Encapsulation of Path Segment in SRv6
draft-li-6man-srv6-path-segment-encap-05
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| Authors | Cheng Li , Weiqiang Cheng , Yongqing Zhu , Zhenbin Li , Dhruv Dhody | ||
| Last updated | 2021-02-22 (Latest revision 2020-10-30) | ||
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draft-li-6man-srv6-path-segment-encap-05
6man Working Group C. Li
Internet-Draft Huawei Technologies
Intended status: Standards Track W. Cheng
Expires: August 26, 2021 China Mobile
Y. Zhu
China Telecom
Z. Li
D. Dhody
Huawei Technologies
February 22, 2021
Encapsulation of Path Segment in SRv6
draft-li-6man-srv6-path-segment-encap-05
Abstract
Segment Routing (SR) allows for a flexible definition of end-to-end
paths by encoding an ordered list of instructions, called "segments".
The SR architecture can be implemented over an IPv6 data plane,
called SRv6. In some use-cases such as end-to-end SR Path Protection
and Performance Measurement (PM), an SRv6 path needs to be
identified. This document defines the encoding of Path Segment in
SRv6 networks.
Status of This Memo
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This Internet-Draft will expire on August 26, 2021.
Copyright Notice
Copyright (c) 2021 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Encoding of an SRv6 Path Segment . . . . . . . . . . . . . . 3
2.1. Encapsulation of SRv6 Path Segment . . . . . . . . . . . 3
3. Processing of SRv6 Path Segment . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Segment routing (SR) [RFC8402] is a source routing paradigm that
explicitly indicates the forwarding path for packets at the ingress
node by inserting an ordered list of instructions, called segments.
When segment routing is deployed on an IPv6 data plane, it is called
SRv6, and it uses a new IPv6 [RFC8200] Routing Header (EH) called the
IPv6 Segment Routing Header (SRH) [RFC8754] to construct an SRv6
path. As per [I-D.ietf-spring-srv6-network-programming], an SRv6
segment identifier is a 128-bit value, which can be represented as
LOC:FUNCT, where LOC is the L most significant bits and FUNCT is the
128-L least significant bits. Most often the LOC part of the SID is
routable and leads to the node which instantiates that SID. The
FUNCT part of the SID is an opaque identification of a local function
bound to the SID.
In several use cases, such as binding bidirectional path
[I-D.ietf-pce-sr-bidir-path] and end-to-end performance measurement
[I-D.gandhi-spring-twamp-srpm], the ability to implement path
identification is a pre-requisite. In SRv6, it is possible to
identify a path by the content of the segment list. However, the
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segment list may not be a good key, since the length of the segment
list may be too long and flexible according to the number of SIDs.
Therefore, [I-D.ietf-spring-srv6-path-segment] defines an SRv6 Path
Segment to identify an SRv6 path.
This document defines the encoding of an SRv6 Path Segment in SRv6
networks.
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.
1.2. Terminology
PM: Performance Measurement.
SID: Segment ID.
SL: Segment List.
SR: Segment Routing.
SRH: Segment Routing Header.
PSID: Path Segment Identifier.
PSP: Penultimate Segment Popping.
Further, this document makes use of the terms defined in [RFC8402]
and [I-D.ietf-spring-srv6-network-programming].
2. Encoding of an SRv6 Path Segment
This section will describe the SRH encoding of an SRv6 Path Segment
as defined in [I-D.ietf-spring-srv6-path-segment]. As per
[I-D.ietf-spring-srv6-path-segment], an SRv6 Path Segment is a
128-bits value, which identifies an SRv6 path.
2.1. Encapsulation of SRv6 Path Segment
The SRv6 Path Segment MUST appear only once in a SID list, and it
MUST appear as the last entry.
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To indicate the existence of a Path Segment in the SRH, this document
defines a P-bit in the SRH flag field. The encapsulation of SRv6
Path Segment is shown below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type | Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Entry | Flags |P| Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Segment List[0] (128 bits IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
...
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Segment List[n-1] (128 bits IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SRv6 Path Segment (Segment List[n],128 bits IPv6 value) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// //
// Optional Type Length Value objects (variable) //
// //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. SRv6 Path Segment in SID List
o P-bit: set when SRv6 Path Segment is inserted. It MUST be ignored
when a node does not support SRv6 Path Segment processing.
3. Processing of SRv6 Path Segment
The processing of SRv6 path segment is out of the scope of this
document and is defined in [I-D.ietf-spring-srv6-path-segment].
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4. IANA Considerations
This document requests IANA to allocate bit position TBA within the
"Segment Routing Header Flags" registry defined in [RFC8402].
5. Security Considerations
TBA
6. Acknowledgements
TBA
7. References
7.1. Normative References
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-28 (work in
progress), December 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
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>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
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[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
7.2. Informative References
[I-D.gandhi-spring-twamp-srpm]
Gandhi, R., Filsfils, C., Voyer, D., Chen, M., and B.
Janssens, "Performance Measurement Using TWAMP Light for
Segment Routing Networks", draft-gandhi-spring-twamp-
srpm-11 (work in progress), October 2020.
[I-D.ietf-idr-sr-policy-path-segment]
Li, C., Li, Z., Chen, H., Cheng, W., and K. Talaulikar,
"SR Policy Extensions for Path Segment and Bidirectional
Path", draft-ietf-idr-sr-policy-path-segment-02 (work in
progress), November 2020.
[I-D.ietf-pce-sr-bidir-path]
Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong,
"Path Computation Element Communication Protocol (PCEP)
Extensions for Associated Bidirectional Segment Routing
(SR) Paths", draft-ietf-pce-sr-bidir-path-05 (work in
progress), January 2021.
[I-D.ietf-pce-sr-path-segment]
Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong,
"Path Computation Element Communication Protocol (PCEP)
Extension for Path Segment in Segment Routing (SR)",
draft-ietf-pce-sr-path-segment-02 (work in progress),
November 2020.
[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-09 (work in progress),
November 2020.
Authors' Addresses
Cheng Li
Huawei Technologies
Email: c.l@huawei.com
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Weiqiang Cheng
China Mobile
Email: chengweiqiang@chinamobile.com
Yongqing Zhu
China Telecom
Guangzhou
Email: zhuyq8@chinatelecom.cn
Zhenbin Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore 560066
India
Email: dhruv.ietf@gmail.com
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