draft-ietf-pce-lsp-control-request-05.txt   draft-ietf-pce-lsp-control-request-06.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: December 23, 2019 J. Karthik Expires: December 27, 2019 J. Karthik
S. Sivabalan S. Sivabalan
Cisco Systems, Inc. Cisco Systems, Inc.
M. Negi M. Negi
Huawei Technologies Huawei Technologies
June 21, 2019 June 25, 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-05 draft-ietf-pce-lsp-control-request-06
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) has set up LSPs under local configuration
may delegate control of those LSPs to a stateful PCE. 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.
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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 December 23, 2019. This Internet-Draft will expire on December 27, 2019.
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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7.1. SRP Object Flags . . . . . . . . . . . . . . . . . . . . 7 7.1. SRP Object Flags . . . . . . . . . . . . . . . . . . . . 7
8. Manageability Considerations . . . . . . . . . . . . . . . . 7 8. Manageability Considerations . . . . . . . . . . . . . . . . 7
8.1. Control of Function and Policy . . . . . . . . . . . . . 7 8.1. Control of Function and Policy . . . . . . . . . . . . . 7
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 . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 9 10.2. Informative References . . . . . . . . . . . . . . . . . 9
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
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The Stateful PCE Request Parameters (SRP) object is defined in The Stateful PCE Request Parameters (SRP) object is defined in
[RFC8231], it includes a Flags field. [RFC8231], 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), is introduced in the
SRP object. On a PCUpd message, a PCE sets the C Flag to 1 to 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 the PCRpt and PCInitiate delegate. The C Flag has no meaning in the PCRpt and PCInitiate
message and MUST be set to 0 on transmission and MUST be ignored on message and MUST be set to 0 on transmission and MUST be ignored on
receipt. 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) to 1 in all PCRpt messages an LSP sets the D Flag (delegate) to 1 in all PCRpt messages
pertaining to the LSP. The PCE confirms the delegation by setting D pertaining to the LSP. The PCE confirms the delegation by setting D
Flag to 1 in all PCUpd messages pertaining to the LSP. The PCC Flag to 1 in all PCUpd messages pertaining to the LSP. The PCC
revokes the control of the LSP from the PCE by setting D Flag to 0 in revokes the control of the LSP from the PCE by setting D Flag to 0 in
PCRpt messages pertaining to the LSP. If the PCE wishes to PCRpt messages pertaining to the LSP. If the PCE wishes to
relinquish the control of the LSP, it sets D Flag to 0 in all PCUpd relinquish the control of the LSP, it sets D Flag to 0 in all PCUpd
messages pertaining to the LSP. 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 PCE SHOULD PLSP-ID in an LSP update request as per [RFC8231]. The D Flag and C
NOT send control request for LSP which is already delegated to the Flag are mutually exclusive in PCUpd message. The PCE SHOULD NOT
PCE, i.e. if the D flag is set in the PCUpd message, then C flag send control request for LSP which is already delegated to the PCE,
SHOULD NOT be set. If a PCC receives a PCUpd message with D flag set i.e. if the D Flag is set in the PCUpd message, then C Flag SHOULD
in the LSP object (i.e. LSP is already delegated) and the C flag is NOT be set. If a PCC receives a PCUpd message with D Flag set in the
also set (i.e. PCE is making a control request), the PCC MUST ignore LSP object (i.e. LSP is already delegated) and the C Flag is also
the C Flag. A PCC can decide to delegate the control of the LSP at set (i.e. PCE is making a control request), the PCC MUST ignore the
its own discretion. If the PCC grants or denies the control, it C Flag. A PCC can decide to delegate the control of the LSP at its
sends PCRpt message with D Flag set to 1 and 0 respectively in own discretion. If the PCC grants or denies the control, it sends
accordance with stateful PCEP [RFC8231]. If the PCC does not grant PCRpt message with D Flag set to 1 and 0 respectively in accordance
the control, it MAY choose to not respond, and the PCE MAY choose to with stateful PCEP [RFC8231]. If the PCC does not grant the control,
retry requesting the control preferably using exponentially it MAY choose to not respond, and the PCE MAY choose to retry
increasing timer. A PCE ignores the C Flag on the PCRpt message. requesting the control preferably using exponentially increasing
Note that, the PCUpd message with C flag set is received for a timer. A PCE ignores the C Flag on the PCRpt message. Note that,
currently non-delegated LSP (for which the PCE is requesting the PCUpd message with C Flag set is received for a currently non-
delegation), this MUST NOT trigger the error handling as specified in delegated LSP (for which the PCE is requesting delegation), this MUST
[RFC8231] (a PCErr with Error-type=19 (Invalid Operation) and error- NOT trigger the error handling as specified in [RFC8231] (a PCErr
value 1 (Attempted LSP Update Request for a non-delegated LSP)). with Error-type=19 (Invalid Operation) and error-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 LSP))
as the D flag would be unset in this update request. Further, in as the D Flag would be unset in this update request. Further, in
case of PLSP-ID of 0, the error condition as specified in [RFC8231] case of PLSP-ID of 0, the error condition as specified in [RFC8231]
(a PCErr with Error-type=19 (Invalid Operation) and error-value 3 (a PCErr with Error-type=19 (Invalid Operation) and error-value 3
(Attempted LSP Update Request for an LSP identified by an unknown (Attempted LSP Update Request for an LSP identified by an unknown
PSP-ID)) would be triggered. 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 specify how a initiated LSPs under the stateful PCE model. It also specify 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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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
A PCC implementation SHOULD allow the operator to configure the A PCC implementation SHOULD allow the operator to configure the
policy based on which it honors the request to control the LSPs. policy based on which it honors the request to control the LSPs.
This includes the handling of the case where an LSP control request This includes the handling of the case where an LSP control request
is received for an LSP that is currently delegated to some other PCE. is received for an LSP that is currently delegated to some other PCE.
Further, the operator MAY be to be allowed to trigger the LSP control A PCC implementation SHOULD also allow the operator to configure the
request for a particular LSP at the PCE. A PCE implementation SHOULD threshold rate based on which it accepts the delegation requests from
also allow the operator to configure an exponentially increasing the PCE. Further, the operator MAY be to be allowed to trigger the
timer to retry the control requests for which the PCE did not get a LSP control request for a particular LSP at the PCE. A PCE
response. implementation SHOULD also allow the operator to configure an
exponentially increasing timer to retry the control requests for
which the PCE did not get a response.
8.2. Information and Data Models 8.2. Information and Data Models
The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to
include mechanism to trigger the LSP control request. include mechanism to trigger the LSP control request.
8.3. Liveness Detection and Monitoring 8.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already detection and monitoring requirements in addition to those already
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