PCE Working Group S. Litkowski
Internet-Draft Orange
Intended status: Standards Track S. Sivabalan
Expires: August 7, 2019 Cisco Systems, Inc.
J. Tantsura
Apstra, Inc.
J. Hardwick
Metaswitch Networks
M. Negi
Huawei Technologies
February 3, 2019
Path Computation Element communication Protocol extension for
associating Policies and LSPs
draft-ietf-pce-association-policy-05
Abstract
This document introduces a simple mechanism to associate policies to
a group of Label Switched Paths (LSPs) via an extension to the Path
Computation Element (PCE) Communication Protocol (PCEP).
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Policy based Constraints . . . . . . . . . . . . . . . . 5
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Policy Association Group . . . . . . . . . . . . . . . . . . 7
5.1. Policy Parameters TLV . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7.1. Association object Type Indicators . . . . . . . . . . . 9
7.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 9
8. Manageability Considerations . . . . . . . . . . . . . . . . 9
8.1. Control of Function and Policy . . . . . . . . . . . . . 9
8.2. Information and Data Models . . . . . . . . . . . . . . . 9
8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 9
8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 10
8.5. Requirements On Other Protocols . . . . . . . . . . . . . 10
8.6. Impact On Network Operations . . . . . . . . . . . . . . 10
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
[RFC5440] describes the Path Computation Element communication
Protocol (PCEP) which enables the communication between a Path
Computation Client (PCC) and a Path Control Element (PCE), or between
two PCEs based on the PCE architecture [RFC4655]. [RFC5394] provides
additional details on policy within the PCE architecture and also
provides context for the support of PCE Policy.
PCEP Extensions for Stateful PCE Model [RFC8231] describes a set of
extensions to PCEP to enable active control of Multiprotocol Label
Switching Traffic Engineering (MPLS-TE) and Generalzied MPLS (GMPLS)
tunnels. [RFC8281] describes the setup and teardown of PCE-initiated
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LSPs under the active stateful PCE model, without the need for local
configuration on the PCC, thus allowing for a dynamic network.
Currently, the LSPs can either be signaled via Resource Reservation
Protocol Traffic Engineering (RSVP-TE) or can be segment routed as
specified in [I-D.ietf-pce-segment-routing].
[I-D.ietf-pce-association-group] introduces a generic mechanism to
create a grouping of LSPs which can then be used to define
associations between a set of LSPs and a set of attributes (such as
configuration parameters or behaviors) and is equally applicable to
stateful PCE (active and passive modes) and stateless PCE.
This document specifies a PCEP extension to associate one or more
LSPs with policies using the generic association mechanism.
A PCEP speaker may want to influence the PCEP peer with respect to
path selection and other policies. This document describes a PCEP
extension to associate policies by creating Policy Association Group
(PAG) and encoding this association in PCEP messages. The
specification is applicable to both stateful and stateless PCEP
sessions.
1.1. 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.
2. Terminology
The following terminology is used in this document.
Association parameters: As described in
[I-D.ietf-pce-association-group], the combination of the mandatory
fields Association type, Association ID and Association Source in
the ASSOCIATION object uniquely identify the association group.
If the optional TLVs - Global Association Source or Extended
Association ID are included, then they are included in combination
with mandatory fields to uniquely identifying the association
group.
Association information: As described in
[I-D.ietf-pce-association-group], the ASSOCIATION object could
include other optional TLVs based on the association types, that
provides 'information' related to the association.
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LSR: Label Switch Router.
LSR: Label Switch Router.
MPLS: Multiprotocol Label Switching.
PAG: Policy Association Group.
PCC: Path Computation Client. Any client application requesting a
path computation to be performed by a Path Computation Element.
PCE: Path Computation Element. An entity (component, application,
or network node) that is capable of computing a network path or
route based on a network graph and applying computational
constraints.
PCEP: Path Computation Element Communication Protocol.
3. Motivation
Paths computed using PCE can be subjected to various policies on both
PCE and PCC. For example, in a centralized traffic engineering
scenario, network operators may instantiate LSPs and specifies
policies for traffic steering, path monitoring, etc., for some LSPs
via the stateful PCE. Similarly, a PCC could request a user- or
service-specific policy to be applied at the PCE, such as constraints
relaxation to meet optimal QoS and resiliency.
PCEP speaker can use the generic mechanism as per
[I-D.ietf-pce-association-group] to associate a set of LSPs with a
policy, without the need to know the details of such a policy, which
simplifies network operations, avoids frequent software upgrades, as
well provides an ability to introduce new policy faster.
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PAG Y
{Service-Specific Policy
for constraint
Initiate & Monitor LSP relaxation}
| |
| PAG X PCReq |
V {Monitor LSP} {PAG Y} V
+-----+ ----------------> +-----+
_ _ _ _ _ _| PCE | | | PCE |
| +-----+ | ----------> +-----+
| PCEInitiate | | PCReq
|{PAG X} | | {PAG Y}
| | |
| .-----. | | .-----.
| ( ) | +----+ ( )
| .--( )--. | |PCC1|--.--( )--.
V ( ) | +----+ ( )
+---+ ( ) | ( )
|PCC|----( (G)MPLS network ) +----+ ( (G)MPLS network )
+---+ ( ) |PCC2|------( )
PAG X ( ) +----+ ( )
{Monitor LSP} '--( )--' '--( )--'
( ) ( )
'-----' '-----'
Case 1: Policy requested by PCE Case 2: Policy requested by
and enforced by PCC PCC and enforced by
PCE
Figure 1: Sample use-cases for carrying policies over PCEP session
3.1. Policy based Constraints
In the context of policy-enabled path computation [RFC5394], path
computation policies may be applied at both a PCC and a PCE.
Consider an Label Switch Router (LSR) with a policy enabled PCC, it
receives a service request via signaling, including over a Network-
Network Interface (NNI) or User Network Interface (UNI) reference
point, or receives a configuration request over a management
interface to establish a service. The PCC may also apply user- or
service-specific policies to decide how the path selection process
should be constrained, that is, which constraints, diversities,
optimization criterion, and constraint relaxation strategies should
be applied in order for the service LSP(s) to have a likelihood to be
successfully established and provide necessary QoS and resilience
against network failures. The user- or service-specific policies
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applied to PCC and are then passed to the PCE along with the Path
computation request, in the form of constraints [RFC5394].
PCEP speaker can use the generic mechanism as per
[I-D.ietf-pce-association-group] to associate a set of LSPs with
policy and its resulting path computation constraints. This would
simplify the path computation message exchanges in PCEP.
4. Overview
As per [I-D.ietf-pce-association-group], LSPs are associated with
other LSPs with which they interact by adding them to a common
association group. Grouping can also be used to define association
between LSPs and policies associated to them. One new Association
Type is defined in this document, based on the generic Association
object -
o Association type = TBD1 ("Policy Association Type") for Policy
Association Group (PAG).
[I-D.ietf-pce-association-group] specify the mechanism for the
capability advertisement of the association types supported by a PCEP
speaker by defining a ASSOC-Type-List TLV to be carried within an
OPEN object. This capability exchange for the association type
described in this document (i.e. Policy Association Type) MUST be
done before using the policy association. Thus the PCEP speaker MUST
include the Policy Association Type (TBD1) in the ASSOC-Type-List TLV
before using the PAG in the PCEP messages.
This Association-Type is operator-configured association in nature
and created by the operator manually on the PCEP peers. The LSP
belonging to this associations is conveyed via PCEP messages to the
PCEP peer. Operator-configured Association Range SHOULD NOT be set
for this association-type, and MUST be ignored, so that the full
range of association identifier can be utilized.
A PAG can have one or more LSPs and its associated policy. The
association parameters including association identifier, type
(Policy), as well as the association source IP address is manually
configured by the operator and is used to identify the PAG as
described in [I-D.ietf-pce-association-group]. The Global
Association Source and Extended Association ID MAY also be included.
As per the processing rules specified in section 5.4 of
[I-D.ietf-pce-association-group], if a PCEP speaker does not support
this Policy association-type, it would return a PCErr message with
Error-Type 26 (Early allocation by IANA) "Association Error" and
Error-Value 1 "Association-type is not supported". Since the PAG is
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opaque in nature, the PAG and the policy MUST be configured on the
PCEP peers as per the operator-configured association procedures.
All processing is as per section 5.4 of
[I-D.ietf-pce-association-group]. If a PCE speaker receives PAG in a
PCEP message, and the policy association information is not
configured, it MUST return a PCErr message with Error-Type TBD
"Association Error" and Error- Value 4 "Association unknown". If
some of the association information [I-D.ietf-pce-association-group]
(the TLVs defined in this document) received from the peer does not
match the local configured values, the PCEP speaker MUST reject the
PCEP message and send a PCErr message with Error-Type 26 (Early
allocation by IANA) "Association Error" and Error-Value 5 "Operator-
configured association information mismatch".
5. Policy Association Group
Association groups and their memberships are defined using the
ASSOCIATION object defined in [I-D.ietf-pce-association-group]. Two
object types for IPv4 and IPv6 are defined. The ASSOCIATION object
includes "Association type" indicating the type of the association
group. This document add a new Association type -
Association type = TBD1 ("Policy Association Type") for PAG.
PAG may carry optional TLVs including but not limited to -
o POLICY-PARAMETERS-TLV: Used to communicate opaque information
useful to apply the policy, described in Section 5.1.
o VENDOR-INFORMATION-TLV: Used to communicate arbitrary vendor
specific behavioral information, described in [RFC7470].
5.1. Policy Parameters TLV
The POLICY-PARAMETERS-TLV is an optional TLV that can be carried in
ASSOCIATION object (with "Policy Association Type") to carry opaque
information needed to apply the policy at the PCEP peer. In some
cases to apply a PCE policy successfully, it is required to also
associate some policy parameters that needs to be evaluated, to
successfully apply the said policy. This TLV is used to carry those
policy parameters. The TLV could include one or more policy related
parameter. The encoding format and the order MUST be known to the
PCEP peers, this could be done during configuration of policy (and
its association parameters) for the PAG. The TLV format is as per
the format of the PCEP TLVs, as defined in [RFC5440], and shown in
Figure 2. Only one POLICY-PARAMETERS-TLV can be carried and only the
first occurrence is processed and any others MUST be ignored.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Policy Parameters //
| |
+---------------------------------------------------------------+
Figure 2: The POLICY-PARAMETERS-TLV format
The type of the POLICY-PARAMETERS-TLV is TBD2 and it has a variable
length. The Value field is variable field padded to a 4-bytes
alignment; padding is not included in the Length field. The PCEP
peer implementation need to be aware of the encoding format, order,
and meaning of the 'Policy Parameters' well in advance based on the
policy. Note that from the protocol point of view this data is
opaque and can be used to carry parameters in any format understood
by the PCEP peers and associated to the policy. The exact use of
this TLV is beyond the scope of this document.
If the PCEP peer is unaware of the policy parameters associated with
the policy and it receives the POLICY-PARAMETERS-TLV, it MUST ignore
the TLV and SHOULD log this event. Further, if one or more
parameters received in the POLICY-PARAMETERS-TLV received by the PCEP
speaker are considered as unacceptable in the context of the
associated policy (e.g. out of range value, badly encoded value...),
the PCEP speaker MUST NOT apply the received policy and SHOULD log
this event.
Note that, the vendor specific behavioral information is encoded in
VENDOR-INFORMATION-TLV which can be used along with this TLV.
6. Security Considerations
This document defines one new type for association, which do not add
any new security concerns beyond those discussed in [RFC5440],
[RFC8231] and [I-D.ietf-pce-association-group] in itself.
Some deployments may find policy associations and their implications
as extra sensitive and thus should employ suitable PCEP security
mechanisms like [RFC8253]. Also extra care needs to be taken by the
implementation with respect to POLICY-PARAMETERS-TLV while decoding,
verifying and applying these policy variables.
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7. IANA Considerations
7.1. Association object Type Indicators
This document defines the following new association type originally
defined in [I-D.ietf-pce-association-group].
Value Name Reference
TBD1 Policy Association Type [This I.D.]
7.2. PCEP TLV Type Indicators
The following TLV Type Indicator values are requested within the
"PCEP TLV Type Indicators" subregistry of the "Path Computation
Element Protocol (PCEP) Numbers" registry:
Value Description Reference
TBD2 POLICY-PARAMETERS-TLV [This I.D.]
8. Manageability Considerations
8.1. Control of Function and Policy
An operator MUST be allowed to configure the policy associations at
PCEP peers and associate it with the LSPs. They MAY also allow
configuration to related policy parameters, in which case the an
operator MUST also be allowed to set the encoding format and order to
parse the associated policy parameters TLV.
8.2. Information and Data Models
An implementation SHOULD allow the operator to view the PAG
configured. Further implementation SHOULD allow to view the current
set of LSPs in the PAG. To serve this purpose, the PCEP YANG module
[I-D.ietf-pce-pcep-yang] includes association groups and can be used
for PAG.
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].
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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].
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 this document do not have any impact on network
operations in addition to those already listed in [RFC5440].
9. Acknowledgments
A special thanks to author of [I-D.ietf-pce-association-group], this
document borrow some of the text from it.
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>.
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[I-D.ietf-pce-association-group]
Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
Dhody, D., and Y. Tanaka, "PCEP Extensions for
Establishing Relationships Between Sets of LSPs", draft-
ietf-pce-association-group-07 (work in progress), December
2018.
10.2. Informative References
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
"Policy-Enabled Path Computation Framework", RFC 5394,
DOI 10.17487/RFC5394, December 2008,
<https://www.rfc-editor.org/info/rfc5394>.
[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,
<https://www.rfc-editor.org/info/rfc7470>.
[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>.
[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>.
[I-D.ietf-pce-segment-routing]
Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-14 (work in progress),
October 2018.
[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-09 (work in progress), October 2018.
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Appendix A. Contributor Addresses
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: dhruv.ietf@gmail.com
Qin Wu
Huawei Technologies
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
EMail: sunseawq@huawei.com
Clarence Filsfils
Cisco Systems, Inc.
Pegasus Parc
De kleetlaan 6a, DIEGEM BRABANT 1831
BELGIUM
Email: cfilsfil@cisco.com
Xian Zhang
Huawei Technologies
Bantian, Longgang District
Shenzhen 518129
P.R.China
EMail: zhang.xian@huawei.com
Udayasree Palle
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: udayasreereddy@gmail.com
Authors' Addresses
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Stephane Litkowski
Orange
EMail: stephane.litkowski@orange.com
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
EMail: msiva@cisco.com
Jeff Tantsura
Apstra, Inc.
EMail: jefftant.ietf@gmail.com
Jonathan Hardwick
Metaswitch Networks
100 Church Street
Enfield, Middlesex
UK
EMail: Jonathan.Hardwick@metaswitch.com
Mahendra Singh Negi
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: mahendrasingh@huawei.com
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