Internet-Draft IPFIX Segment Routing over IPv6 May 2023
Graf, et al. Expires 26 November 2023 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-ietf-opsawg-ipfix-srv6-srh-14
Published:
Intended Status:
Standards Track
Expires:
Authors:
T. Graf
Swisscom
B. Claise
Huawei
P. Francois
INSA-Lyon

Export of Segment Routing over IPv6 Information in IP Flow Information Export (IPFIX)

Abstract

This document introduces new IP Flow Information Export (IPFIX) Information Elements to identify a set of Segment Routing over IPv6 (SRv6) related information such as data contained in a Segment Routing Header (SRH), the SRv6 control plane, and the SRv6 endpoint behavior that traffic is being forwarded with.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 26 November 2023.

Table of Contents

1. Introduction

A dedicated Routing Extension Header, called Segment Routing Header (SRH), is defined in [RFC8754] for use of Segment Routing (SR) over IPv6 data plane.

Also, three routing protocol extensions, OSPFv3 [I-D.ietf-lsr-ospfv3-srv6-extensions], IS-IS [RFC9352] and BGP Prefix Segment Identifiers(Prefix-SIDs) [RFC8669] and Path Computation Element Communication Protocol (PCEP) Extension [I-D.ietf-pce-segment-routing-ipv6] and Segment Routing Policy [RFC9256] are defined to propagate Segment Identifiers (SIDs).

SRv6 segment endpoint behaviors describe how packets should be processed by SRv6 Segment Endpoint Nodes. Such behaviors are defined in [RFC8986].

This document specifies eleven new IPFIX Information Elements (IEs) and one new subregistry within the "IPFIX Information Elements" registry [RFC7012], for SRv6 purposes.

These IEs are used to export the SRv6 active segment and its control plane protocol, the SRv6 Segment List, the next SRv6 node and its type, and the numbers of SRv6 segments left.

Some examples are provided in Appendix A.

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.

This document makes use of the terms defined in [RFC7011], [RFC8402] and [RFC8754].

The following terms are used as defined in [RFC7011]:

The following terms are used as defined in [RFC8402]:

The following terms are used as defined in [RFC8754]:

3. New IPFIX IPv6 SRH Information Elements

This section specifies the new IPFIX IPv6 SRH IEs.

srhFlagsIPv6
8-bit flags defined in the SRH (Section 2 of [RFC8754]).
srhTagIPv6
16-bit tag field defined in the SRH (Section 2 of [RFC8754]). A tag is used to mark a packet as part of a class or group of packets sharing the same set of properties.
srhSegmentIPv6
128-bit IPv6 address that represents a SRv6 segment.
srhActiveSegmentIPv6
128-bit IPv6 address that represents the active SRv6 segment.
srhSegmentIPv6BasicList
Ordered basicList [RFC6313] of zero or more 128-bit IPv6 addresses in the SRH that represents the SRv6 Segment List. As specified in Section 2 of [RFC8754], the Segment List is encoded starting from the last segment of the SR Policy. That is, the first element of the Segment List (Segment List[0]) contains the last segment of the SR Policy, the second element contains the penultimate segment of the SR Policy, and so on.
srhSegmentIPv6ListSection
The SRH Segment List as defined in Section 2 of [RFC8754] as a series of octets in IPFIX.
srhSegmentsIPv6Left
8-bit unsigned integer defining the number of segments remaining to reach the end of the Segment List from the SRH, as specified by the "Segments Left" field in Section 4.4 of [RFC8200] and mentioned part of the SRH in Section 2 of [RFC8754]).
srhIPv6Section
Exposes the SRH and its TLVs as specified in Section 2 of [RFC8754] as a series of octets in IPFIX.
srhIPv6ActiveSegmentType
Designator of the routing protocol or PCEP extension where the active SRv6 segment has been learned from.
srhSegmentIPv6LocatorLength
The SRH segment IPv6 locator length specified as the number of significant bits. Together with srhSegmentIPv6 it enables the calculation of the SRv6 Locator.
srhSegmentIPv6EndpointBehavior
16-bit unsigned integer that represents a SRv6 Endpoint behavior as per Section 4 of [RFC8986].

Note that the srhSegmentIPv6, srhSegmentIPv6LocatorLength, and srhSegmentIPv6EndpointBehavior IPFIX IEs are generic fields, to be used in the context of IPFIX Options Templates or IPFIX Structured Data [RFC6313].

4. Sample Use Cases

The IPFIX IEs srhSegmentIPv6BasicList (TBD5) or srhSegmentIPv6ListSection (TBD6), srhActiveSegmentIPv6 (TBD4), srhSegmentsIPv6Left (TBD7), srhIPv6ActiveSegmentType(TBD9), forwardingStatus (89) [RFC7270] [IANA-IPFIX], and some existing counter informations [IANA-IPFIX] providing answers to the following questions (amongst others):

5. IANA Considerations

Note to the RFC-Editor:

5.1. New IPFIX IPv6 SRH Information Elements

This document requests IANA to add new IEs (Section 5.1) to the "IPFIX Information Elements" registry [RFC7012] available at [IANA-IPFIX].

Table 1 lists the new IPv6 SRH IEs:


     +-------+--------------------------------+
     |Element|              Name              |
     |   ID  |                                |
     +-------+--------------------------------+
     | TBD1  | srhFlagsIPv6                   |
     |       |                                |
     +-------+--------------------------------+
     | TBD2  | srhTagIPv6                     |
     |       |                                |
     +-------+--------------------------------+
     | TBD3  | srhSegmentIPv6                 |
     |       |                                |
     +-------+--------------------------------+
     | TBD4  | srhActiveSegmentIPv6           |
     |       |                                |
     +-------+--------------------------------+
     | TBD5  | srhSegmentIPv6BasicList        |
     |       |                                |
     +-------+--------------------------------+
     | TBD6  | srhSegmentIPv6ListSection      |
     |       |                                |
     +-------+--------------------------------+
     | TBD7  | srhSegmentsIPv6Left            |
     |       |                                |
     +-------+--------------------------------+
     | TBD8  | srhIPv6Section                 |
     |       |                                |
     +-------+--------------------------------+
     | TBD9  | srhIPv6ActiveSegmentType       |
     |       |                                |
     +-------+--------------------------------+
     | TBD10 | srhSegmentIPv6LocatorLength    |
     |       |                                |
     +-------+--------------------------------+
     | TBD11 | srhSegmentIPv6EndpointBehavior |
     |       |                                |
     +-------+--------------------------------+

  Table 1: New IPv6 SRH IEs in the "IPFIX Information Elements" Registry

5.1.1. srhFlagsIPv6

Name:
srhFlagsIPv6
ElementID:
TBD1
Description:
The 8-bit flags defined in the SRH (Section 2 of [RFC8754]). Assigned flags and their meanings are provided in the "Segment Routing Header Flags" IANA registry.
Abstract Data Type:
unsigned8
Data Type Semantics:
flags
Additional Information:
See the assignments in the "Segment Routing Header Flags" IANA registry at https://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xhtml#segment-routing-header-flags. See also RFC8754 for the SRH specification.
Reference:
[RFC-to-be]

5.1.2. srhTagIPv6

Name:
srhTagIPv6
ElementID:
TBD2
Description:
The 16-bit tag field defined in the SRH (Section 2 of [RFC8754]). A tag is used to mark a packet as part of a class or group of packets sharing the same set of properties.
Abstract Data Type:
unsigned16
Data Type Semantics:
identifier
Additional Information:
See Section 2 of [RFC8754] for more details about the tag.
Reference:
[RFC-to-be]

5.1.3. srhSegmentIPv6

Name:
srhSegmentIPv6
ElementID:
TBD3
Description:
The 128-bit IPv6 address that represents a SRv6 segment.
Abstract Data Type:
ipv6address
Data Type Semantics:
default
Additional Information:
Specified in Section 1 of [RFC8402] and mentioned in "Segment List" in Section 2 of [RFC8754].
Reference:
[RFC-to-be]

5.1.4. srhActiveSegmentIPv6

Name:
srhActiveSegmentIPv6
ElementID:
TBD4
Description:
The 128-bit IPv6 address that represents the active SRv6 segment.
Abstract Data Type:
ipv6address
Data Type Semantics:
default
Additional Information:
See Section 2 of [RFC8402] for the definition of active segment.
Reference:
[RFC-to-be]

5.1.5. srhSegmentIPv6BasicList

Name:
srhSegmentIPv6BasicList
ElementID:
TBD5
Description:
The Ordered basicList [RFC6313] of zero or more 128-bit IPv6 addresses in the SRH that represents the SRv6 Segment List. As specified in Section 2 of [RFC8754], the Segment List is encoded starting from the last segment of the SR Policy. That is, the first element of the Segment List (Segment List[0]) contains the last segment of the SR Policy, the second element contains the penultimate segment of the SR Policy, and so on.
Abstract Data Type:
basicList
Data Type Semantics:
list
Additional Information:
See Section 2 of [RFC8754] for more details about the SRv6 Segment List.
Reference:
[RFC-to-be]

5.1.6. srhSegmentIPv6ListSection

Name:
srhSegmentIPv6ListSection
ElementID:
TBD6
Description:
The SRH Segment List as defined in Section 2 of [RFC8754] as a series of octets in IPFIX.
Abstract Data Type:
octetArray
Data Type Semantics:
default
Additional Information:
See Section 2 of [RFC8754] for more details about the SRv6 Segment List.
Reference:
[RFC-to-be]

5.1.7. srhSegmentsIPv6Left

Name:
srhSegmentsIPv6Left
ElementID:
TBD7
Description:
8-bit unsigned integer defining the number of segments remaining to reach the end of the Segment List in the SRH.
Abstract Data Type:
unsigned8
Data Type Semantics:
quantity
Additional Information:
Specified by the "Segments Left" field in Section 4.4 of [RFC8200] and mentioned in Section 2 of [RFC8754]).
Reference:
[RFC-to-be]

5.1.8. srhIPv6Section

Name:
srhIPv6Section
Description:
The SRH and its TLVs as defined in Section 2 of [RFC8754] as a series of octets in IPFIX.
Abstract Data Type:
octetArray
Data Type Semantics:
default
Additional Information:
See Section 2 of [RFC8754] for more details about the structure of an SRH.
Reference:
[RFC-to-be]

5.1.9. srhIPv6ActiveSegmentType

Name:
srhIPv6ActiveSegmentType
ElementID:
TBD9
Description:
The designator of the routing protocol or PCEP extension from where the active SRv6 segment has been learned from. Values for this Information Element are listed in the "IPFIX IPv6 SRH Segment type" subregistry, see [IANA-IPFIX].
Abstract Data Type:
unsigned8
Data Type Semantics:
identifier
Additional Information:
See the assigned types in [IPFIX IPv6 SRH Segment Type Subregistry].
Note to IANA:
Please replace [IPFIX IPv6 SRH Segment Type Subregistry] with the URL of the IANA subregistry.
Reference:
[RFC-to-be]

5.1.10. srhSegmentIPv6LocatorLength

Name:
srhSegmentIPv6LocatorLength
ElementID:
TBD10
Description:
The SRH segment IPv6 locator length specified as the number of significant bits. Together with srhSegmentIPv6 it enables the calculation of the SRv6 Locator.
Abstract Data Type:
unsigned8
Data Type Semantics:
default
Additional Information:
See Section 3.1 of [RFC8986] for more details about the SID format.
Reference:
[RFC-to-be]

5.1.11. srhSegmentIPv6EndpointBehavior

Name:
srhSegmentIPv6EndpointBehavior
ElementID:
TBD11
Description:
The 16-bit unsigned integer that represents a SRv6 Endpoint behavior as per Section 4 of [RFC8986]. Assigned values and their meanings are provided in the "SRV6 Endpoint Behavior" registry.
Abstract Data Type:
unsigned16
Data Type Semantics:
identifier
Additional Information:
See the assigned behaviors at the "SRv6 Endpoint Behavior" registry available at https://www.iana.org/assignments/segment-routing/segment-routing.xhtml#srv6-endpoint-behaviors. See Section 4 of [RFC8986] for more details about the endpoint behaviors processing.
Reference:
[RFC-to-be]

5.2. New IPFIX IPv6 SRH Segment Type Subregistry

This document requests IANA to create a new subregistry called "IPFIX IPv6 SRH Segment Type" under the "IPFIX Information Elements" registry [RFC7012] available at [IANA-IPFIX].

The allocation policy of this new subregistry is Expert Review (Section 4.5 of [RFC8126]).

The designated experts for this registry should be familiar with SRH. The guidelines that are being followed by the designated experts for the IPFIX registry should be followed for this subregistry. In particular, criteria that should be applied by the designated experts include determining whether the proposed registration duplicates existing entries and whether the registration description is clear and fits the purpose of this registry. Within the review period, the designated experts will either approve or deny the registration request, communicating this decision to IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful.

Initial values in the registry are defined in Table 2.



+-------+--------------------+---------------------------------------+
| Value |     Description    |        Additional Information         |
+-------+--------------------+---------------------------------------+
| TBD12 | Unknown            | [RFC-to-be]                           |
|       |                    |                                       |
+-------+--------------------+---------------------------------------+
| TBD13 | Segment Routing    | [RFC-to-be],                          |
|       | Policy             | <xref target="RFC9256"/>              |
+-------+--------------------+---------------------------------------+
| TBD14 | Path Computation   | [RFC-to-be],<xref target="            |
|       | Element            | I-D.ietf-pce-segment-routing-ipv6"/>  |
+-------+--------------------+---------------------------------------+
| TBD15 | OSPFv3             | [RFC-to-be],<xref target="            |
|       | Segment Routing    | I-D.ietf-lsr-ospfv3-srv6-extensions"/>|
+-------+--------------------+---------------------------------------+
| TBD16 | IS-IS              | [RFC-to-be],<xref target="RFC9352"/>  |
|       | Segment Routing    |                                       |
+-------+--------------------+---------------------------------------+
| TBD17 | BGP Segment        | [RFC-to-be],                          |
|       | Routing Prefix-SID | <xref target="RFC8669"/>              |
+-------+--------------------+---------------------------------------+

        Table 2: "IPFIX IPv6 SRH Segment Type" Subregistry

6. Operational Considerations

6.1. SRv6 Segment List

The zero or more 128-bit IPv6 addresses in the SRH [RFC8754] can be exported in two different ways, with two different IPFIX IEs:

  • srhSegmentIPv6BasicList
  • srhSegmentIPv6ListSection

The srhSegmentIPv6BasicList encodes the SRv6 Segment List with a basicList, specified in the IPFIX Structured Data [RFC6313]. This encoding offers the advantage to the data collection that the different IPv6 addresses are already structured as a list, without the need of post-processing. However, this method requires some extra processing on the exporter, to realize the BasicList data mapping.

The srhSegmentIPv6ListSection, on the other hand, encodes the list of IPv6 addresses as an octetArray. This doesn't impose any data flow manipulation on the exporter, facilitating the immediate export. However, the data collection MUST be able to decode the IPv6 addresses according to the SR specifications. Compared to the srhSegmentIPv6BasicList, the srhSegmentIPv6ListSection flow records length is slightly reduced.

It is not expected that an exporter would support both srhSegmentIPv6BasicList and srhSegmentIPv6ListSection at the same time.

6.2. Compressed SRv6 Segment List Decomposition

The SRv6 Segment List in the IPFIX IEs srhSegmentIPv6BasicList, srhSegmentIPv6ListSection and destinationIPv6Address could contain compressed-SID containers as described in [I-D.ietf-spring-srv6-srh-compression]. The SR Endpoint Flavors, described in Section 4 of [I-D.ietf-spring-srv6-srh-compression] defines new flavors for SID endpoint behaviors, and determine wherever the Segment List encoding is compressed, along with the flavor. The SID Locator as described in Section 3.1 of [RFC8986], determines the common most significant bits. By using described information from srhSegmentIPv6EndpointBehavior and srhSegmentIPv6LocatorLength the compressed-SID containers can be decoded at the data collection.

7. Acknowledgements

The authors would like to thank Yao Liu, Eduard Vasilenko, Bruno Decraene, Mohamed Boucadair, Kamran Raza, Qin Wu, Jim Guichard, Tero Kivinen, Paul Aitken, Roman Danyliw, John Scudder, Eric Vyncke, Erik Kline, Lars Eggert and Andrew Alston for their review and valuable comments, and Paolo Lucente and Alex Huang Feng for the implementation and validation.

8. Implementation Status

Note to the RFC-Editor: Please remove this section before publishing.

8.1. FD.io VPP

INSA Lyon implemented the following IEs as part of a prototype in the FD.io VPP (Vector Packet Processing) platform:

  • srhActiveSegmentIPv6
  • srhSegmentIPv6EndpointBehavior
  • srhSegmentsIPv6Left
  • srhFlagsIPv6
  • srhTagIPv6
  • srhSegmentIPv6ListSection
  • srhSegmentIPv6BasicList

The open source code can be obtained here: [INSA-Lyon-VPP] and was validated at the IETF 115 hackathon.

8.2. Huawei VRP

Huawei implemented the following IEs as part of a production implementation in the VRP platform:

  • srhActiveSegmentIPv6
  • srhSegmentsIPv6Left
  • srhFlagsIPv6
  • srhTagIPv6
  • srhSegmentIPv6ListSection

The implementation was validated at the IETF 115 hackathon.

8.3. Pmacct Data Collection

Paolo Lucente implemented the decomposition of the IE srhSegmentIPv6ListSection as part of a a production implementation in the open source Network Telemetry data collection project pmacct.

The source code can be obtained here: [Paolo-Lucente-Pmacct] and was validated at the IETF 115 hackathon.

9. Security Considerations

There exists no extra security considerations regarding allocation of these new IPFIX IEs compared to [RFC7012].

The IEs described in this document export provider plane data metrics on how packets are being forwarded within a SRv6 network. Applications and operators using the IEs described in this document must evaluate the sensitivity of this information in their implementation context, and apply the data-at-rest storage guidance in Section 11.8 of [RFC7011] as appropriate.

10. References

10.1. Normative References

[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC6313]
Claise, B., Dhandapani, G., Aitken, P., and S. Yates, "Export of Structured Data in IP Flow Information Export (IPFIX)", RFC 6313, DOI 10.17487/RFC6313, , <https://www.rfc-editor.org/info/rfc6313>.
[RFC7011]
Claise, B., Ed., Trammell, B., Ed., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, , <https://www.rfc-editor.org/info/rfc7011>.
[RFC7012]
Claise, B., Ed. and B. Trammell, Ed., "Information Model for IP Flow Information Export (IPFIX)", RFC 7012, DOI 10.17487/RFC7012, , <https://www.rfc-editor.org/info/rfc7012>.
[RFC8126]
Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, , <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <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, , <https://www.rfc-editor.org/info/rfc8200>.
[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, , <https://www.rfc-editor.org/info/rfc8754>.

10.2. Informative References

[I-D.ietf-lsr-ospfv3-srv6-extensions]
Li, Z., Hu, Z., Talaulikar, K., and P. Psenak, "OSPFv3 Extensions for SRv6", Work in Progress, Internet-Draft, draft-ietf-lsr-ospfv3-srv6-extensions-11, , <https://datatracker.ietf.org/doc/html/draft-ietf-lsr-ospfv3-srv6-extensions-11>.
[I-D.ietf-pce-segment-routing-ipv6]
Li, C., Negi, M. S., Sivabalan, S., Koldychev, M., Kaladharan, P., and Y. Zhu, "Path Computation Element Communication Protocol (PCEP) Extensions for Segment Routing leveraging the IPv6 dataplane", Work in Progress, Internet-Draft, draft-ietf-pce-segment-routing-ipv6-16, , <https://datatracker.ietf.org/doc/html/draft-ietf-pce-segment-routing-ipv6-16>.
[I-D.ietf-spring-srv6-srh-compression]
Cheng, W., Filsfils, C., Li, Z., Decraene, B., and F. Clad, "Compressed SRv6 Segment List Encoding in SRH", Work in Progress, Internet-Draft, draft-ietf-spring-srv6-srh-compression-04, , <https://datatracker.ietf.org/doc/html/draft-ietf-spring-srv6-srh-compression-04>.
[IANA-IPFIX]
"IANA, "IP Flow Information Export (IPFIX) Entities"", <https://www.iana.org/assignments/ipfix/ipfix.xhtml>.
[INSA-Lyon-VPP]
"INSA Lyon, FD.io VPP implementation", <https://github.com/network-analytics/vpp-srh-onpath-telemetry>.
[Paolo-Lucente-Pmacct]
"Paolo Lucente, Pmacct open source Network Telemetry Data Collection", <https://github.com/pmacct/pmacct>.
[RFC7270]
Yourtchenko, A., Aitken, P., and B. Claise, "Cisco-Specific Information Elements Reused in IP Flow Information Export (IPFIX)", RFC 7270, DOI 10.17487/RFC7270, , <https://www.rfc-editor.org/info/rfc7270>.
[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, , <https://www.rfc-editor.org/info/rfc8402>.
[RFC8669]
Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah, A., and H. Gredler, "Segment Routing Prefix Segment Identifier Extensions for BGP", RFC 8669, DOI 10.17487/RFC8669, , <https://www.rfc-editor.org/info/rfc8669>.
[RFC8986]
Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 (SRv6) Network Programming", RFC 8986, DOI 10.17487/RFC8986, , <https://www.rfc-editor.org/info/rfc8986>.
[RFC9256]
Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", RFC 9256, DOI 10.17487/RFC9256, , <https://www.rfc-editor.org/info/rfc9256>.
[RFC9352]
Psenak, P., Ed., Filsfils, C., Bashandy, A., Decraene, B., and Z. Hu, "IS-IS Extensions to Support Segment Routing over the IPv6 Data Plane", RFC 9352, DOI 10.17487/RFC9352, , <https://www.rfc-editor.org/info/rfc9352>.

Appendix A. IPFIX Encoding Examples

This appendix represents three different encodings for the newly introduced IEs, for the example values in Table 3. The three different encodings use the following IEs, respectively: srhSegmentIPv6BasicList, srhSegmentIPv6ListSection, and srhIPv6Section.


   +-----+------+-----+----------------+--------------------------|
   | SRH | SRH  | SRH | Active Segment |       Segment List       |
   | Nr  | Flags| Tag | Type           |                          |
   +-----+------+-----+----------------+--------------------------+
   | 1   | 0    | 123 | IS-IS          | 2001:db8::1, 2001:db8::2,|
   |     |      |     |                | 2001:db8::3              |
   +-----+------+-----+----------------+--------------------------+
   | 2   | 0    | 456 | IS-IS          | 2001:db8::4, 2001:db8::5 |
   +-----+------+-----+----------------+--------------------------+
   | 3   | 0    | 789 | IS-IS          | 2001:db8::6              |
   +-----+------+-----+----------------+--------------------------+

     Table 3: Three Observed SRH headers and Their Associated Routing Protocol

A.1. Three Observed SRH Headers and their Routing Protocol

A.1.1. Template Record and Data Set with Segment Basic List

With encoding in Figure 1, the examples in Table 3 are represented with the following IEs: “=>” is used to indicate which IE is mapped to a given information.

  • SR Flags => srhFlagsIPv6 (TBD1)
  • SR Tag => srhTagIPv6 (TBD2)
  • Active Segment Type => srhIPv6ActiveSegmentType (TBD9)
  • Segment List => srhSegmentIPv6BasicList (TBD5)

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          SET ID = 2           |       Length = 24             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Template ID = 256        |      Field Count = 4          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     srhFlagsIPv6 = TBD1     |      Field Length = 1         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|      srhTagIPv6 = TBD2      |      Field Length = 2         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|srhActiveSegmentIPv... = TBD9|      Field Length = 1         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|srhSegmentIPv6BasicList= TBD5|      Field Length = 0xFFFF    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 1: Template Record with Basic List Encoding Format

In this example, the Template ID is 256, which will be used in the Data Record. The field length for srhSegmentIPv6BasicList is 0xFFFF, which means the length of this IE is variable, and the actual length of this IE is indicated by the List Length field in the basicList format as per [RFC6313].

The data set is represented 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         SET ID = 256          |           Length = 136        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | srhFlagsIPv6  |        srhTagIPv6 = 123       | srhActiveSegme|
   | = 0           |                               | ntIPv...=TBD16|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      255      |        List Length = 53       |semantic=      |
   |               |                               |ordered        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     srhSegmentIPv6 = TBD3     |        Field Length = 16      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Segment List[0] = 2001:db8::1                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Segment List[1] = 2001:db8::2                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Segment List[2] = 2001:db8::3                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | srhFlagsIPv6  |        srhTagIPv6 = 456       | srhActiveSegme|
   | = 0           |                               | ntIPv...=TBD16|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      255      |        List Length = 37       |semantic=      |
   |               |                               |ordered        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     srhSegmentIPv6 = TBD3     |        Field Length = 16      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Segment List[0] = 2001:db8::4                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Segment List[1] = 2001:db8::5  (16 bytes)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | srhFlagsIPv6  |        srhTagIPv6 = 789       | srhActiveSegme|
   | = 0           |                               | ntIPv...=TBD16|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      255      |        List Length = 21       |semantic=      |
   |               |                               |ordered        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     srhSegmentIPv6 = TBD3     |        Field Length = 16      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Segment List[0] = 2001:db8::6  ...                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 2: Data Set Encoding Format for Basic List

A.1.2. Template Record and Data Set with Segment List Section

With encoding in Figure 3, the examples in Table 3 are represented with the following IEs: “=>” is used to indicate which IE is mapped to a given information.

  • SR Flags => srhFlagsIPv6 (TBD1)
  • SR Tag => srhTagIPv6 (TBD2)
  • Active Segment Type => srhIPv6ActiveSegmentType (TBD9)
  • Segment List => srhSegmentIPv6ListSection (TBD6)

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          SET ID = 2           |       Length = 24             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Template ID = 257        |      Field Count = 4          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     srhFlagsIPv6 = TBD1     |      Field Length = 1         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|      srhTagIPv6 = TBD2      |      Field Length = 2         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|srhActiveSegmentIPv... = TBD9|      Field Length = 1         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     srhSegmentIPv6List      |      Field Length = 0xFFFF    |
   | |     Section=TBD6            |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 3: Template Record with Segment List Section Encoding Format

In this example, the Template ID is 257, which will be used in the Data Record. The field length for srhSegmentIPv6ListSection in the Template Record is 0xFFFF, which means that the length of this IE is variable: its actual length is encoded in the Data Set. Note that, with an actual length inferior to 255 in the Data Record example, the length field is encoded in 8 bits (Section 7 of [RFC7011]).

The data can be represented 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         SET ID = 257          |           Length = 116        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | srhFlagsIPv6  |        srhTagIPv6 = 123       | srhActiveSegme|
   | = 0           |                               | ntIPv...=TBD16|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Length = 48   |   2001:db8::1                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      ...      |   2001:db8::2                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      ...      |   2001:db8::3                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      ...      | srhFlagsIPv6  |        srhTagIPv6 = 456       |
   |               | = 0           |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | srhActiveSegme| Length = 32   |   2001:db8::4                 |
   | ntIPv...=TBD15|               |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      ...                      |   2001:db8::5                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      ...                      |srhFlagsIPv6=0 | srhTagIPv6... |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | = 789         |         srhActiveSegment      | Length = 16   |
   |               |         IPv6Type=TBD16        |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        2001:db8::6 ...                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


     Figure 4: Data Set Encoding Format for Segment List Section

A.1.3. Template Record and Data Set with SRH Section

With encoding in Figure 5, the examples in Table 3 are represented with the following IEs: “=>” is used to indicate which IE is mapped to a given information.

  • SR Flags + SR Tag + Segment List => srhIPv6Section (TBD8)
  • Active Segment Type => srhIPv6ActiveSegmentType (TBD9)

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          SET ID = 2           |       Length = 16             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Template ID = 258        |      Field Count = 2          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| srhActiveSegmentIP... = TBD9|      Field Length = 1         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    srhIPv6Section = TBD8    |      Field Length = 0xFFFF    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 5: Template Record with SRH Section Encoding Format

In this example, the Template ID is 258, which will be used in the Data Record. The field length for srhIPv6Section in the Template Record is 0xFFFF, which means that the length of this IE is variable: its actual length is encoded in the Data Set. Note that, with an actual length inferior to 255 in the Data Record example, the length field is encoded in 8 bits (Section 7 of [RFC7011]).

The data can be represented 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         SET ID = 258          |           Length = (*)        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        srhIPv6ActiveSegmentType = TBD16       |  Length = (*) |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Next Header   |  Hdr Ext Len  | Routing Type  | Segments Left |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Last Entry   |     Flags     |              Tag              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Segment List[0] 2001:db8::1                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Segment List[1] 2001:db8::2                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Segment List[2] 2001:db8::3                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~          Optional Type Length Value objects (variable)        ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        srhIPv6ActiveSegmentType = TBD16       |    0xFFFF     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Next Header   |  Hdr Ext Len  | Routing Type  | Segments Left |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Last Entry   |     Flags     |              Tag              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Segment List[0] 2001:db8::4                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Segment List[1] 2001:db8::5                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~          Optional Type Length Value objects (variable)        ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        srhIPv6ActiveSegmentType = TBD16       |    0xFFFF     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Next Header   |  Hdr Ext Len  | Routing Type  | Segments Left |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Last Entry   |     Flags     |              Tag              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Segment List[0] 2001:db8::6                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~          Optional Type Length Value objects (variable)        ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 6: Data Set Encoding Format for SRH Section

(*) The Length must be calculated to include the optional Type Length Value objects.

A.2. Options Template Record and Data Set for SRv6 Segment End Point behavior and Locator Length

This appendix provides an SRv6 EndPoint Bevahior Options Template example, for the values presented in Table 4. In the Options Template case, the srhActiveSegmentIPv6 Information Element is a Scope field


   +-------+-------------+-------------------------+----------------+
   | Entry | SRH End     | SRH End                 | SRH Segment    |
   | Nr    | Point IPv6  | Point Behavior          | Locator Length |
   +-------+-------------+-------------------------+----------------+
   | 1     | 2001:db8::1 | End [1]                 | 48             |
   +-------+-------------+-------------------------+----------------+
   | 2     | 2001:db8::4 | End with NEXT-CSID [43] | 48             |
   +-------+-------------+-------------------------+----------------+
   | 3     | 2001:db8::6 | End.DX6 [16]            | 48             |
   +-------+-------------+-------------------------+----------------+

     Table 4: Three Observed SRv6 Segment End Point Behaviors
      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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 3            |          Length = 24          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID 259         |        Field Count = 3        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Scope Field Count = 1     |0| srhActiveSegmentIPv6 = TBD4 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Scope 1 Field Length = 4    |0|srhSegmentEndpointBeh..=TBD11|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 1        |0|srhSegmentIPv6Lo.Length=TBD10|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 4        |           Padding             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


       Figure 7: Template Record with SRH Section Encoding Format

In this example, the Template ID is 259, which will be used in the Data Record.

The data set is represented 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         SET ID = 259          |           Length = 28         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         2001:db8::1                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             End [1]           |               48              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        2001:db8::4                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    End with NEXT-CSID [43]    |               48              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         2001:db8::6                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             End.DX6 [16]      |               48              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


           Figure 8: Data Set Encoding Format for SRH Section

(*) The Length must be calculated to include the optional Type Length Value objects.

Authors' Addresses

Thomas Graf
Swisscom
Binzring 17
CH-8045 Zurich
Switzerland
Benoit Claise
Huawei
Pierre Francois
INSA-Lyon
Lyon
France