Internet DRAFT - draft-fizgeer-pce-lsp-parameters
draft-fizgeer-pce-lsp-parameters
PCE Working Group O. Bachar
Internet-Draft M. Fizgeer
Intended status: Standards Track Ribbon Communication
Expires: 5 June 2023 2 December 2022
PCEP Extensions to support LSP parameters
draft-fizgeer-pce-lsp-parameters-00
Abstract
This document proposes extension to PCEP to configure LSP parameters.
Some of LSP parameters are needed to configure S-BFD for candidate
paths. An SR policy is identified by <headend, color, endpoint>
tuple. An SR policy can contain one or more candidate paths where
each candidate path is identified in PCEP by its uniquely assigned
PLSP-ID. The mechanism proposed in this document is applicable to
both MPLS and IPv6 data planes of SR.
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
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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 5 June 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Overview of Protocol Extensions . . . . . . . . . . . . . . . 4
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Processing . . . . . . . . . . . . . . . . . . . . . . . 4
4.3. Objects and TLVs . . . . . . . . . . . . . . . . . . . . 5
4.3.1. LSP S-BFD Capability . . . . . . . . . . . . . . . . 5
4.3.2. S-BFD parameters . . . . . . . . . . . . . . . . . . 5
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 7
6. Implementation Note . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 8
7.2. PCEP Errors . . . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Path Computation Element (PCE) Communication Protocol (PCEP)
[[RFC5440]] enables the communication between a Path Computation
Client (PCC) and a Path Computation Element (PCE), or between two
PCEs based on the PCE architecture [[RFC4655]].
PCEP Extensions for the Stateful PCE Model [[RFC8231]] describes a
set of extensions to PCEP to enable active control of Multiprotocol
Label Switching Traffic Engineering (MPLS-TE) and Generalized MPLS
(GMPLS) tunnels. [[RFC8281]] describes the setup and teardown of
PCE-initiated LSPs under the active stateful PCE model, without the
need for local configuration on the PCC, thus allowing for dynamic
centralized control of a network.
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PCEP Extensions for Segment Routing [[RFC8664]] specifies extensions
to the Path Computation Element Protocol (PCEP) that allow a stateful
PCE to compute and initiate Traffic Engineering (TE) paths, as well
as a PCC to request a path subject to certain constraint(s) and
optimization criteria in SR networks.
PCEP Extensions for Establishing Relationships Between Sets of LSPs
[[RFC8697]] 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.
Segment Routing Policy for Traffic Engineering details the concepts
of SR Policy and approaches to steering traffic into an SR Policy.
This document specifies PCEP extensions to signal additional
information to configure LSP attributes. This is accomplished via
the use of the existing LSPA object, by defining a new capability and
new TLVs.
2. Terminology
The following terminologies are used in this document:
* 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 Protocol. PCEP Tunnel: The entity
identified by the PLSP-ID, as per [I-D.koldychev-pce-
operational].
3. Motivation
S-BFD protocol is used for detecting failures in SR-TE tunnels.
There are several protocol parameters that need to be configured and
exchanged between PCEP speakers. As the parameters are associated to
SR-TE tunnels, they are exchanged via PCEP. The LSPS-BFD-Capability
TLV, the LSP-SBFD TLV and its sub-TLVs, defined in this document,
allow PCEP speakers to exchange additional information about S-BFD.
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4. Overview of Protocol Extensions
4.1. Overview
A new option to define S-BFD parameters is defined in this document.
The S-BFD parameters are only meant to be used for SR LSPs and with
PCEP peers which advertise SR capability.
A PCEP speaker indicates its ability to support S-BFD parameters
during the PCEP initialization phase, as follows. When the PCEP
session is created, it sends an Open message with an OPEN object that
contains the LSP-SBFD-Capability TLV (see Section 4.3.1).
If a PCEP speaker receives the PCEP LSP-SBFD-Capability TLV with B
flag = 1 in the Open object, then it means its peer is capable to
receive and to send S-BFD TLVs towards that peer.
If a PCEP speaker has not received this TLV in the Open object, or if
it receives it with B flag set to 0, then it MUST NOT send any S-BFD
TLVs in LSPA object towards that peer.
4.2. Processing
If a PCEP speaker is capable of S-BFD and its peer is capable of
S-BFD, then the PCEP speaker MAY send LSP-SBFD TLV towards that peer,
to report the S-BFD state (Enabled/Disabled) for the configured LSP.
The LSP-SBFD TLV shall be sent as an optional TLV in the LSPA object.
A PCC shall send it in the PCRpt message.
A PCE shall send it in the PCInit or in the PCUpd message. If the
LSP-SBFD TLV is received from a PCEP peer with the B flag set to 1,
then S-BFD shall be applied for specified LSP. If PCC received this
TLV via PCUpd with B=0 and there is no S-BFD applied for the LSP,
then the PCC shall IGNORE the TLV.
If PCE received this TLV with B=0 and there is no S-BFD applied for
the LSP (editing a PCC-initiated LSP) then it shall IGNORE it. If
B=0 and LSP-BFD-Parameters sub-TLV is received, then the PCEP speaker
shall IGNORE the sub-TLV.
In some implementations there is limitation that LSPs in the same
association group must have same S-BFD parameter values.
Editor note: Alternatively, it can be defined implicitly as follows:
If the LSP-SBFD TLV is not received from PCEP peer but there is S-BFD
for that LSP then S-BFD shall be removed for specified LSP.
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4.3. Objects and TLVs
4.3.1. LSP S-BFD Capability
The LSP-SBFD-Capability TLV is an optional TLV. It MAY be carried
within an OPEN object sent by PCEP speaker in an Open message to a
PCEP peer to indicate it supports SBFD capability.
The LSP-SBFD-Capability TLV has the following format:
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |B|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD1
Length: 4
B: A PCEP speaker sets this bit to 1 to indicate that it is capable
of S-BFD, and it supports configuring the S-BFD via PCEP
4.3.2. S-BFD parameters
4.3.2.1. LSP S-BFD TLV
The PCEP LSP-SBFD TLV is an optional TLV. It MAY be carried within
the LSPA object.
The PCEP LSP-SBFD TLV has the following format:
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |B|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional sub-TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* Type: TBD2
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* Length: The total length in bytes of the remainder of the TLV,
that is, excluding the Type and Length fields. B flag: Enable/
Disable S-BFD for this LSP. If B=1 then S-BFD will be enabled.
If B=0 then S-BFD will be disabled for that LSP. If the PCEP
speaker received LSP-SBFD TLV from PCEP peer with B flag is set to
0 then S-BFD shall be removed for specified LSP
4.3.2.2. LSP-SBFD Parameters sub-TLV
The PCEP LSP-BFD-Parameters sub-TLV is optional. It MAY be carried
within the LSP-SBFD TLV. The PCEP LSP-BFD-Parameters sub-TLV has the
following format:
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Min Tx Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Multiplier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD3
Length: 8
Min Tx Interval: 32 bits - Specify the Minimal Transmit Interval
(microseconds). Default "1000000".
Multiplier: 1..255
Procedure
If B=0 and LSP-BFD-Parameters sub-TLV is received, then the PCEP
speaker shall IGNORE the sub-TLV.
4.3.2.3. LSP-SBFD-Discriminator sub-TLV
The PCEP LSP-SBFD-Discriminator sub-TLV and is optional TLV. It MAY
be carried within the LSP-SBFD TLV. The PCEP LSP-SBFD-Discriminator
sub-TLV has the following format:
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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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD4
Length: 4
Remote Discriminator: 32 bits
Procedure
If B=0 and LSP-SBFD-Discriminator sub-TLV is received, then the PCEP
speaker shall IGNORE the LSP-SBFD-Discriminator sub-TLV.
5. Error Handling
If a PCEP speaker has not received S-BFD-Capability TLV from a peer
in the Open object, and it received an LSP S-BFD TLV (see
Section 4.3.2.1) from that peer, then it MUST ignore the content of
the LSP S-BFD TLV, and it MUST return a PCErr message with Error-
Type=19 "Invalid Operation" with Error-value = TBD5 "SBFD capability
is not negotiated".
If Multiplier value in the LSP-SBFD-Parameters sub-TLV is not in the
legal range (1..255), then the PCEP Speaker MUST return a PCErr
message with Error-Type=23 "Bad parameter value" and Error-value =
TBD6 "Multiplier is out of range".
If Remote Discriminator value in the PCEP LSP-SBFD-Discriminator sub-
TLV is not in the legal range (i.e., it is zero), then the PCEP
Speaker MUST return a PCErr message with Error-Type=23 "Bad parameter
value" and Error-value = TBD8 "Remote Discriminator is out of range".
6. Implementation Note
In some implementations there is limitation that LSPs in the same
association group must have same S-BFD parameter values. If either
the Min Tx Interval, the Multiplier or the Remote Discriminator
values received in the LSP-BFD Parameters sub-TLVs for LSPs that are
members in the same Association Group are not identical, then the
PCEP Speaker SHOULD return a PCErr message with Error-Type=26
"Association Error" with Error-value TBD7 "Invalid S-BFD parameter
value"
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7. IANA Considerations
7.1. PCEP TLV Type Indicators
This document defines new TLVs and sub-TLVs for carrying additional
information about S-BFD. IANA is requested to make the assignment of
new values for the existing "PCEP TLV Type Indicators" registry as
follows:
+=======+================================+===============+
| Value | Description | Reference |
+=======+================================+===============+
| TBD1 | LSP-SBFD-Capability TLV | This document |
+-------+--------------------------------+---------------+
| TBD2 | LSP-SBFD TLV | This document |
+-------+--------------------------------+---------------+
| TBD3 | LSP-BFD-Parameters sub-TLV | This document |
+-------+--------------------------------+---------------+
| TBD4 | LSP-SBFD-DISCRIMINATOR sub-TLV | This document |
+-------+--------------------------------+---------------+
Figure 1
7.2. PCEP Errors
This document defines new Error-Values within the different Error-Types.
IANA is requested to allocate new types:</t>
<figure anchor="ure-2">
<artwork name="" type="" align="left" alt=""><![CDATA[
+============+=============+======================+===========+
| Error Type | Error Value | Meaning | Reference |
+============+=============+======================+===========+
| 19 | TBD5 | SBFD capability is | This |
| | | not negotiated | document |
+------------+-------------+----------------------+-----------+
| 23 | TBD6 | Multiplier is out of | This |
| | | range | document |
+------------+-------------+----------------------+-----------+
| 26 | TBD7 | Invalid S-BFD | This |
| | | parameter value | document |
+------------+-------------+----------------------+-----------+
| 26 | TBD8 | Remote Discriminator | This |
| | | is out of range | document |
+------------+-------------+----------------------+-----------+
Figure 2
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8. Security Considerations
This document defines one new type for association, which does
not add any new security concerns beyond those discussed in
[<xref target="RFC5440" format="default"/>],
[<xref target="RFC8231" format="default"/>],
[<xref target="RFC8664" format="default"/>],
[<xref target="RFC5880" format="default"/>] and
[<xref target="RFC8697" format="default"/> ]
in itself.
9. Acknowledgement
Would like to thank Avantika Sushil, Alexander Ferdman, Itay Katz and
Galina Mintz for review and suggestions.
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>.
[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>.
[RFC8697] Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
Dhody, D., and Y. Tanaka, "Path Computation Element
Communication Protocol (PCEP) Extensions for Establishing
Relationships between Sets of Label Switched Paths
(LSPs)", RFC 8697, DOI 10.17487/RFC8697, January 2020,
<https://www.rfc-editor.org/info/rfc8697>.
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[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
[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>.
10.2. Informative References
[RFC4655] Farrel, A., Vasseur, J.-P., 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>.
Appendix A. Contributors
Dhruv Dhody
Huawei Technologies Divyashree Techno Park, Whitefield Bangalore,
Karnataka 560066 India
Email: dhruv.ietf@gmail.com
Authors' Addresses
Orly Bachar
Ribbon Communication
Hasivim 30, Petah-Tikva
Israel
Email: orly.bachar@rbbn.com
Marina Fizgeer
Ribbon Communication
Hasivim 30, Petah-Tikva
Email: marina.fizgeer@rbbn.com
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