draft-ietf-pce-lsp-control-request-09.txt   draft-ietf-pce-lsp-control-request-10.txt 
PCE Working Group A. Raghuram PCE Working Group A. Raghuram
Internet-Draft A. Goddard Internet-Draft A. Goddard
Intended status: Standards Track AT&T Intended status: Standards Track AT&T
Expires: March 16, 2020 J. Karthik Expires: April 15, 2020 J. Karthik
S. Sivabalan S. Sivabalan
Cisco Systems, Inc. Cisco Systems, Inc.
M. Negi M. Negi
Huawei Technologies Huawei Technologies
September 13, 2019 October 13, 2019
Ability for a Stateful Path Computation Element (PCE) to request and Ability for a Stateful Path Computation Element (PCE) to request and
obtain control of a Label Switched Path (LSP) obtain control of a Label Switched Path (LSP)
draft-ietf-pce-lsp-control-request-09 draft-ietf-pce-lsp-control-request-10
Abstract Abstract
A Stateful Path Computation Element (PCE) retains information about A Stateful Path Computation Element (PCE) retains information about
the placement of Multiprotocol Label Switching (MPLS) Traffic the placement of Multiprotocol Label Switching (MPLS) Traffic
Engineering Label Switched Paths (TE LSPs). When a PCE has stateful Engineering Label Switched Paths (TE LSPs). When a PCE has stateful
control over LSPs it may send indications to LSP head-ends to modify control over LSPs it may send indications to LSP head-ends to modify
the attributes (especially the paths) of the LSPs. A Path the attributes (especially the paths) of the LSPs. A Path
Computation Client (PCC) has set up LSPs under local configuration Computation Client (PCC) that has set up LSPs under local
may delegate control of those LSPs to a stateful PCE. configuration may delegate control of those LSPs to a stateful PCE.
There are use-cases in which a stateful PCE may wish to obtain There are use-cases in which a stateful PCE may wish to obtain
control of locally configured LSPs of which it is aware but that have control of locally configured LSPs of which it is aware but that have
not been delegated to the PCE. not been delegated to the PCE.
This document describes an extension to the Path Computation Element This document describes an extension to the Path Computation Element
communication Protocol (PCEP) to enable a PCE to make such requests. communication Protocol (PCEP) to enable a PCE to make requests for
such control.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
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 April 15, 2020.
This Internet-Draft will expire on March 16, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. LSP Control Request Flag . . . . . . . . . . . . . . . . . . 4 3. LSP Control Request Flag . . . . . . . . . . . . . . . . . . 4
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 6 5. Implementation Status . . . . . . . . . . . . . . . . . . . . 6
5.1. Huawei's Proof of Concept based on ONOS . . . . . . . . . 6 5.1. Huawei's Proof of Concept based on ONOS . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7.1. SRP Object Flags . . . . . . . . . . . . . . . . . . . . 7 7.1. SRP Object Flags . . . . . . . . . . . . . . . . . . . . 7
8. Manageability Considerations . . . . . . . . . . . . . . . . 7 8. Manageability Considerations . . . . . . . . . . . . . . . . 8
8.1. Control of Function and Policy . . . . . . . . . . . . . 8 8.1. Control of Function and Policy . . . . . . . . . . . . . 8
8.2. Information and Data Models . . . . . . . . . . . . . . . 8 8.2. Information and Data Models . . . . . . . . . . . . . . . 8
8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 8 8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 8
8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 8 8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 8
8.5. Requirements On Other Protocols . . . . . . . . . . . . . 8 8.5. Requirements On Other Protocols . . . . . . . . . . . . . 8
8.6. Impact On Network Operations . . . . . . . . . . . . . . 8 8.6. Impact On Network Operations . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9 10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 9 10.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 11 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
Stateful Path Computation Element (PCE) communication Protocol (PCEP) Stateful Path Computation Element (PCE) communication Protocol (PCEP)
extensions [RFC8231] specifies a set of extensions to PCEP [RFC5440] extensions [RFC8231] specifies a set of extensions to PCEP [RFC5440]
to enable stateful control of Traffic Engineering Label Switched to enable stateful control of Traffic Engineering Label Switched
Paths (TE LSPs) between and across PCEP sessions in compliance with Paths (TE LSPs) between and across PCEP sessions in compliance with
[RFC4657]. It includes mechanisms to effect LSP state [RFC4657]. It includes mechanisms to effect LSP state
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to the PCE in the delegation operation. to the PCE in the delegation operation.
For Redundant Stateful PCEs (section 5.7.4. of [RFC8231]), during a For Redundant Stateful PCEs (section 5.7.4. of [RFC8231]), during a
PCE failure, one of the redundant PCE could request to take control PCE failure, one of the redundant PCE could request to take control
over an LSP. The redundant PCEs may use a local policy or a over an LSP. The redundant PCEs may use a local policy or a
proprietary election mechanism to decide which PCE would take proprietary election mechanism to decide which PCE would take
control. In this case, a mechanism is needed for a stateful PCE to control. In this case, a mechanism is needed for a stateful PCE to
request control of one or more LSPs from a PCC, so that a newly request control of one or more LSPs from a PCC, so that a newly
elected primary PCE can request to take over control. elected primary PCE can request to take over control.
In case of virtualized PCEs (vPCE) running as virtual network In case of virtualized PCEs (vPCE) running in virtual network
function (VNF), as the computation load in the network increases, a function (VNF) mode, as the computation load in the network
new instance of vPCE could be instantiated to balance the current increases, a new instance of vPCE could be instantiated to balance
load. The PCEs could use proprietary algorithm to decide which LSPs the current load. The PCEs could use a proprietary algorithm to
to be assigned to the new vPCE. Thus having a mechanism for the PCE decide which LSPs to be assigned to the new vPCE. Thus, having a
to request control of some LSPs is needed. mechanism for the PCE to request control of some LSPs is needed.
In some deployments, the operator would like to use stateful PCE for In some deployments, the operator would like to use stateful PCE for
global optimization algorithms but would still like to keep the global optimization algorithms but would still like to keep the
control of the LSP at the PCC. In such cases, a stateful PCE could control of the LSP at the PCC. In such cases, a stateful PCE could
request to take control during the global optimization and return the request to take control during the global optimization and return the
delegation once done. delegation once done.
Note that [RFC8231] specifies a mechanism for a PCC to delegate an Note that [RFC8231] specifies a mechanism for a PCC to delegate an
orphaned LSP to another PCE. The mechanism defined in this document orphaned LSP to another PCE. The mechanism defined in this document
can be used in conjunction to [RFC8231]. Ultimately, it is the PCC can be used in conjunction to [RFC8231]. Ultimately, it is the PCC
that decides which PCE to delegate the orphaned LSP. that decides which PCE to delegate the orphaned LSP to.
This specification provides a simple extension, by using this a PCE This specification provides a simple extension: by using it a PCE can
can request control of one or more LSPs from any PCC over the request control of one or more LSPs from any PCC over the stateful
stateful PCEP session. The procedures for granting and relinquishing PCEP session. The procedures for granting and relinquishing control
control of the LSPs are specified in accordance with the of the LSPs are specified in accordance with the specification
specification [RFC8231]. [RFC8231] unless explicitly set aside in this document.
2. Terminology 2. Terminology
This document uses the following terms defined in [RFC5440]: This document uses the following terms defined in [RFC5440]:
PCC: Path Computation Client. PCC: Path Computation Client.
PCE: Path Computation Element. PCE: Path Computation Element.
PCEP: Path Computation Element communication Protocol. PCEP: Path Computation Element communication Protocol.
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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
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. LSP Control Request Flag 3. LSP Control Request Flag
The Stateful PCE Request Parameters (SRP) object is defined in The Stateful PCE Request Parameters (SRP) object is defined in
Section 7.2 of [RFC8231], it includes a Flags field. Section 7.2 of [RFC8231] and it includes a Flags field.
A new flag, the "LSP-Control Request Flag" (C), is introduced in the A new flag, the "LSP-Control Request Flag" (C) - TBD, is introduced
SRP object. On a PCUpd message, a PCE sets the C Flag to 1 to in the SRP object. On a PCUpd message, a PCE sets the C Flag to 1 to
indicate that it wishes to gain control of LSPs. The LSPs are indicate that it wishes to gain control of LSPs. The LSPs are
identified by the LSP object. A PLSP-ID of value other than 0 and identified by the LSP object. A PLSP-ID of value other than 0 and
0xFFFFF is used to identify the LSP for which the PCE requests 0xFFFFF is used to identify the LSP for which the PCE requests
control. The PLSP-ID value of 0 indicates that the PCE is requesting control. The PLSP-ID value of 0 indicates that the PCE is requesting
control of all LSPs originating from the PCC that it wishes to control of all LSPs originating from the PCC that it wishes to
delegate. The C Flag has no meaning in other PCEP messages that delegate. The C Flag has no meaning in other PCEP messages that
carry SRP object and the flag MUST be set to 0 on transmission and carry an SRP object and the flag MUST be set to 0 on transmission and
MUST be ignored on receipt. MUST be ignored on receipt.
4. Operation 4. Operation
During normal operation, a PCC that wishes to delegate the control of During normal operation, a PCC that wishes to delegate the control of
an LSP sets the D Flag (delegate, Section 7.3 of [RFC8231]) to 1 in an LSP sets the D Flag (delegate, Section 7.3 of [RFC8231]) to 1 in
all PCRpt messages pertaining to the LSP. The PCE confirms the all PCRpt messages pertaining to the LSP. The PCE confirms the
delegation by setting D Flag to 1 in all PCUpd messages pertaining to delegation by setting D Flag to 1 in all PCUpd messages pertaining to
the LSP. The PCC revokes the control of the LSP from the PCE by the LSP. The PCC revokes the control of the LSP from the PCE by
setting D Flag to 0 in PCRpt messages pertaining to the LSP. If the setting D Flag to 0 in PCRpt messages pertaining to the LSP. If the
PCE wishes to relinquish the control of the LSP, it sets D Flag to 0 PCE wishes to relinquish the control of the LSP, it sets D Flag to 0
in all PCUpd messages pertaining to the LSP. in all PCUpd messages pertaining to the LSP.
If a PCE wishes to gain control over an LSP, it sends a PCUpd message If a PCE wishes to gain control over an LSP, it sends a PCUpd message
with C Flag set to 1 in SRP object. The LSP for which the PCE with C Flag set to 1 in SRP object. The LSP for which the PCE
requests control is identified by the PLSP-ID. The PLSP-ID of 0 requests control is identified by the PLSP-ID. The PLSP-ID of 0
indicates that the PCE wants control over all LSPs originating from indicates that the PCE wants control over all LSPs originating from
the PCC. A PCC that receives a PCUpd message with C Flag set to 1 the PCC. A PCC that receives a PCUpd message with C Flag set to 1
and PLSP-ID of 0 MUST NOT trigger the error condition for unknown and PLSP-ID of 0 MUST NOT trigger the error condition for unknown
PLSP-ID in an LSP update request as per [RFC8231]. The D Flag and C PLSP-ID in an LSP update request as per [RFC8231]. The D Flag and C
Flag are mutually exclusive in PCUpd message. The PCE SHOULD NOT Flag are mutually exclusive in a PCUpd message. The PCE SHOULD NOT
send control request for LSP which is already delegated to the PCE, send a control request for the LSP which is already delegated to the
i.e. if the D Flag is set in the PCUpd message, then C Flag SHOULD PCE, i.e. if the D Flag is set in the PCUpd message, then the C Flag
NOT be set. If a PCC receives a PCUpd message with D Flag set in the SHOULD NOT be set. If a PCC receives a PCUpd message with D Flag set
LSP object (i.e. LSP is already delegated) and the C Flag is also in the LSP object (i.e. LSP is already delegated) and the C Flag is
set (i.e. PCE is making a control request), the PCC MUST ignore the also set (i.e. PCE is making a control request), the PCC MUST ignore
C Flag. A PCC can decide to delegate the control of the LSP at its the C Flag. A PCC can decide to delegate the control of the LSP at
own discretion. If the PCC grants or denies the control, it sends a its own discretion. If the PCC grants or denies the control, it
PCRpt message with D Flag set to 1 and 0 respectively in accordance sends a PCRpt message with D Flag set to 1 and 0 respectively in
with stateful PCEP [RFC8231]. If the PCC does not grant the control, accordance with stateful PCEP [RFC8231]. If the PCC does not grant
it MAY choose to not respond, and the PCE MAY choose to retry the control, it MAY choose to not respond, and the PCE MAY choose to
requesting the control preferably using exponentially increasing retry requesting the control preferably using exponentially
timer. A PCE ignores the C Flag on the PCRpt message. Note that, if increasing timer. A PCE ignores the C Flag on the PCRpt message.
the PCUpd message with C Flag set is received for a currently non- Note that, if the PCUpd message with C Flag set is received for a
delegated LSP (for which the PCE is requesting delegation), this MUST currently non-delegated LSP (for which the PCE is requesting
NOT trigger the error handling as specified in [RFC8231] (a PCErr delegation), this MUST NOT trigger the error handling as specified in
with Error-type=19 (Invalid Operation) and error-value 1 (Attempted [RFC8231] (a PCErr with Error-type=19 (Invalid Operation) and error-
LSP Update Request for a non-delegated LSP)). value 1 (Attempted LSP Update Request for a non-delegated LSP)).
As per [RFC8231], a PCC cannot delegate an LSP to more than one PCE As per [RFC8231], a PCC cannot delegate an LSP to more than one PCE
at any time. If a PCE requests control of an LSP that has already at any time. If a PCE requests control of an LSP that has already
been delegated by the PCC to another PCE, the PCC MAY ignore the been delegated by the PCC to another PCE, the PCC MAY ignore the
request, or MAY revoke the delegation to the first PCE before request, or MAY revoke the delegation to the first PCE before
delegating it to the second. This choice is a matter of local delegating it to the second. This choice is a matter of local
policy. policy.
It should be noted that a legacy implementation of PCC, that does not It should be noted that a legacy implementation of PCC that does not
support this extension would trigger the error condition as specified support this extension would trigger the error condition as specified
in [RFC8231] (a PCErr with Error-type=19 (Invalid Operation) and in [RFC8231] (a PCErr with Error-type=19 (Invalid Operation) and
error-value 1 (Attempted LSP Update Request for a non-delegated LSP)) error-value 1 (Attempted LSP Update Request for a non-delegated
as the D Flag would be unset in this update request. Further, in LSP)), as the D Flag would be unset in this update request. Further,
case of PLSP-ID of 0, the error condition as specified in [RFC8231] in case of PLSP-ID of 0, the error condition as specified in
(a PCErr with Error-type=19 (Invalid Operation) and error-value 3 [RFC8231] (a PCErr with Error-type=19 (Invalid Operation) and error-
(Attempted LSP Update Request for an LSP identified by an unknown value 3 (Attempted LSP Update Request for an LSP identified by an
PSP-ID)) would be triggered. unknown PSP-ID)) would be triggered.
[RFC8281] describes the setup, maintenance and teardown of PCE- [RFC8281] describes the setup, maintenance and teardown of PCE-
initiated LSPs under the stateful PCE model. It also specifies how a initiated LSPs under the stateful PCE model. It also specifies how a
PCE MAY obtain control over an orphaned LSP that was PCE-initiated. PCE may obtain control over an orphaned LSP that was PCE-initiated.
A PCE implementation can apply the mechanism described in this A PCE implementation can apply the mechanism described in this
document in conjunction with those in [RFC8281]. document in conjunction with those in [RFC8281].
5. Implementation Status 5. Implementation Status
[Note to the RFC Editor - remove this section before publication, as [Note to the RFC Editor - remove this section before publication, as
well as remove the reference to RFC 7942.] well as remove the reference to RFC 7942.]
This section records the status of known implementations of the This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this protocol defined by this specification at the time of posting of this
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The security considerations listed in [RFC8231] and [RFC8281] apply The security considerations listed in [RFC8231] and [RFC8281] apply
to this document as well. However, this document also introduces a to this document as well. However, this document also introduces a
new attack vector. An attacker may flood the PCC with request to new attack vector. An attacker may flood the PCC with request to
delegate all of its LSPs at a rate which exceeds the PCC's ability to delegate all of its LSPs at a rate which exceeds the PCC's ability to
process them, either by spoofing messages or by compromising the PCE process them, either by spoofing messages or by compromising the PCE
itself. The PCC SHOULD be configured with a threshold rate for the itself. The PCC SHOULD be configured with a threshold rate for the
delegation requests received from the PCE. If the threshold is delegation requests received from the PCE. If the threshold is
reached, it is RECOMMENDED to log the issue. reached, it is RECOMMENDED to log the issue.
A PCC is the ultimate arbiter of delegation. As per [RFC8231], a
local policy at PCC is used to influence the delegation. A PCC can
also revoke the delegation at any time. A PCC MUST NOT blindly trust
the control requests and SHOULD take local policy and other factors
into consideration before honoring the request.
As per [RFC8231], it is RECOMMENDED that these PCEP extensions only As per [RFC8231], it is RECOMMENDED that these PCEP extensions only
be activated on authenticated and encrypted sessions across PCEs and be activated on authenticated and encrypted sessions across PCEs and
PCCs belonging to the same administrative authority, using Transport PCCs belonging to the same administrative authority, using Transport
Layer Security (TLS) [RFC8253], as per the recommendations and best Layer Security (TLS) [RFC8253], as per the recommendations and best
current practices in [RFC7525] (unless explicitly excluded in current practices in [RFC7525] (unless explicitly excluded in
[RFC8253]). [RFC8253]).
7. IANA Considerations 7. IANA Considerations
7.1. SRP Object Flags 7.1. SRP Object Flags
IANA maintains a registry called the "Path Computation Element IANA maintains a registry called the "Path Computation Element
Protocol (PCEP) Numbers" registry. It contains a subregistry called Protocol (PCEP) Numbers" registry. It contains a subregistry called
the "SRP Object Flag Field" registry. This document requests IANA to the "SRP Object Flag Field" registry. This document requests IANA to
allocate following code point in the "SRP Object Flag Field" allocate following code point in the "SRP Object Flag Field"
subregistry. subregistry.
Bit Description Reference Bit Description Reference
TBD LSP-Control This document TBD LSP-Control Request Flag This document
8. Manageability Considerations 8. Manageability Considerations
All manageability requirements and considerations listed in [RFC5440] All manageability requirements and considerations listed in [RFC5440]
and [RFC8231] apply to PCEP protocol extensions defined in this and [RFC8231] apply to PCEP protocol extensions defined in this
document. In addition, requirements and considerations listed in document. In addition, requirements and considerations listed in
this section apply. this section apply.
8.1. Control of Function and Policy 8.1. Control of Function and Policy
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Thanks to Jonathan Hardwick to remind the authors to not use Thanks to Jonathan Hardwick to remind the authors to not use
suggested values in IANA section. suggested values in IANA section.
Thanks to Adrian Farrel, Haomian Zheng and Tomonori Takeda for their Thanks to Adrian Farrel, Haomian Zheng and Tomonori Takeda for their
valuable comments. valuable comments.
Thanks to Shawn M. Emery for security directorate's review. Thanks to Shawn M. Emery for security directorate's review.
Thanks to Francesca Palombini for GENART review. Thanks to Francesca Palombini for GENART review.
Thanks to Martin Vigoureux, Alvaro Retana, and Barry Leiba for IESG
reviews.
10. References 10. References
10.1. Normative References 10.1. 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>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
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