PCE Working Group A. Raghuram
Internet-Draft A. Goddard
Intended status: Standards Track C. Yadlapalli
Expires: December 6, 2019 AT&T
J. Karthik
S. Sivabalan
J. Parker
Cisco Systems, Inc.
M. Negi
Huawei Technologies
June 4, 2019
Ability for a stateful Path Computation Element (PCE) to request and
obtain control of a LSP
draft-ietf-pce-lsp-control-request-04
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/.
Raghuram, et al. Expires December 6, 2019 [Page 1]
Internet-Draft LSP Control Request June 2019
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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 December 6, 2019.
Copyright Notice
Copyright (c) 2019 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
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. LSP Control Request Flag . . . . . . . . . . . . . . . . . . 4
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 5
5.1. Huawei's Proof of Concept based on ONOS . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7.1. SRP Object Flags . . . . . . . . . . . . . . . . . . . . 7
8. Manageability Considerations . . . . . . . . . . . . . . . . 7
8.1. Control of Function and Policy . . . . . . . . . . . . . 7
8.2. Information and Data Models . . . . . . . . . . . . . . . 7
8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 7
8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 7
8.5. Requirements On Other Protocols . . . . . . . . . . . . . 8
8.6. Impact On Network Operations . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
Raghuram, et al. Expires December 6, 2019 [Page 2]
Internet-Draft LSP Control Request June 2019
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,
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.
Note that [RFC8231] specify a mechanism for a PCC to delegate an
orphaned LSP to another PCE. The mechanism defined in this document
can be used in conjunction to [RFC8231]. Ultimately, it is the PCC
that decides which PCE to delegate the orphaned LSP.
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 session. The procedures for granting and relinquishing
Raghuram, et al. Expires December 6, 2019 [Page 3]
Internet-Draft LSP Control Request June 2019
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
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. [RFC8281] 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 MUST 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.
Raghuram, et al. Expires December 6, 2019 [Page 4]
Internet-Draft LSP Control Request June 2019
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
control preferably using exponentially increasing timer. A PCE
ignores the C Flag on the PCRpt message. Note that, the PCUpd
message with C flag set is received for a currently non-delegated LSP
(for which the PCE is requesting delegation), this MUST NOT trigger
the error handling as specified in [RFC8231] (a PCErr with Error-
type=19 (Invalid Operation) and error-value 1 (Attempted LSP Update
Request for a non-delegated LSP)).
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). At the same time it
would trigger the error condition as specified in [RFC8231] (a PCErr
with Error-type=19 (Invalid Operation) and error-value 1 (Attempted
LSP Update Request for a non-delegated LSP)).
[RFC8281] 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 [RFC8281].
5. Implementation Status
[Note to the RFC Editor - remove this section before publication, as
well as remove the reference to RFC 7942.]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in RFC 7942
[RFC7942]. The description of implementations in this section is
intended to assist the IETF in its decision processes in progressing
drafts to RFCs. Please note that the listing of any individual
implementation here does not imply endorsement by the IETF.
Raghuram, et al. Expires December 6, 2019 [Page 5]
Internet-Draft LSP Control Request June 2019
Furthermore, no effort has been spent to verify the information
presented here that was supplied by IETF contributors. This is not
intended as, and must not be construed to be, a catalog of available
implementations or their features. Readers are advised to note that
other implementations may exist.
According to RFC 7942, "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
5.1. Huawei's Proof of Concept based on ONOS
The PCE function was developed in the ONOS open source platform.
This extension was implemented on a private version as a proof of
concept to enable multi-instance support.
o Organization: Huawei
o Implementation: Huawei's PoC based on ONOS
o Description: PCEP as a southbound plugin was added to ONOS. To
support multi-instance ONOS deployment in a cluster, this
extension in PCEP is used. Refer
https://wiki.onosproject.org/display/ONOS/PCEP+Protocol
o Maturity Level: Prototype
o Coverage: Full
o Contact: satishk@huawei.com
6. Security Considerations
The security considerations listed in [RFC8231] and [RFC8281] 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.
Raghuram, et al. Expires December 6, 2019 [Page 6]
Internet-Draft LSP Control Request June 2019
7. IANA Considerations
This document requests IANA actions to allocate code points for the
protocol elements defined in this document.
7.1. 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 [RFC8281]. IANA is
requested to make the following allocation in the aforementioned
registry.
Bit Description Reference
TBD LSP Control Request Flag (c-bit) This document
8. 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.
8.1. 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.
8.2. 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.
8.3. 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].
8.4. 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].
Raghuram, et al. Expires December 6, 2019 [Page 7]
Internet-Draft LSP Control Request June 2019
8.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any new requirements
on other protocols.
8.6. 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.
9. Acknowledgements
Thanks to Jonathan Hardwick to remind the authors to not use
suggested values in IANA section.
10. References
10.1. 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>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
Raghuram, et al. Expires December 6, 2019 [Page 8]
Internet-Draft LSP Control Request June 2019
10.2. Informative References
[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>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[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>.
[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>.
[I-D.ietf-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", draft-ietf-pce-pcep-
yang-11 (work in progress), March 2019.
Raghuram, et al. Expires December 6, 2019 [Page 9]
Internet-Draft LSP Control Request June 2019
Appendix A. Contributor Addresses
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: dhruv.ietf@gmail.com
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
Raghuram, et al. Expires December 6, 2019 [Page 10]
Internet-Draft LSP Control Request June 2019
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
Mahendra Singh Negi
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: mahendrasingh@huawei.com
Raghuram, et al. Expires December 6, 2019 [Page 11]