PCE Working Group A. Raghuram
Internet-Draft A. Goddard
Intended status: Standards Track C. Yadlapalli
Expires: April 28, 2017 AT&T
J. Karthik
S. Sivabalan
J. Parker
Cisco Systems, Inc.
D. Dhody
Huawei Technologies
October 25, 2016
Ability for a stateful PCE to request and obtain control of a LSP
draft-raghu-pce-lsp-control-request-01
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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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
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material or to cite them other than as "work in progress."
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This Internet-Draft will expire on April 28, 2017.
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. LSP Control Request Flag . . . . . . . . . . . . . . . . . . 3
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Stateful PCEP extensions [I-D.ietf-pce-stateful-pce] 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: an operation in which a PCC temporarily grants the
rights to modify one or more LSPs to a PCE, and such LSPs are
referred to as delegated LSPs.
o Revocation: an operation in which a PCC revokes the previously
granted rights to modify one or more LSPs from a PCE.
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For Redundant Stateful PCEs (section 5.7.4. of [I-D.ietf-pce-
stateful-pce]), 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
to take control. In this case, a mechanism is needed for a stateful
PCE to request control of one or more LSPs for a PCC, so that a newly
elected primary PCE can request to take over control.
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 using which a PCE can
request control of one or more LSPs from any PCC over stateful PCEP
channel. The procedures for granting and relinquishing control of
the LSPs are specified in accordance with the specification
[I-D.ietf-pce-stateful-pce].
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 SRP object is defined in [I-D.ietf-pce-stateful-pce] and
included here for ease of reference.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRP-ID-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The SRP Object
A new flag, the "LSP Control Request Flag" (C), is introduced in the
Stateful PCE Request Parameters (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. 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 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, 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
[I-D.ietf-pce-stateful-pce] . If the PCC does not grant the control,
the PCE may choose to retry requesting the control preferably using
exponentially increasing timer. A PCE ignores the C Flag on the
PCRpt message
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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.
5. Security Considerations
No additional security measure is required.
6. IANA Considerations
None.
7. Acknowledgements
TBD.
8. References
8.1. Normative References
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-16 (work in progress), September 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://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,
<http://www.rfc-editor.org/info/rfc5440>.
8.2. 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, <http://www.rfc-editor.org/info/rfc4657>.
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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
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: msiva@cisco.com
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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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