Internet DRAFT - draft-raghu-pce-lsp-control-request
draft-raghu-pce-lsp-control-request
PCE Working Group A. Raghuram
Internet-Draft A. Goddard
Intended status: Standards Track C. Yadlapalli
Expires: May 3, 2018 AT&T
J. Karthik
S. Sivabalan
J. Parker
Cisco Systems, Inc.
D. Dhody
Huawei Technologies
October 30, 2017
Ability for a stateful PCE to request and obtain control of a LSP
draft-raghu-pce-lsp-control-request-05
Abstract
The stateful Path Computation Element (PCE) communication Protocol
(PCEP) extensions provide stateful control of Multiprotocol Label
Switching (MPLS) Traffic Engineering Label Switched Paths (TE LSP)
via PCEP, for a model where a Path Computation Client (PCC) delegates
control over one or more locally configured LSPs to a stateful PCE.
There are use-cases in which a stateful PCE may wish to request and
obtain control of one or more LSPs from a PCC. This document
describes a simple extension to stateful PCEP to achieve such an
objective.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 3, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. LSP Control Request Flag . . . . . . . . . . . . . . . . . . 4
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6.1. SRP Object Flags . . . . . . . . . . . . . . . . . . . . 5
7. Manageability Considerations . . . . . . . . . . . . . . . . 6
7.1. Control of Function and Policy . . . . . . . . . . . . . 6
7.2. Information and Data Models . . . . . . . . . . . . . . . 6
7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 6
7.4. Verify Correct Operations . . . . . . . . . . . . . . . . 6
7.5. Requirements On Other Protocols . . . . . . . . . . . . . 6
7.6. Impact On Network Operations . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Stateful PCEP extensions [RFC8231] specifies a set of extensions to
PCEP [RFC5440] to enable stateful control of TE LSPs between and
across PCEP sessions in compliance with [RFC4657]. It includes
mechanisms to effect LSP state synchronization between PCCs and PCEs,
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delegation of control of LSPs to PCEs, and PCE control of timing and
sequence of path computations within and across PCEP sessions. The
stateful PCEP defines the following two useful network operations:
o Delegation: As per [RFC8051], an operation to grant a PCE
temporary rights to modify a subset of LSP parameters on one or
more LSPs of a PCC. LSPs are delegated from a PCC to a PCE and
are referred to as "delegated" LSPs.
o Revocation: As per [RFC8231], an operation performed by a PCC on a
previously delegated LSP. Revocation revokes the rights granted
to the PCE in the delegation operation.
For Redundant Stateful PCEs (section 5.7.4. of [RFC8231]), during a
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
proprietary election mechanism to decide which PCE would take
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
elected primary PCE can request to take over control.
In case of virtualized PCEs (vPCE) running as virtual network
function (VNF), as the computation load in the network increases, a
new instance of vPCE could be instantiated to balance the current
load. The PCEs could use proprietary algorithm to decide which LSPs
to be assigned to the new vPCE. Thus having a mechanism for the PCE
to request control of some LSPs is needed.
In some deployments, the operator would like to use stateful PCE for
global optimization algorithms but would still like to keep the
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
delegation once done.
This specification provides a simple extension, by using this a PCE
can request control of one or more LSPs from any PCC over the
stateful PCEP channel. The procedures for granting and relinquishing
control of the LSPs are specified in accordance with the
specification [RFC8231].
2. Terminology
The following terminologies are used in this document:
PCC: Path Computation Client.
PCE: Path Computation Element
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PCEP: Path Computation Element communication Protocol.
PCRpt: Path Computation State Report message.
PCUpd: Path Computation Update Request message.
PLSP-ID: A PCEP-specific identifier for the LSP.
3. LSP Control Request Flag
The Stateful PCE Request Parameters (SRP) object is defined in
[RFC8231], it includes a Flags field.
[I-D.ietf-pce-pce-initiated-lsp] defines a R (LSP-REMOVE) flag.
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
indicate that, it wishes to gain control of LSP(s). The LSP is
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
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
delegate. The flag has no meaning in the PCRpt and PCInitiate
message and SHOULD be set to 0 on transmission and MUST be ignored on
receipt.
4. Operation
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
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
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
relinquish the control of the LSP, it sets D Flag to 0 in all PCUpd
messages pertaining to the LSP.
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
requests control is identified by the PLSP-ID. The PLSP-ID of 0
indicates that the PCE wants control over all LSPs originating from
the PCC. If the LSP(s) is/are already delegated to the PCE making
the request, the PCC ignores the C Flag. A PCC can decide to
delegate the control of the LSP at its own discretion. If the PCC
grants or denies the control, it sends PCRpt message with D Flag set
to 1 and 0 respectively in accordance with according with stateful
PCEP [RFC8231] . If the PCC does not grant the control, it MAY choose
to not respond, and the PCE may choose to retry requesting the
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control preferably using exponentially increasing timer. A PCE
ignores the C Flag on the PCRpt message.
In case multiple PCEs request control over an LSP, and if the PCC is
willing to grant the control, the LSP MUST be delegated to only one
PCE chosen by the PCC based on its local policy.
It should be noted that a legacy implementation of PCC, that does not
understand the C flag in PCUpd message, would simply ignore the flag
and the request to grant control over the LSP.
[I-D.ietf-pce-pce-initiated-lsp] describes the setup, maintenance and
teardown of PCE-initiated LSPs under the stateful PCE model. It also
specify how a PCE MAY obtain control over an orphaned LSP that was
PCE-initiated. A PCE implementation can apply the mechanism
described in this document in conjunction with those in
[I-D.ietf-pce-pce-initiated-lsp].
5. Security Considerations
The security considerations listed in [RFC8231] apply to this
document as well. However, this document also introduces a new
attack vectors. An attacker may flood the PCC with request to
delegate all its LSPs at a rate which exceeds the PCC's ability to
process them, either by spoofing messages or by compromising the PCE
itself. The PCC can simply ignore these messages with no extra
actions. Securing the PCEP session using mechanism like Transport
Layer Security (TLS) [RFC8253] is RECOMMENDED.
6. IANA Considerations
This document requests IANA actions to allocate code points for the
protocol elements defined in this document.
6.1. SRP Object Flags
The SRP object is defined in [RFC8231] and the registry to manage the
Flag field of the SRP object is requested in
[I-D.ietf-pce-pce-initiated-lsp]. IANA is requested to make the
following allocation in the aforementioned registry.
Bit Description Reference
TBD LSP Control Request Flag (c-bit) This document
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7. Manageability Considerations
All manageability requirements and considerations listed in [RFC5440]
and [RFC8231] apply to PCEP protocol extensions defined in this
document. In addition, requirements and considerations listed in
this section apply.
7.1. Control of Function and Policy
A PCE or PCC implementation SHOULD allow the operator to configure
the policy based on which it honor the request to control the LSPs.
Further, the operator MAY be to be allowed to trigger the LSP control
request at the PCE.
7.2. Information and Data Models
The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to
include mechanism to trigger the LSP control request.
7.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
7.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC5440] and [RFC8231].
7.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any new requirements
on other protocols.
7.6. Impact On Network Operations
Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP
extensions defined in this document. Further, the mechanism
described in this document can help the operator to request control
of the LSPs at a particular PCE.
8. Acknowledgements
Thanks to Jonathan Hardwick to remind the authors to not use
suggested values in IANA section.
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
9.2. Informative References
[I-D.ietf-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", draft-ietf-pce-pce-initiated-lsp-11 (work in
progress), October 2017.
[I-D.ietf-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and j.
jefftant@gmail.com, "A YANG Data Model for Path
Computation Element Communications Protocol (PCEP)",
draft-ietf-pce-pcep-yang-05 (work in progress), June 2017.
[RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol Generic
Requirements", RFC 4657, DOI 10.17487/RFC4657, September
2006, <https://www.rfc-editor.org/info/rfc4657>.
[RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
Stateful Path Computation Element (PCE)", RFC 8051,
DOI 10.17487/RFC8051, January 2017,
<https://www.rfc-editor.org/info/rfc8051>.
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[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
Authors' Addresses
Aswatnarayan Raghuram
AT&T
200 S Laurel Aevenue
Middletown, NJ 07748
USA
Email: ar2521@att.com
Al Goddard
AT&T
200 S Laurel Aevenue
Middletown, NJ 07748
USA
Email: ag6941@att.com
Chaitanya Yadlapalli
AT&T
200 S Laurel Aevenue
Middletown, NJ 07748
USA
Email: cy098d@att.com
Jay Karthik
Cisco Systems, Inc.
125 High Street
Boston, Massachusetts 02110
USA
Email: jakarthi@cisco.com
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Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: msiva@cisco.com
Jon Parker
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: jdparker@cisco.com
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
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