draft-ietf-idr-sr-policy-path-segment-02.txt   draft-ietf-idr-sr-policy-path-segment-03.txt 
Interdomain Routing Working Group C. Li Interdomain Routing Working Group C. Li
Internet-Draft Z. Li Internet-Draft Z. Li
Intended status: Standards Track Huawei Technologies Intended status: Standards Track Huawei Technologies
Expires: May 6, 2021 H. Chen Expires: September 10, 2021 H. Chen
China Telecom China Telecom
W. Cheng W. Cheng
China Mobile China Mobile
K. Talaulikar K. Talaulikar
Cisco Systems Cisco Systems
November 2, 2020 March 9, 2021
SR Policy Extensions for Path Segment and Bidirectional Path SR Policy Extensions for Path Segment and Bidirectional Path
draft-ietf-idr-sr-policy-path-segment-02 draft-ietf-idr-sr-policy-path-segment-03
Abstract Abstract
A Segment Routing (SR) policy is a set of candidate SR paths A Segment Routing (SR) policy is a set of candidate SR paths
consisting of one or more segment lists with necessary path consisting of one or more segment lists with necessary path
attributes. For each SR path, it may also have its own path attributes. For each SR path, it may also have its own path
attributes, and Path Segment is one of them. A Path Segment is attributes, and Path Segment is one of them. A Path Segment is
defined to identify an SR path, which can be used for performance defined to identify an SR path, which can be used for performance
measurement, path correlation, and end-2-end path protection. Path measurement, path correlation, and end-2-end path protection. Path
Segment can be also used to correlate two unidirectional SR paths Segment can be also used to correlate two unidirectional SR paths
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Path Segment in SR Policy . . . . . . . . . . . . . . . . . . 3 3. Path Segment in SR Policy . . . . . . . . . . . . . . . . . . 3
3.1. SR Path Segment Sub-TLV . . . . . . . . . . . . . . . . . 5 3.1. SR Path Segment Sub-TLV . . . . . . . . . . . . . . . . . 5
4. SR Policy for Bidirectional Path . . . . . . . . . . . . . . 6 4. SR Policy for Bidirectional Path . . . . . . . . . . . . . . 7
4.1. Reverse Path Segment List Sub-TLV . . . . . . . . . . . . 7 4.1. Reverse Path Segment List Sub-TLV . . . . . . . . . . . . 7
5. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6.1. Existing Registry: BGP Tunnel Encapsulation Attribute 6.1. Existing Registry: BGP Tunnel Encapsulation Attribute
sub-TLVs . . . . . . . . . . . . . . . . . . . . . . . . 9 sub-TLVs . . . . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10 10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 10 10.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
Segment routing (SR) [RFC8402] is a source routing paradigm that Segment routing (SR) [RFC8402] is a source routing paradigm that
explicitly indicates the forwarding path for packets at the ingress explicitly indicates the forwarding path for packets at the ingress
node. The ingress node steers packets into a specific path according node. The ingress node steers packets into a specific path according
to the Segment Routing Policy ( SR Policy) as defined in to the Segment Routing Policy ( SR Policy) as defined in
[I-D.ietf-spring-segment-routing-policy]. For distributing SR [I-D.ietf-spring-segment-routing-policy]. For distributing SR
policies to the headend, [I-D.ietf-idr-segment-routing-te-policy] policies to the headend, [I-D.ietf-idr-segment-routing-te-policy]
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scenarios, for example, mobile backhaul transport network, there are scenarios, for example, mobile backhaul transport network, there are
requirements to support bidirectional path. However, there is no requirements to support bidirectional path. However, there is no
path identification information for each Segment List in the SR path identification information for each Segment List in the SR
Policies defined in [I-D.ietf-spring-segment-routing-policy]. Also, Policies defined in [I-D.ietf-spring-segment-routing-policy]. Also,
the SR Policies defined in [I-D.ietf-spring-segment-routing-policy] the SR Policies defined in [I-D.ietf-spring-segment-routing-policy]
only supports unidirectional SR paths. only supports unidirectional SR paths.
Therefore, this document defines the extension to SR policies that Therefore, this document defines the extension to SR policies that
carry Path Segment in the Segment List and support bidirectional carry Path Segment in the Segment List and support bidirectional
path. The Path Segment can be a Path Segment in SR-MPLS path. The Path Segment can be a Path Segment in SR-MPLS
[I-D.ietf-spring-mpls-path-segment] , or other IDs that can identify [I-D.ietf-spring-mpls-path-segment] and SRv6
a path. Also, this document defines extensions to BGP to distribute [I-D.ietf-spring-srv6-path-segment], or other IDs that can identify a
SR policies carrying Path Segment and bidirectional path information. path. Also, this document defines extensions to BGP to distribute SR
policies carrying Path Segment and bidirectional path information.
2. Terminology 2. Terminology
This memo makes use of the terms defined in [RFC8402] and This memo makes use of the terms defined in [RFC8402] and
[I-D.ietf-idr-segment-routing-te-policy]. [I-D.ietf-idr-segment-routing-te-policy].
2.1. Requirements Language 2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
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Type: to be assigned by IANA. Type: to be assigned by IANA.
Length: the total length of the value field not including Type and Length: the total length of the value field not including Type and
Length fields. Length fields.
Flags: 8 bits of flags. Following flags are defined: Flags: 8 bits of flags. Following flags are defined:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
| Reserved |G | | Reserved |L |
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
G-Flag: Global flag. Set when the Path Segment is global within an L-Flag: Local flag. Set when the Path Segment has local significance
SR domain. The rest bits of Flag are reserved and MUST be set to 0 on an SR node. The rest bits of Flag are reserved and MUST be set to
on transmission and MUST be ignored on receipt. 0 on transmission and MUST be ignored on receipt.
ST: Segment type, specifies the type of the Path Segment, and it has ST: Segment type, specifies the type of the Path Segment, and it has
following types: following types:
o 0: SR-MPLS Path Segment o 0: SR-MPLS Path Segment
o 1-255:Reserved o 1: SRv6 Path Segment
o 2-255:Reserved
Path Segment ID: The Path Segment ID of an SR path. The Path Segment Path Segment ID: The Path Segment ID of an SR path. The Path Segment
type is indicated by the Segment Type(ST) field. It can be a Path type is indicated by the Segment Type(ST) field. It can be a Path
Segment in SR-MPLS [I-D.ietf-spring-mpls-path-segment], or other IDs Segment in SR-MPLS [I-D.ietf-spring-mpls-path-segment], a Path
Segment in SRv6 [I-D.ietf-spring-srv6-path-segment], or other IDs
that identifies a path. When ST is 0, the Path Segment ID is a SR- that identifies a path. When ST is 0, the Path Segment ID is a SR-
MPLS Path Segment, and format is shown below. MPLS Path Segment, and format is shown below.
0 1 2 3 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 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 | Flags | ST=0 | | Type | Length | Flags | ST=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Segment Label | TC |S| TTL | | Path Segment Label | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. SR-MPLS Path Segment sub-TLV Figure 2. SR-MPLS Path Segment sub-TLV
When ST is 1, the Path Segment ID is a 128-bit SRv6 Path Segment.
4. SR Policy for Bidirectional Path 4. SR Policy for Bidirectional Path
In some scenarios, for example, mobile backhaul transport network, In some scenarios, for example, mobile backhaul transport network,
there are requirements to support bidirectional path. In SR, a there are requirements to support bidirectional path. In SR, a
bidirectional path can be represented as a binding of two bidirectional path can be represented as a binding of two
unidirectional SR paths. This document also defines a Reverse unidirectional SR paths. This document also defines a Reverse
Segment List sub-TLV to describe the reverse path associated with the Segment List sub-TLV to describe the reverse path associated with the
forward path specified by the Segment List. An SR policy carrying SR forward path specified by the Segment List. An SR policy carrying SR
bidirectional path information is expressed as below: bidirectional path information is expressed as below:
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6. IANA Considerations 6. IANA Considerations
This document defines new Sub-TLVs in following registries: This document defines new Sub-TLVs in following registries:
6.1. Existing Registry: BGP Tunnel Encapsulation Attribute sub-TLVs 6.1. Existing Registry: BGP Tunnel Encapsulation Attribute sub-TLVs
This document defines new sub-TLVs in the registry "SR Policy List This document defines new sub-TLVs in the registry "SR Policy List
Sub-TLVs" [I-D.ietf-idr-segment-routing-te-policy] to be assigned by Sub-TLVs" [I-D.ietf-idr-segment-routing-te-policy] to be assigned by
IANA: IANA:
Codepoint Description Reference Codepoint Description Reference
------------------------------------------------------------- -------------------------------------------------------------
TBA Path Segment sub-TLV This document TBA Path Segment sub-TLV This document
TBA Reverse Segment List sub-TLV This document TBA Reverse Segment List sub-TLV This document
7. Security Considerations 7. Security Considerations
TBA TBA
8. Contributors 8. Contributors
Mach(Guoyi) Chen Mach(Guoyi) Chen
Huawei Technologies Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd. Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095 Beijing 100095
China China
Email: Mach.chen@huawei.com Email: Mach.chen@huawei.com
Jie Dong Jie Dong
Huawei Technologies Huawei Technologies
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professional comments. professional comments.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-idr-segment-routing-te-policy] [I-D.ietf-idr-segment-routing-te-policy]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P.,
Rosen, E., Jain, D., and S. Lin, "Advertising Segment Rosen, E., Jain, D., and S. Lin, "Advertising Segment
Routing Policies in BGP", draft-ietf-idr-segment-routing- Routing Policies in BGP", draft-ietf-idr-segment-routing-
te-policy-09 (work in progress), May 2020. te-policy-11 (work in progress), November 2020.
[I-D.ietf-spring-mpls-path-segment] [I-D.ietf-spring-mpls-path-segment]
Cheng, W., Li, H., Chen, M., Gandhi, R., and R. Zigler, Cheng, W., Li, H., Chen, M., Gandhi, R., and R. Zigler,
"Path Segment in MPLS Based Segment Routing Network", "Path Segment in MPLS Based Segment Routing Network",
draft-ietf-spring-mpls-path-segment-03 (work in progress), draft-ietf-spring-mpls-path-segment-03 (work in progress),
September 2020. September 2020.
[I-D.ietf-spring-segment-routing-policy] [I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft- P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-09 (work in progress), ietf-spring-segment-routing-policy-09 (work in progress),
November 2020. November 2020.
[I-D.ietf-spring-srv6-path-segment]
Li, C., Cheng, W., Chen, M., Dhody, D., and R. Gandhi,
"Path Segment for SRv6 (Segment Routing in IPv6)", draft-
ietf-spring-srv6-path-segment-00 (work in progress),
November 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
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