Internet-Draft IPFIX Segment Routing over IPv6 March 2023
Graf, et al. Expires 14 September 2023 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-ietf-opsawg-ipfix-srv6-srh-07
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 14 September 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 [I-D.ietf-lsr-isis-srv6-extensions] and BGP Prefix Segment Identifiers(Prefix-SIDs) [RFC9252] 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 are defined in [RFC8986] and describe how packets should be processed by SRv6 Segment Endpoint Nodes.

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 SRv6 active segment and its control plane protocol, the SRv6 segment list, the next SRv6 node and its type, and then 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. IPFIX Information Elements

This section specifies the new SRv6 IPFIX 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 an 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
Exposes the SRH Segment List as defined in Section 2 of [RFC8754] as series of n octets in IPFIX.
srhSegmentsIPv6Left
8-bit unsigned integer defining the number of segments remaining to reach the end of the segment list as defined in Section 2 of [RFC8754].
srhIPv6Section
Exposes the SRH and its TLVs as specified in Section 2 of [RFC8754] as series of n octets in IPFIX.
srhIPv6ActiveSegmentType
Name of the routing protocol or PCEP extension from where the active SRv6 segment has been learned from.
srhSegmentIPv6LocatorLength
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 counters information [IANA-IPFIX] allow to provide answers to the following questions (amongst others):

5. IANA Considerations

This document requests IANA to create new IEs (see table 1) and one new subregistry called "IPFIX IPv6 SRH Segment Type" (table 2) under the "IPFIX Information Elements" registry [RFC7012] available at [IANA-IPFIX].


     +-------+--------------------------------+
     |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 IEs in the "IPFIX Information Elements" registry

Note to the RFC-Editor:

5.1. srhFlagsIPv6

Name:
srhFlagsIPv6
ElementID:
TBD1
Description:
The 8-bit flags defined in the SRH. 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:
RFC8754. 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
Reference:
[RFC-to-be]

5.2. srhTagIPv6

Name:
srhTagIPv6
ElementID:
TBD2
Description:
The 16-bit tag field defined in the SRH that marks 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:
RFC8754
Reference:
[RFC-to-be]

5.3. srhSegmentIPv6

Name:
srhSegmentIPv6
ElementID:
TBD3
Description:
The 128-bit IPv6 address that represents an SRv6 segment.
Abstract Data Type:
ipv6address
Data Type Semantics:
default
Additional Information:
RFC8754
Reference:
[RFC-to-be]

5.4. 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:
RFC8754
Reference:
[RFC-to-be]

5.5. 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 described 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:
RFC8754
Reference:
[RFC-to-be]

5.6. srhSegmentIPv6ListSection

Name:
srhSegmentIPv6ListSection
ElementID:
TBD6
Description:
The SRH Segment List as defined in section 2 of [RFC8754] as series of n octets.
Abstract Data Type:
octetArray
Data Type Semantics:
default
Additional Information:
RFC8754
Reference:
[RFC-to-be]

5.7. srhSegmentsIPv6Left

Name:
srhSegmentsIPv6Left
ElementID:
TBD7
Description:
The 8-bit unsigned integer defining the number of route segments remaining to reach the end of the segment list as defined in Section 2 of [RFC8754].
Abstract Data Type:
unsigned8
Data Type Semantics:
quantity
Additional Information:
RFC8754
Reference:
[RFC-to-be]

5.8. srhIPv6Section

Name:
srhIPv6Section
Description:
The SRH and its TLVs as defined in Section 2 of [RFC8754] as series of n octets.
Abstract Data Type:
octetArray
Data Type Semantics:
default
Additional Information:
RFC8754
Reference:
[RFC-to-be]

5.9. srhIPv6ActiveSegmentType

Name:
srhIPv6ActiveSegmentType
ElementID:
TBD9
Description:
The name 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:
[IPFIX IPv6 SRH Segment Type Subregistry]
Note to IANA:
replace [IPFIX IPv6 SRH Segment Type Subregistry] with the URL
Reference:
[RFC-to-be]

5.9.1. IPFIX IPv6 SRH Segment Type Subregistry

Initial values in the registry are defined by the table below. New assignments of values will be administered by IANA and are subject to Expert Review [RFC8126]. Experts need to check definitions of new values for completeness, accuracy, and redundancy.



+-------+--------------------+---------------------------------------+
| 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="            |
|       | Segment Routing    | I-D.ietf-lsr-isis-srv6-extensions"/>  |
+-------+--------------------+---------------------------------------+
| TBD17 | BGP Segment        | [RFC-to-be],                          |
|       | Routing Prefix-SID | <xref target="RFC9252"/>              |
+-------+--------------------+---------------------------------------+

        Table 2: "IPFIX IPv6 SRH Segment type" subregistry

5.10. srhSegmentIPv6LocatorLength

Name:
srhSegmentIPv6LocatorLength
ElementID:
TBD10
Description:
The number of significant bits and together with srhSegmentIPv6 enables the calculation of the SRv6 Locator.
Abstract Data Type:
unsigned8
Data Type Semantics:
default
Additional Information:
Section 3.1 of RFC8986
Reference:
[RFC-to-be]

5.11. srhSegmentIPv6EndpointBehavior

Name:
srhSegmentIPv6EndpointBehavior
ElementID:
TBD11
Description:
The 16-bit SRv6 Endpoint behavior. Assigned values and their meanings are provided in the "SRV6 Endpoint Behavior" IANA registry [IANA-IPFIX].
Abstract Data Type:
unsigned16
Data Type Semantics:
identifier
Additional Information:
Section 4 of RFC8986. See the assignments in the "SRV6 Endpoint Behavior" IANA registry at https://www.iana.org/assignments/segment-routing/segment-routing.xhtml#srv6-endpoint-behaviors
Reference:
[RFC-to-be]

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 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 and srhSegmentIPv6ListSection could contain compressed-SID containers as described in [I-D.ietf-spring-srv6-srh-compression]. The SID endpoint behaviors described in section 4 of [I-D.ietf-spring-srv6-srh-compression] determine wherever the segment list is compressed or not. The SID Locator as described in Section 3.1 of [RFC8986], determines the common most significant bits.

6.3. Multiple Segment Routing Headers

If multiple SRHs are observed (for reasons that are not detailed here), the export of the same IE multiple times in one data record and related template record is supported and the order within the packet SHOULD be preserved in the IPFIX export according to Section 8 of [RFC7011]. If the network node is not capable to export IPFIX for more than one SRH, it MUST export IPFIX for the SRH of the active segment.

7. Implementation Status

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

7.1. 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.

7.2. Huawei VRP

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

  • srhActiveSegmentIPv6
  • srhSegmentsIPv6Left
  • srhFlagsIPv6
  • srhTagIPv6
  • srhSegmentIPv6ListSection

The implementation was validated at the IETF 115 hackathon.

7.3. Pmacct Data Collection

Paolo Lucente implemented the IE srhSegmentIPv6ListSection decomposition 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.

8. Acknowledgements

The authors would like to thank Yao Liu, Eduard Vasilenko, Bruno Decraene, Mohamed Boucadair, Kamran Raza and Qin Wu for their review and valuable comments, and Paolo Lucente and Alex Huang Feng for the implementation and validation.

9. Security Considerations

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

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>.
[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-isis-srv6-extensions]
Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and Z. Hu, "IS-IS Extensions to Support Segment Routing over IPv6 Dataplane", Work in Progress, Internet-Draft, draft-ietf-lsr-isis-srv6-extensions-19, , <https://datatracker.ietf.org/doc/html/draft-ietf-lsr-isis-srv6-extensions-19>.
[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-09, , <https://datatracker.ietf.org/doc/html/draft-ietf-lsr-ospfv3-srv6-extensions-09>.
[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-03, , <https://datatracker.ietf.org/doc/html/draft-ietf-spring-srv6-srh-compression-03>.
[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/insa-unyte/vpp>.
[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>.
[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>.
[RFC9252]
Dawra, G., Ed., Talaulikar, K., Ed., Raszuk, R., Decraene, B., Zhuang, S., and J. Rabadan, "BGP Overlay Services Based on Segment Routing over IPv6 (SRv6)", RFC 9252, DOI 10.17487/RFC9252, , <https://www.rfc-editor.org/info/rfc9252>.
[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>.

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 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 (see https://www.rfc-editor.org/rfc/rfc7011.html#section-7).

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 (see https://www.rfc-editor.org/rfc/rfc7011.html#section-7).

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