SPRING Working Group R. Chen
Internet-Draft ZTE Corporation
Intended status: Standards Track Y. Liu
Expires: 2 September 2024 China Mobile
K. Talaulikar
S. Sidor
Cisco Systems, Inc.
D. Zhao
ZTE Corporation
L. Changwang
New H3C Technologies
Z. Ali
Cisco Systems, Inc.
1 March 2024
Validity of SR Policy Candidate Path
draft-chen-spring-sr-policy-cp-validity-02
Abstract
An SR Policy comprises one or more candidate paths (CP) of which at a
given time one and only one may be active (i.e., installed in
forwarding and usable for steering of traffic). Each CP in turn may
have one or more SID-List of which one or more may be active; when
multiple SID-List are active then traffic is load balanced over them.
However, a candidate path is valid when at least one SID-List is
active. This candidate path validity criterion cannot meet the needs
of some scenarios.
This document defines the new candidate path validity criterion.
Status of This Memo
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This Internet-Draft will expire on 2 September 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Validity of a Candidate Path . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
SR Policy architecture are specified in [RFC9256]. An SR Policy
comprises one or more candidate paths (CP) of which at a given time
one and only one may be active (i.e., installed in forwarding and
usable for steering of traffic). Each CP in turn may have one or
more SID-List of which one or more may be active; when multiple SID-
List are active then traffic is load balanced over them. However, a
candidate path is valid when at least one SID-List is active. This
candidate path validity criterion cannot meet the needs of some
scenarios.
This document defines the new candidate path validity criterion, and
it does not change the segment list invalidation rules defined in SR
Policy architecture are specified in [RFC9256].
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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. Motivation
The candidate path validity criterion defined in [RFC9256] can't meet
the needs of the following scenarios:
+----------------------+
+---------| SL1(Weight 1, 100MB) |
+----------------+ | +----------------------+
| CP1 (200MB) |------+
+----------------+ | +----------------------+
+---------| SL2(Weight 1, 100MB) |
+----------------------+
Figure 1
The SR Policy POL1 has two candidate paths: CP1 and CP2, and CP1 is
the active candidate path (it is valid and has the highest
Preference). The two segment lists (SL1 and SL2) of CP1 are
installed as the forwarding instantiation of SR Policy POL1.
The CP1 carries a total of 200MB of traffic. Within the POL1, the
flow-based hashing over its each SL with a ratio 50%, that is each SL
carry 100MB of traffic. At this time, Use the segment list
invalidity rule defined in RFC9256, if it is determined that one of
the segment list is invalid, the remaining Segment List cannot carry
200MB of traffic. However, the CP1 is still active.
3. Validity of a Candidate Path
A headend MAY be informed about the validity control parameters of a
candidate path for an SR Policy <Color, Endpoint> by various means
including: via configuration, PCEP, or BGP. The detailed protocol
extension will be described in a separate document.
This document defines the following validity control parameters under
candidate Path to control the validity judgment of candidate Path:
* valid SL count: 8-bit value, The value is 1-0xff.
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Indicates the minimum number of valid segment Lists under the
active candidate path. When the number of valid segment Lists
under candidate path is greater than or equal to this field, the
candidate path is considered valid.
0xff indicates that the candidate path is considered valid only if
all the segment Lists are valid.
* valid SL weight: 32-bit value, The value is 0-0xffffffff.
Indicates the minimum value of the sum of the weights of the valid
segment List under the active candidate Path.
When the sum of the weights of the valid segment Lists under the
candidate path is greater than or equal to this field, the
candidate Path is considered valid.
0 indicates no requirement for weight.
0xffffffff indicates that the candidate path is considered valid
only if all the segment Lists are valid.
Candidate path is considered valid only when all three validity
control parameters are satisfied.
4. IANA Considerations
This document makes no request of IANA.
5. Security Considerations
The security considerations of segment routing in [RFC9256] are
applicable to this document.
6. Acknowledgements
TBD.
7. 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>.
[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>.
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[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
Authors' Addresses
Ran Chen
ZTE Corporation
Nanjing
China
Email: chen.ran@zte.com.cn
Yisong Liu
China Mobile
Beijing
China
Email: liuyisong@chinamobile.com
Ketan Talaulikar
Cisco Systems, Inc.
Email: ketant.ietf@gmail.com
Samuel Sidor
Cisco Systems, Inc.
Bratislava
Slovakia
Email: ssidor@cisco.com
Detao Zhao
ZTE Corporation
Nanjing
China
Email: zhao.detao@zte.com.cn
Changwang Lin
New H3C Technologies
Beijing
China
Email: linchangwang.04414@h3c.com
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Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
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