PCE Working Group S. Sivabalan
Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems, Inc.
Expires: April 8, 2016 J. Tantsura
Ericsson
J. Hardwick
Metaswitch Networks
October 6, 2015
Conveying policies associated with traffic engineering paths over PCEP
session
draft-sivabalan-pce-policy-identifier-00.txt
Abstract
This document describes a simple extension to the Path Computation
Element (PCE) Communication Protocol (PCEP) using which a PCEP
speaker can enforce one or more policies on the other PCEP speaker.
A policy is represented by a numeric value which can be interpreted
only by the receiving PCEP speaker. Using the proposed extension, a
path computation client (PCC) can signal one or more policies that
must be taken into consideration by a PCE during path computation.
Similarly, when initiating or updating a path, a stateful PCE can
signal one or more policies (e.g., traffic steering rules) that a PCC
is expected to apply to the path.
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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Drafts is at http://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
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on April 8, 2016.
Copyright Notice
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Policy Identifier TLV . . . . . . . . . . . . . . . . . . . . 4
5. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP) for
communication between a Path Computation Client (PCC) and a PCE or
between a pair of PCEs. [I-D.ietf-pce-stateful-pce] specifies
extension to PCEP that allows a PCC to delegate its LSPs to a PCE.
The PCE can then update the state of LSPs delegated to it.
[I-D.ietf-pce-pce-initiated-lsp] specifies a mechanism allowing a PCE
to dynamically instantiate, maintain, and tear down Label Switched
Paths (LSPs) without the need for configuring those LSPs on the PCC.
Currently, the LSPs can either be signaled via RSVP-TE or can be
segment routed as specified in [I-D.ietf-pce-segment-routing].
As described in the next section, a PCEP speaker may want to
influence its PCEP counterpart with respect to path selection and
other policies. This document describes a PCEP extension to signal
policy identifier represented by numeric value using OPTIONAL PCEP
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TLV. The specification is applicable to both stateful and stateless
PCEP sessions.
2. Motivation
Paths computed using PCEP are subject to various policies on both PCE
as well as PCC. For example, in a centralized traffic engineering
scenario, network operators may instantiate LSPs and specifies
policies for traffic steering, path monitoring, etc., for those LSPs
via stateful PCE. Similarly, a PCC can request a path that is
diverse from any other path originating from other PCC(s) from a
stateful PCE. With a current state of PCEP, introducing such policy
requires new PCEP extension. A generic mechanism that allows a PCEP
speaker to specify the path policies without the need to know the
details of such policies simplifies network operations, avoids
frequent software upgrades, as well provides an ability to introduce
new policy faster.
Policy-ID Y
Initiate & Monitor LSP {Disjoint paths}
| |
| PCReq |
V {policy-ID Y} V
+-----+ ----------------> +-----+
_ _ _ _ _ _| PCE | | | PCE |
| +-----+ | ----------> +-----+
| PCEInitiate | | PCReq
|{policy-ID X} | | {policy-ID Y}
| | |
| .-----. | | .-----.
| ( ) | +----+ ( )
| .--( )--. | |PCC1|--.--( )--.
V ( ) | +----+ ( )
+---+ ( ) | ( )
|PCC|----( MPLS network ) +----+ ( MPLS network )
+---+ ( ) |PCC2|------( )
Policy ID X ( ) +----+ ( )
{Monitor LSP} '--( )--' '--( )--'
( ) ( )
'-----' '-----'
Case 1: Policy initiated by PCE Case 2: Policy initiated by PCC
and enforced by PCC and enforced by PCE
Figure 1: Sample use-cases for carrying policies over PCEP session
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3. Terminology
The following terminologies are used in this document:
LSP: Label Switched Path.
PCC: Path Computation Client.
PCE: Path Computation Element
PCEP: Path Computation Element Protocol.
TLV: Type, Length, and Value.
4. Policy Identifier TLV
The new optional TLV is called "POLICY-ID-TLV" whose format is shown
in the diagram below is defined to indicate the policies applied to a
path. This TLV is associated with the RP or SRP objects specified
in[RFC5440] and [I-D.ietf-pce-stateful-pce] respectively. The type
of this TLV is to be allocated by IANA.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |M| Policy ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ VENDOR-INFORMATION-TLV (optional) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Format of POLICY-ID-TLV
The TLV is formatted according to the rules specified in [RFC5440].
The body of the POLICY-ID-TLV contains one 1-Octet flags and 3-Octet
policy identifier. By default, a policy is OPTIONAL. If the M-flag
is set, the policy is considered MANDATORY. This TLV can optionally
carry vendor-specific information via VENDOR-INFORMATION-TLV whose
format and processing rules are specified in [RFC7470]. The presence
of VENDOR-INFORMATION-TLV is detected based on the TLV length, and
the content and processing rule of vendor-specific information is
outside the scope of this specification.
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5. Operation
A single message MAY contain more than one POLICY-ID-TLVs. In case,
a a speaker receives a message containing multiple POLICY-ID-TLVs
with the same policy ID, it MUST ignore all except for the first one
itencounters in the message. If a PCEP speaker does not recognize
the TLV, it MUST ignore the TLV in accordance with ([RFC5440]). If a
PCEP speaker recognizes the TLV but does not support a mandatory
policy included in the message, it MUST ignore the whole message and
send PCErr with Error-Type = 2 (Capability not supported) as well
include the POLICY-ID-TLV corresponding to the unsupported policies.
When requesting a path from a PCE using a PCReq message ([RFC5440]),
a PCC MAY include the POLICY-ID-TLV in the RP object. The PCE MUST
take into account all the policies included in the PCReq otherwise it
MUST ignore the whole message and send PCErr message as mentioned
above.
In the case of stateful PCE, POLICY-ID-TLV MAY be included in PCReq,
PCRpt, PCUpd, and PCInitiate messages as well. When including
POLICY-ID-TLV in PCRpt message, the SRP object MUST be present even
in cases when the SRP-ID-number is the reserved value of 0x00000000.
6. Security Considerations
No additional security measure is required.
7. IANA Considerations
IANA is requested to allocate a new code point in the PCEP TLV Type
Indicators registry, as follows:
Value Description Reference
TBD POLICY-ID-TLV This document
8. Acknowledgements
9. Normative 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-04 (work in
progress), April 2015.
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[I-D.ietf-pce-segment-routing]
Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,
Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick,
"PCEP Extensions for Segment Routing", draft-ietf-pce-
segment-routing-06 (work in progress), August 2015.
[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-11 (work in progress), April 2015.
[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>.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206,
DOI 10.17487/RFC4206, October 2005,
<http://www.rfc-editor.org/info/rfc4206>.
[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>.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
2009, <http://www.rfc-editor.org/info/rfc5462>.
[RFC7470] Zhang, F. and A. Farrel, "Conveying Vendor-Specific
Constraints in the Path Computation Element Communication
Protocol", RFC 7470, DOI 10.17487/RFC7470, March 2015,
<http://www.rfc-editor.org/info/rfc7470>.
Authors' Addresses
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: msiva@cisco.com
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Clarence Filsfils
Cisco Systems, Inc.
Pegasus Parc
De kleetlaan 6a, DIEGEM BRABANT 1831
BELGIUM
Email: cfilsfil@cisco.com
Jeff Tantsura
Ericsson
300 Holger Way
San Jose, CA 95134
USA
Email: jeff.tantsura@ericsson.com
Jonathan Hardwick
Metaswitch Networks
100 Church Street
Enfield, Middlesex
UK
Email: Jonathan.Hardwick@metaswitch.com
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