Internet DRAFT - draft-ali-spring-ioam-srv6
draft-ali-spring-ioam-srv6
SPRING Working Group Z. Ali
Internet-Draft R. Gandhi
Intended status: Standards Track C. Filsfils
Expires: January 10, 2023 F. Brockners
N. Nainar
C. Pignataro
Cisco Systems, Inc.
C. Li
M. Chen
Huawei
G. Dawra
LinkedIn
July 10, 2022
Segment Routing Header encapsulation for In-situ OAM Data
draft-ali-spring-ioam-srv6-06
Abstract
OAM and PM information from the SR endpoints can be piggybacked in
the data packet. The OAM and PM information piggybacking in the data
packets is also known as In-situ OAM (IOAM). IOAM records
operational and telemetry information in the data packet while the
packet traverses a path between two points in the network. This
document defines how IOAM data fields are transported as part of the
Segment Routing with IPv6 data plane (SRv6) header.
Status of This Memo
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This Internet-Draft will expire on January 10, 2023.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirement Language . . . . . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
3. OAM Metadata Piggybacked in Data Packets . . . . . . . . .. . 4
3.1 IOAM Data Field Encapsulation in SRH . . . . . . . . . . . . 4
4. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Ingress Node . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. SR Segment Endpoint Node . . . . . . . . . . . . . . . . . 5
4.3. Egress Node . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
OAM and PM information from the SR endpoints can be piggybacked in
the data packet. The OAM and PM information piggybacking in the data
packets is also known as In-situ OAM (IOAM). IOAM records
OAM information within the packet while the packet traverses a
particular network domain. The term "in-situ" refers to the fact
that the IOAM data fields are added to the data packets rather than
being sent within probe packets specifically dedicated to OAM.
This document defines how IOAM data fields are transported as part of
the Segment Routing with IPv6 data plane (SRv6) header
[I-D.6man-segment-routing-header].
The IOAM data fields carried are defined in
[I-D.ietf-ippm-ioam-data], and can be used for various use-cases
including Performance Measurement (PM) and Proof-of-Transit (PoT).
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2. Conventions
2.1. Requirement 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 [RFC2119] [RFC8174]
when, and only when, they appear in all capitals, as shown here.
2.2. Abbreviations
Abbreviations used in this document:
IOAM In-situ Operations, Administration, and Maintenance
OAM Operations, Administration, and Maintenance
PM Performance Measurement
PoT Proof-of-Transit
SR Segment Routing
SRH SRv6 Header
SRv6 Segment Routing with IPv6 Data plane
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3. OAM Metadata Piggybacked in Data Packets
OAM and PM information from the SR endpoints can be piggybacked in
the data packet. The OAM and PM information piggybacking in the data
packets is also known as In-situ OAM (IOAM). This section describes
iOAM functionality in SRv6 network.
The IOAM data is carried in SRH.TLV. This enables the IOAM mechanism
to build on the network programmability capability of SRv6. Specifically,
the ability for an SRv6 endpoint to determine whether to
process or ignore some specific SRH TLVs is based on the SID
function. This enables collection of the IOAM information hardware friendly
based on the intermediate endpoint capability. The nodes that are not
capable of supporting the IOAM functionality does not have to look or
process SRH TLV (i.e., such nodes can simply ignore the SRH IOAM
TLV). This also enable collection of IOAM data only from segment endpoint.
3.1 IOAM Data Field Encapsulation in SRH
The SRv6 encapsulation header (SRH) is defined in [I-D.ietf-6man-
segment-routing-header]. IOAM data fields are carried in the SRH,
using a single pre-allocated SRH TLV. The different IOAM data fields
defined in [I-D.ietf-ippm-ioam-data] are added as sub-TLVs.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRH-TLV-Type | LEN | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| IOAM-Type | IOAM HDR LEN | RESERVED | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I
! | O
! | A
~ IOAM Option and Data Space ~ M
| | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| |
| |
| Payload + Padding (L2/L3/...) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IOAM data encapsulation in SRH
SRH-TLV-Type: IOAM TLV Type for SRH is defined as TBA1.
The fields related to the encapsulation of IOAM data fields in the
SRH are defined as follows:
IOAM-Type: 8-bit field defining the IOAM Option type, as defined in
Section 7.2 of [I-D.ietf-ippm-ioam-data].
IOAM HDR LEN: 8-bit unsigned integer. Length of the IOAM HDR in
4-octet units.
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RESERVED: 8-bit reserved field MUST be set to zero upon transmission
and ignored upon receipt.
IOAM Option and Data Space: IOAM option header and data is present
as defined by the IOAM-Type field, and is defined in Section 4 of
[I-D.ietf-ippm-ioam-data].
4. Procedure
This section summarizes the procedure for IOAM data encapsulation in
SRv6 SRH. The SR nodes implementing the IOAM functionality follows
the MTU and other considerations outlined in
[I-D.6man-extension-header-insertion].
4.1. Ingress Node
As part of the SRH encapsulation, the ingress node of an SR domain or
an SR Policy [I-D.ietf-spring-segment-routing-policy] MAY add the
IOAM TLV in the SRH of the data packet. If an ingress node supports
IOAM functionality and, based on a local configuration, wants to
collect IOAM data, it adds IOAM TLV in the SRH. Based on the size of
the segment list (SL), the ingress node preallocates space in the
IOAM TLV.
If IOAM data from the last node in the segment-list (Egress node) is
desired, the ingress uses an Ultimate Segment Pop (USP) SID
advertised by the Egress node.
The ingress node MAY also insert the IOAM data about the local
information in the IOAM TLV in the SRH at index 0 of the preallocated
IOAM TLV.
4.2. Intermediate SR Segment Endpoint Node
The SR segment endpoint node is any node receiving an IPv6 packet
where the destination address of that packet is a local SID. As part
of the SR Header processing as described in [I-D.ietf-6man-segment-
routing-header] and [I-D.ietf-spring-srv6-network-programming], the
SR Segment Endpoint node performs the following IOAM operations.
If an intermediate SR segment endpoint node is not capable of
processing IOAM TLV, it simply ignores it. I.e., it does not have to
look or process SRH TLV.
If an intermediate SR segment endpoint node is capable of processing
IOAM TLV and the local SID supports IOAM data recording, it checks if
any SRH TLV is present in the packet using procedures defined in [I-
D.ietf-6man-segment-routing-header]. If the node finds IOAM TLV in
the SRH it finds the local index at which it is expected to record
the IOAM data. The local index is found using the SRH.SL field. The
node records the IOAM data at the desired preallocated space.
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4.3. Egress Node
The Egress node is the last node in the segment-list of the SRH.
When IOAM data from the Egress node is desired, a USP SID advertised
by the Egress node is used by the Ingress node.
The processing of IOAM TLV at the Egress node is similar to the
processing of IOAM TLV at the SR Segment Endpoint Node. The only
difference is that the Egress node may telemeter the IOAM data to an
external entity.
5. IANA Considerations
IANA is requested to allocate a mutable SRH TLV Type for IOAM TLV data fields
under registry name "Segment Routing Header TLVs" requested by [I-
D.6man-segment-routing-header].
+--------------+--------------------------+---------------+
| SRH TLV Type | Description | Reference |
+--------------+--------------------------+---------------+
| TBA1 Greater | TLV for IOAM Data Fields | This document |
| than 128 | | |
+--------------+--------------------------+---------------+
6. Security Considerations
The security considerations of SRv6 are discussed in
[I-D.spring-srv6-network-programming] and
[I-D.6man-segment-routing-header], and the security considerations of
IOAM in general are discussed in [I-D.ietf-ippm-ioam-data].
IOAM is considered a "per domain" feature, where one or several
operators decide on leveraging and configuring IOAM according to
their needs. Still, operators need to properly secure the IOAM
domain to avoid malicious configuration and use, which could include
injecting malicious IOAM packets into a domain.
7. Acknowledgements
The authors would like to thank Shwetha Bhandari and Vengada Prasad
Govindan for the discussions on IOAM.
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8. References
8.1. 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.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", RFC 8174, May 2017.
[I-D.spring-srv6-network-programming] Filsfils, C. et al. "SRv6
Network Programming",
draft-filsfils-spring-srv6-network-programming, work in
progress.
[I-D.6man-segment-routing-header] Previdi, S., Filsfils, C. et al,
"IPv6 Segment Routing Header (SRH)",
draft-ietf-6man-segment-routing-header, work in progress.
[I-D.ietf-ippm-ioam-data] Brockners, F., Bhandari, S., Pignataro,
C., Gredler, H., Leddy, J., Youell, S., Mizrahi, T.,
Mozes, D., Lapukhov, P., Chang, R., and Bernier, D., "Data
Fields for In-situ OAM", draft-ietf-ippm-ioam-data, work
in progress.
[I-D.spring-segment-routing-policy] Filsfils, C., et al., "Segment
Routing Policy Architecture",
draft-ietf-spring-segment-routing-policy, work in
progress.
8.2. Informative References
[I-D.6man-extension-header-insertion] D. Voyer, et al., "Insertion
of IPv6 Segment Routing Headers in a Controlled Domain",
draft-voyer-6man-extension-header-insertion, work in
progress.
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Authors' Addresses
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
Rakesh Gandhi
Cisco Systems, Inc.
Canada
Email: rgandhi@cisco.com
Clarence Filsfils
Cisco Systems, Inc.
Belgium
Email: cf@cisco.com
Frank Brockners
Cisco Systems, Inc.
Germany
Email: fbrockne@cisco.com
Nagendra Kumar Nainar
Cisco Systems, Inc.
Email: naikumar@cisco.com
Carlos Pignataro
Cisco Systems, Inc.
Email: cpignata@cisco.com
Cheng Li
Huawei
Email: chengli13@huawei.com
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
Gaurav Dawra
LinkedIn
Email: gdawra.ietf@gmail.com
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