Internet DRAFT - draft-ietf-pce-lsp-extended-flags
draft-ietf-pce-lsp-extended-flags
PCE Q. Xiong
Internet-Draft ZTE Corporation
Intended status: Standards Track 23 October 2022
Expires: 26 April 2023
Label Switched Path (LSP) Object Flag Extension for Stateful PCE
draft-ietf-pce-lsp-extended-flags-09
Abstract
RFC 8231 describes a set of extensions to Path Computation Element
Communication Protocol (PCEP) to enable stateful control of MPLS-TE
and GMPLS Label Switched Paths (LSPs) via PCEP. One of the
extensions is the LSP object which includes a Flag field with a
length of 12 bits. However, all bits of the Flag field have already
been assigned in RFC 8231, RFC 8281, RFC 8623 and I-D.ietf-pce-
binding-label-sid.
[Note to RFC Editor - Replace I-D.ietf-pce-binding-label-sid to RFC
XXXX, once the RFC number is assigned.]
This document proposes to define a new LSP-EXTENDED-FLAG TLV for the
LSP object for an extended flag field.
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/.
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 26 April 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
extracted from this document must include Revised BSD License text as
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. PCEP Extension . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. The LSP-EXTENDED-FLAG TLV . . . . . . . . . . . . . . . . 3
3.2. Processing . . . . . . . . . . . . . . . . . . . . . . . 4
4. Advice for Specification of New Flags . . . . . . . . . . . . 5
5. Backward Compatibility . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6.1. LSP Object . . . . . . . . . . . . . . . . . . . . . . . 5
6.1.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . 5
6.1.2. LSP Extended Flags Field . . . . . . . . . . . . . . 6
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 6
8. Management Considerations . . . . . . . . . . . . . . . . . . 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
12.1. Normative References . . . . . . . . . . . . . . . . . . 7
12.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. WG Discussion . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[RFC5440] describes the Path Computation Element (PCE) Communication
Protocol (PCEP) which is used between a PCE and a Path Computation
Client (PCC) (or other PCE) to enable computation of Multi-protocol
Label Switching for Traffic Engineering (MPLS-TE) Label Switched Path
(LSP).
PCEP Extensions for the Stateful PCE Model [RFC8231] describes a set
of extensions to PCEP to enable active control of MPLS-TE and
Generalized MPLS (GMPLS) tunnels. One of the extensions is the LSP
object, which contains a flag field; bits in the flag field are used
to indicate delegation, synchronization, removal, etc.
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As defined in [RFC8231], the length of the flag field is 12 bits and
the values from bit 5 to bit 11 are used for operational,
administrative, remove, synchronize and delegate bits respectively.
The bit value 4 is assigned in [RFC8281] to identify the PCE-
Initiated LSPs. The bits from 1 to 3 are assigned in [RFC8623] for
Explicit Route Object (ERO)-compression, fragmentation and Point-to-
Multipoint (P2MP) respectively. The bit 0 is assigned in
[I-D.ietf-pce-binding-label-sid] to PCE-allocation. All bits of the
Flag field have been assigned already. This document extends the
flag field of the LSP Object for other use.
This document proposes to define a new LSP-EXTENDED-FLAG TLV for an
extended flag field in the LSP object.
2. Conventions used in this document
2.1. Terminology
The terminology is defined as [RFC5440] and [RFC8231].
2.2. 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.
3. PCEP Extension
The LSP Object is defined in Section 7.3 of [RFC8231]. This document
proposes to define a new LSP-EXTENDED-FLAG TLV for an extended flag
field in the LSP object.
3.1. The LSP-EXTENDED-FLAG TLV
The format of the LSP-EXTENDED-FLAG TLV follows the format of all
PCEP TLVs as defined in [RFC5440] and is shown in Figure 1.
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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=TBD1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// LSP Extended Flags //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Figure 1: LSP-EXTENDED-FLAG TLV Format
Type (16 bits): TBD1.
Length (16 bits): indicates the length of the value portion in bytes.
It MUST be in multiples of 4 and greater than 0.
LSP Extended Flags: this contains an array of units of 32-bit flags
numbered from the most significant as bit zero, where each bit
represents one LSP flag (for operation, feature, or state). The LSP
Extended Flags field SHOULD use the minimal amount of space needed to
encode the flag bits. Currently, no bits are assigned. Unassigned
bits MUST be set to zero on transmission and MUST be ignored on
receipt.
As an example of usage of the LSP-EXTENDED-FLAG TLV, the E-flag is
requested for entropy label configuration as proposed in
[I-D.peng-pce-entropy-label-position].
3.2. Processing
The LSP Extended Flags field is an array of units of 32 flags, to be
allocated starting from the most significant bit. The bits of the
LSP Extended Flags field will be assigned by future documents. This
document does not define any flags. Flags that an implementation is
not supporting MUST be set to zero on transmission. Implementations
that do not understand any particular flag MUST ignore the flag.
Note that PCEP peers MUST handle varying lengths of the LSP-EXTENDED-
FLAG TLV.
If a PCEP speaker receives the LSP-EXTENDED-FLAG TLV of a length more
than it currently supports or understands, it MUST ignore the bits
beyond that length.
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If a PCEP speaker receives the LSP-EXTENDED-FLAG TLV of a length less
than the one supported by the implementation, it MUST treat the bits
beyond the length to be unset.
4. Advice for Specification of New Flags
Following the model provided in [RFC8786] Section 3.1, we provide the
following advice for new specifications that define additional flags.
Each such specification is expected to describe the interaction
between these new flags and any existing flags. In particular, new
specifications are expected to explain how to handle the cases when
both new and pre-existing flags are set. They are also expected to
discuss any security implications of the additional flags (if any)
and their interactions with existing flags.
5. Backward Compatibility
The LSP-EXTENDED-FLAG TLV defined in this document does not introduce
any backward compatibility issues. An implementation that does not
understand or support the LSP-EXTENDED-FLAG TLV MUST ignore the TLV
as per [RFC5440]. It is expected that future documents that define
bits in the LSP-EXTENDED-FLAG TLV will also define the error case
handling required for missing LSP-EXTENDED-FLAG TLV if it MUST be
present.
Further, any additional bits in the LSP-EXTENDED-FLAG TLV that are
not understood by an implementation MUST be ignored. It is expected
that future documents that define bits in the LSP-EXTENDED-FLAG TLV
will take that into consideration.
6. IANA Considerations
6.1. LSP Object
6.1.1. PCEP TLV Type Indicators
IANA is requested to allocate the following TLV Type Indicator value
within the "PCEP TLV Type Indicators" subregistry of the "Path
Computation Element Protocol (PCEP) Numbers" registry:
+=======+===================+=================+
| Value | Description | Reference |
+=======+===================+=================+
| TBD1 | LSP-EXTENDED-FLAG | [This document] |
+-------+-------------------+-----------------+
Table 1
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6.1.2. LSP Extended Flags Field
IANA is requested to create a new subregistry called "LSP-EXTENDED-
FLAG TLV Flag Field", within the "Path Computation Element Protocol
(PCEP) Numbers" registry to manage the LSP Extended Flags field of
the LSP-EXTENDED-FLAG TLV. New values are assigned by Standards
Action [RFC8126]. Each bit should be tracked with the following
qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Defining RFC
No values are currently defined. Bits 0-31 should initially be
marked as "Unassigned". Bits with a higher ordinal than 31 will be
added to the registry in future documents if necessary.
7. Implementation Status
[NOTE TO RFC EDITOR : This whole section and the reference to
[RFC7942] is to be removed before publication as an RFC]
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 [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. 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 [RFC7942], "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".
At the time of posting this version of this document, there are no
known implementations of this TLV. It is believed that this would be
implemented alongside the documents that allocate flags in the TLV.
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8. Management Considerations
Implementations receiving set LSP Extended Flags that they do not
recognize MAY log this. That could be helpful for diagnosing
backward compatibility issues with future features that utilize those
flags.
9. Security Considerations
[RFC8231] sets out security considerations for PCEP when used for
communication with a stateful PCE. This document does not change
those considerations. For LSP Object processing, see [RFC8231].
The flags for the LSP object and their associated security
considerations are specified in [RFC8231], [RFC8281], [RFC8623], and
[I-D.ietf-pce-binding-label-sid].
This document provides for the future addition of flags in the LSP
Object. Any future document that specifies new flags must also
discuss any associated security implications. No additional security
issues are raised in this document beyond those that exist in the
referenced documents. Note that the [RFC8231] recommends that the
stateful PCEP extension are authenticated and encrypted using
Transport Layer Security (TLS) [RFC8253], as per the recommendations
and best current practices in [RFC7525]. Assuming that
recommendation is followed, then the flags will be protected by TLS.
10. Acknowledgements
The authors would like to thank Loa Andersson, Adrian Farrel, Aijun
Wang, and Gyan Mishra for their review, suggestions and comments to
this document.
11. Contributors
The following people have substantially contributed to this document:
Dhruv Dhody
Huawei Technologies
EMail: dhruv.ietf@gmail.com
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
12. References
12.1. Normative References
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[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>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
12.2. Informative References
[I-D.ietf-pce-binding-label-sid]
Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
and C. L. (editor), "Carrying Binding Label/Segment
Identifier (SID) in PCE-based Networks.", Work in
Progress, Internet-Draft, draft-ietf-pce-binding-label-
sid-15, 20 March 2022, <https://www.ietf.org/archive/id/
draft-ietf-pce-binding-label-sid-15.txt>.
[I-D.peng-pce-entropy-label-position]
Xiong, Q., Peng, S., and F. Qin, "PCEP Extension for SR-
MPLS Entropy Label Position", Work in Progress, Internet-
Draft, draft-peng-pce-entropy-label-position-08, 29 August
2022, <https://www.ietf.org/archive/id/draft-peng-pce-
entropy-label-position-08.txt>.
[RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "OSPF Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088,
January 2008, <https://www.rfc-editor.org/info/rfc5088>.
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[RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "IS-IS Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089,
January 2008, <https://www.rfc-editor.org/info/rfc5089>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>.
[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>.
[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>.
[RFC8623] Palle, U., Dhody, D., Tanaka, Y., and V. Beeram, "Stateful
Path Computation Element (PCE) Protocol Extensions for
Usage with Point-to-Multipoint TE Label Switched Paths
(LSPs)", RFC 8623, DOI 10.17487/RFC8623, June 2019,
<https://www.rfc-editor.org/info/rfc8623>.
[RFC8786] Farrel, A., "Updated Rules for Processing Stateful PCE
Request Parameters Flags", RFC 8786, DOI 10.17487/RFC8786,
May 2020, <https://www.rfc-editor.org/info/rfc8786>.
Appendix A. WG Discussion
The WG discussed the idea of a fixed length (with 32 bits) for LSP-
EXTENDED-FLAG TLV. Though 32 bits would be sufficient for quite a
while, the use of variable length with a multiple of 32-bits allows
for future extensibility where we would never run out of flags and
there would not be a need to define yet another TLV in the future.
Further, note that [RFC5088] and [RFC5089] use the same approach for
the PCE-CAP-FLAGS Sub-TLV and are found to be useful.
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Author's Address
Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan
Hubei, 430223
China
Email: xiong.quan@zte.com.cn
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