE error) and error-value=1 (H-PCE capability was
not advertised) in the PCEP-ERROR object. not advertised) in the PCEP-ERROR object.
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 the peer PCE does not want to act as the parent parental activity and the peer PCE does not want to act as the parent
for it, the peer PCE should send a PCErr message to the child PCE and for it, the peer PCE SHOULD send a PCErr message to the child PCE and
specify the error-type=TBD8 (H-PCE error) and error-value=2 (Parent MUST specify the error-type=TBD8 (H-PCE error) and error-value=2
PCE capability cannot be provided) in the PCEP-ERROR object. (Parent PCE capability cannot be provided) in the PCEP-ERROR object.
4.2. Procedure to Obtain Domain Sequence 4.2. Procedure to Obtain Domain Sequence
If a child PCE only wants to get the domain sequence for a multi- If a child PCE only wants to get the domain sequence for a multi-
domain path computation from a parent PCE, it can set the Domain Path domain path computation from a parent PCE, it can set the Domain Path
Request bit in the H-PCE-FLAG TLV in the RP object carried in a PCReq Request bit in the H-PCE-FLAG TLV in the RP object carried in a PCReq
message. The parent PCE which receives the PCReq message tries to message. The parent PCE which receives the PCReq message tries to
compute a domain sequence for it (instead of the E2E path). If the compute a domain sequence for it (instead of the E2E path). If the
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 Explicit Route Object (ERO) which carries the domain sequence in the Explicit Route Object (ERO)
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6.1.1. Child PCE 6.1.1. Child PCE
Support of the hierarchical procedure will be controlled by the Support of the hierarchical procedure will be controlled by the
management organization responsible for each child PCE. A child PCE management organization responsible for each child PCE. A child PCE
must be configured with the address of its parent PCE in order for it must be configured with the address of its parent PCE in order for it
to interact with its parent PCE. The child PCE must also be to interact with its parent PCE. The child PCE must also be
authorized to peer with the parent PCE. authorized to peer with the parent PCE.
6.1.2. Parent PCE 6.1.2. Parent PCE
The parent PCE must only accept path computation requests from The parent PCE MUST only accept path computation requests from
authorized child PCEs. If a parent PCE receives requests from an authorized child PCEs. If a parent PCE receives requests from an
unauthorized child PCE, the request should be dropped. This means unauthorized child PCE, the request SHOULD be dropped. This means
that a parent PCE must be configured with the identities and security that a parent PCE MUST be able to cryptographically authenticate
credentials of all of its child PCEs, or there must be some form of requests from child PCEs.
shared secret that allows an unknown child PCE to be authorized by
the parent PCE. Multi-party shared key authentication schemes are not recommended for
inter-domain relationships because of the potential for impersonation
and repudiation and for the operational difficulties should
revocation be required.
The choice of authentication schemes to employ may be left to
implementers of H-PCE and are not discussed further in this document.
6.1.3. Policy Control 6.1.3. Policy Control
It may be necessary to maintain a policy module on the parent PCE It may be necessary to maintain a policy module on the parent PCE
[RFC5394]. This would allow the parent PCE to apply commercially [RFC5394]. This would allow the parent PCE to apply commercially
relevant constraints such as SLAs, security, peering preferences, and relevant constraints such as SLAs, security, peering preferences, and
monetary costs. monetary costs.
It may also be necessary for the parent PCE to limit the It may also be necessary for the parent PCE to limit the
end-to-end path selection by including or excluding specific domains end-to-end path selection by including or excluding specific domains
based on commercial relationships, security implications, and based on commercial relationships, security implications, and
reliability. reliability.
6.2. Information and Data Models 6.2. Information and Data Models
A MIB module for PCEP was published as RFC 7420 [RFC7420] that A MIB module for PCEP was published as RFC 7420 [RFC7420] that
describes managed objects for modelling of PCEP communication. A describes managed objects for modelling of PCEP communication. A
YANG module for PCEP has also been proposed [I-D.ietf-pce-pcep-yang]. YANG module for PCEP has also been proposed [I-D.ietf-pce-pcep-yang].
Aditionally, H-PCE MIB module, or additional data model, will be Additionally, H-PCE MIB module, or additional data model, will be
required to report parent PCE and child PCE information, including: required to report parent PCE and child PCE information, including:
o parent PCE configuration and status, o parent PCE configuration and status,
o child PCE configuration and information, o child PCE configuration and information,
o notifications to indicate session changes between parent PCEs and o notifications to indicate session changes between parent PCEs and
child PCEs, and child PCEs, and
o notification of parent PCE TED updates and changes. o notification of parent PCE TED updates and changes.
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Value Meaning Value Meaning
----------------------------------------------- -----------------------------------------------
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-FLAG
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 RP object. New values are to be assigned PCE-FLAGS TLV of the PCEP RP object. New values are to be assigned
by Standards Action [RFC8126]. Each bit should be tracked with the by Standards Action [RFC8126]. Each bit should be 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
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in the indicated domain. in the indicated domain.
7.9. SVEC Flag 7.9. SVEC Flag
IANA maintains a sub-registry "SVEC Object Flag Field" of bit flags IANA maintains a sub-registry "SVEC Object Flag Field" of bit flags
carried in the PCEP SVEC object as defined in [RFC5440]. IANA is carried in the PCEP SVEC object as defined in [RFC5440]. IANA is
requested to assign one new bit flag as follows: requested to assign one new bit flag as follows:
Bit Number Name Flag Reference Bit Number Name Flag Reference
------------------------------------------------------ ------------------------------------------------------
TBD14 Domain Diverse This I.D. TBD14 Domain Diverse O-bit This I.D.
8. Security Considerations 8. Security Considerations
The hierarchical PCE procedure relies on PCEP and inherits the The hierarchical PCE procedure relies on PCEP and inherits the
security requirements defined in [RFC5440]. As PCEP operates over security considerations defined in [RFC5440]. As PCEP operates over
TCP, it may also make use of TCP security mechanisms, such as TCP TCP, it may also make use of TCP security mechanisms, such as TCP
Authentication Option (TCP-AO) [RFC5925] or Transport Layer Authentication Option (TCP-AO) [RFC5925] or Transport Layer
Security (TLS) [RFC8253]. Security (TLS) [RFC8253].
Any multi-domain operation necessarily involves the exchange of Any multi-domain operation necessarily involves the exchange of
information across domain boundaries. This may represent a information across domain boundaries. This may represent a
significant security and confidentiality risk especially when the significant security and confidentiality risk especially when the
child domains are controlled by different commercial concerns. PCEP child domains are controlled by different commercial concerns. PCEP
allows individual PCEs to maintain the confidentiality of their allows individual PCEs to maintain the confidentiality of their
domain path information using path-keys [RFC5520], and the H-PCE domain path information using path-keys [RFC5520], and the H-PCE
skipping to change at page 24, line 37 skipping to change at page 25, line 7
Dhruv Dhody Dhruv Dhody
Huawei Technologies Huawei Technologies
Divyashree Techno Park, Whitefield Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066 Bangalore, Karnataka 560066
India India
EMail: dhruv.ietf@gmail.com EMail: dhruv.ietf@gmail.com
10.Acknowledgements 10.Acknowledgements
The authors would like to thank Mike McBride for his detailed review, The authors would like to thank Mike McBride, Kyle Rose, Roni Even
comments and suggestions which helped improve this document. for their detailed review, comments and suggestions which helped
improve this document.
11. References 11. References
11.1. Normative References 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 27, line 21 skipping to change at page 27, line 38
[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-09 (work in progress), October 2018. yang-11 (work in progress), March 2019.
[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-06 (work in Element (PCE).", draft-ietf-pce-stateful-hpce-07 (work in
progress), June 2018. progress), April 2019.
[I-D.dhodylee-pce-pcep-ls]
Dhody, D., Lee, Y., and D. Ceccarelli, "PCEP Extension for
Distribution of Link-State and TE Information.", draft-
dhodylee-pce-pcep-ls-13 (work in progress), February 2019.
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
Quintin Zhao Quintin Zhao
Huawei Huawei
125 Nagog Technology Park 125 Nagog Technology Park
Acton, MA 01719 Acton, MA 01719
USA USA
EMail: quintin.zhao@huawei.com EMail: quintin.zhao@huawei.com
Oscar Gonzalez de Dios Oscar Gonzalez de Dios
Telefonica I+D Telefonica
Don Ramon de la Cruz 82-84 Don Ramon de la Cruz 82-84
Madrid 28045 Madrid 28045
Spain Spain
EMail: ogondio@tid.es EMail: oscar.gonzalezdedios@telefonica.com
Ramon Casellas Ramon Casellas
CTTC CTTC
Av. Carl Friedrich Gauss n.7 Av. Carl Friedrich Gauss n.7
Barcelona, Castelldefels Barcelona, Castelldefels
Spain Spain
EMail: ramon.casellas@cttc.es EMail: ramon.casellas@cttc.es
Daniel King Daniel King
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