Internet DRAFT - draft-yang-pce-pcep-redundancy-policy
draft-yang-pce-pcep-redundancy-policy
PCE Working Group F. Yang
Internet-Draft X. Geng
Intended status: Standards Track T. Zhou
Expires: 12 January 2023 Huawei
11 July 2022
Path Computation Element Communication Protocol (PCEP) Extensions to
Redundancy Policy
draft-yang-pce-pcep-redundancy-policy-00
Abstract
PCEP is used to provide a communication between a PCC and a PCE.
This document defines the extensions to PCEP to support the
redundancy paths computation. Specifically, two new TLVs are defined
to support the request of redundancy path computation and protection
method, and one TLV is defined to distribute the Candidate Path Flag
of an SR Policy.
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 .
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 12 January 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. RP Object . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Redundancy Protection TLV . . . . . . . . . . . . . . . . 3
3.2. Protection Type TLV . . . . . . . . . . . . . . . . . . . 4
4. PCEP Extensions for Redundancy Policy . . . . . . . . . . . . 5
4.1. SR Policy Candidate Path Flag TLV . . . . . . . . . . . . 6
4.2. Path Binding TLV . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5.1. New TLV Type . . . . . . . . . . . . . . . . . . . . . . 7
5.2. PCEP Errors . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Redundancy protection [I-D.ietf-spring-sr-redundancy-protection] is a
generalized protection mechanism by replicating and transmitting
copies of flow packets on the redundancy node over multiple different
and disjoint paths, and further eliminating the redundant packets at
the merging node. To support redundancy protection in Segment
Routing, Redundancy Policy[I-D.geng-spring-redundancy-policy] is
provided to instantiate the segment lists of more than one disjoint
forwarding paths. This document extends the PCEP protocols to
support the request of redundancy paths computation and protection
method, and further distribute the flag of redundancy policy to
instantiate more than one segment lists for redundancy forwarding.
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2. Terminology
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. RP Object
The RP (Request Parameters) object defined in [RFC5440] is used to
specify various characteristics of the path computation request and
MUST be carried within each PCReq and PCRep messages. The format of
RP object is as follows:
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 |O|B|R| Pri |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request-ID-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Request Parameters Object
3.1. Redundancy Protection TLV
In order to request PCE to compute multiple redundancy forwarding
paths with the intention of redundancy protection, this document
defines a new TLV named Redundancy Protection TLV. The format of
Redundancy Protection TLV is shown as follows.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flag | Number | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Redundancy Protection TLV
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Where:
* Type: to be assigned by IANA.
* Length: 16-bit value to indicate the length of the value portion
in bytes.
* Flag: 8-bit bitmap to indicate the redundancy constraint of path
computation that PCC requires.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|R|U|U|U|U|U|U|U|
+-+-+-+-+-+-+-+-+
where:
a) R-Flag: One bit Redundancy Flag is used to indicate whether PCC
requires the common path computation or a redundancy path
computation. When redundancy flag bit is set to 0, it means PCC
requests a common path computation. When redundancy flag bit is
set to 1, it means PCC requests a redundancy path computation.
b) U-Flag: Unused and undefined
* Number: 8-bit value to indicate how many redundancy forwarding
paths that PCC requires. The range of the number is recommended
from 2 to 8.
* Reserved: 16-bit of reserved bits. SHOULD be set to zero on
transmission and MUST be ignored on receipt.
When PCC requests a redundancy path computation, it MUST include the
Redundancy Flag TLV in the RP object in PCReq message. When PCC
includes the Redundancy Flag TLV in a path computation request, PCE
would reply with the required number of redundancy forwarding paths
and the set of Redundancy Flag associated with the computed paths.
3.2. Protection Type TLV
As specified in [I-D.geng-spring-redundancy-policy], multiple
candidate paths can co-exist with different types of protection. In
order to differetiate the types of protection, a new TLV named
Protection Type TLV is defined. The format of Protection Type TLV is
shown as follows.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prot | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Protection Type TLV
where:
* Type: to be assigned by IANA.
* Length: 16-bit value to indicate the length of the value portion
in bytes.
* Protection: 4-bit value to indicate the protection type of path
computation that PCC requires. The following Table gives the
values and corresponding protection types.
+--------------+-------------------------+
| Value | Protection Type |
+--------------+-------------------------+
| 0 | No protection |
+--------------+-------------------------+
| 1 | Backup Protection |
+--------------+-------------------------+
| 2 | Redundancy Protection |
+--------------+-------------------------+
| 3-15 | Undefined |
+--------------+-------------------------+
Protection Type Values
* Reserved: 24-bit of reserved bits. SHOULD be set to zero on
transmission and MUST be ignored on receipt.
4. PCEP Extensions for Redundancy Policy
As per [I-D.ietf-pce-segment-routing-policy-cp], the mapping between
PCEP Associations and SR Policies is always one-to-one, and the
mapping between PCEP Tunnels and SR Policy Candidate Paths may be
either one-to-one or many-to-one. Regarding Redundancy Policy, the
mapping between PCEP Associations and Redundancy Policy is always
one-to-one. PCEP Tunnels and Redundancy Policy Candidate Paths are
always many-to-one. The definitions of SR Policy Association Type
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(SRPAT) and SR Policy Association Group (SRPAG) apply same to
Redundancy policy.
This document introduces a new SR Policy Candidate Path Attribute
called Flag, which identify the Flag of SR Policy Candidate Path
within the context of an SR Policy. This Flag identifier MUST NOT
change for a given LSP during its lifetime. When these rules are not
satisfied, the PCE MUST send a PCErr message with Error-Type = 26
"Association Error", Error Value = TBD4 "SR Policy Candidate Path
Flag Mismatch".
4.1. SR Policy Candidate Path Flag TLV
A new SR Policy Association Type TLV
[I-D.ietf-pce-segment-routing-policy-cp] called SR Policy Candidate
Path Flag TLV is defined to indicate the Flag of a candidate path.
The format of SR Policy Candidate Path Flag TLV is shown in
following.
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 (TBD3) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flag | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
SRPOLICY-CPPATH-Flag TLV
* Type: to be allocated by IANA.
* Length: specifies the length of the value field not including Type
and Length fields.
* Flag: 8-bit bitmap of Flag. A new registry "SR Policy Candidate
Path Flags" is created. One flag is defined at this writing:
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|R|U|U|U|U|U|U|U|
+-+-+-+-+-+-+-+-+
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where:
a) R-Flag: One bit Redundancy Flag is used to indicate the type of
candidate path. When R Flag is set, it represents the candidate
path is used for the redundancy forwarding.
b) U-Flag: Unused and undefined
* RESERVED: 3-octet of reserved bits. SHOULD be set to zero on
transmission and MUST be ignored on receipt.
4.2. Path Binding TLV
Since Redundancy Policy can be optionally associated with the Binding
Segment, specifically the Redundancy Segment, according to
[I-D.ietf-pce-segment-routing-policy-cp], the functionality of
specified-BSID-only is not mandatory to be enabled. It means that
the given Redundancy Segment is not required to be allocated and
programmed for the LSP to be operationally up. When there is a
Redundancy Segment associated with Redundancy Policy, TE-PATH-BINDIND
TLV [I-D.ietf-pce-binding-label-sid] is used to distribute Redundancy
Segment as the Binding Segment of Redundancy Policy.
5. IANA Considerations
5.1. New TLV Type
This document defines three new TLVs.
+-----------------+------------------------------------+----------------+
| Value | Name | Reference |
+-----------------+------------------------------------+----------------+
| TBD1 | Redundancy Protection TLV | This document |
+-----------------+------------------------------------+----------------+
| TBD2 | Protection Type TLV | This document |
+-----------------+------------------------------------+----------------+
| TBD3 | SR Policy Candidate Path Flag TLV | This document |
+-----------------+------------------------------------+----------------+
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5.2. PCEP Errors
This document defines one new Error-Value within the "Association
Error" Error-Type. IANA is requested to allocate new error values
within the "PCEP-ERROR Object Error Types and Values" sub-registry of
the PCEP Numbers registry, as follows:
+------------+------------------+-----------------------+-----------+
| Error-Type | Meaning | Error-value | Reference |
+------------+------------------+-----------------------+-----------+
| 26 | Association | | [RFC8697] |
| | Error | | |
+------------+------------------+-----------------------+-----------+
| | | TBD4: SR Policy | This I-D |
| | | Candidate Path | |
| | | Flag Mismatch | |
+------------+------------------+-----------------------+-----------+
6. Security Considerations
TBD
7. References
7.1. Normative References
[I-D.geng-spring-redundancy-policy]
Geng, X., Chen, M., and F. Yang, "Redundancy Policy for
Redundancy Protection", Work in Progress, Internet-Draft,
draft-geng-spring-redundancy-policy-02, 7 March 2022,
<https://www.ietf.org/archive/id/draft-geng-spring-
redundancy-policy-02.txt>.
[I-D.ietf-pce-segment-routing-policy-cp]
Koldychev, M., Sivabalan, S., Barth, C., Peng, S., and H.
Bidgoli, "PCEP extension to support Segment Routing Policy
Candidate Paths", Work in Progress, Internet-Draft, draft-
ietf-pce-segment-routing-policy-cp-07, 21 April 2022,
<https://www.ietf.org/archive/id/draft-ietf-pce-segment-
routing-policy-cp-07.txt>.
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[I-D.ietf-spring-sr-redundancy-protection]
Geng, X., Chen, M., Yang, F., Garvia, P. C., and G.
Mishra, "SRv6 for Redundancy Protection", Work in
Progress, Internet-Draft, draft-ietf-spring-sr-redundancy-
protection-01, 15 February 2022,
<https://www.ietf.org/archive/id/draft-ietf-spring-sr-
redundancy-protection-01.txt>.
[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>.
7.2. 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>.
Authors' Addresses
Fan Yang
Huawei
156 Beiqing Rd.
Beijing
100095
China
Email: shirley.yangfan@huawei.com
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Xuesong Geng
Huawei
156 Beiqing Rd.
Beijing
100095
China
Email: gengxuesong@huawei.com
Tianran Zhou
Huawei
156 Beiqing Rd.
Beijing
100095
China
Email: zhoutianran@huawei.com
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