Swisscom

Binzring 17 Zurich 8045 Switzerland thomas.graf@swisscom.com

Huawei

benoit.claise@huawei.com

This document introduces new IP Flow Information Export (IPFIX) information elements to identify the SRv6 Segment Routing Header dimensions and SRv6 Control Plane Protocol that traffic is being forwarded with.

A new type of Routing Extension Header called Segment Routing Header (SRH) is defined by which is used for applying Segment Routing (SR) on the IPv6 data plane. Three routing protocol extensions, OSPFv3 Extensions, IS-IS Extensions, BGP Prefix Segment Identifiers (Prefix-SIDs) and one Path Computation Element Communication Protocol (PCEP) Extension have been defined to propagate Segment Identifiers (SIDs) for the IPv6 data plane. This document defines eight new IPFIX Information Elements (IEs) and two new subregistries within the "IPFIX Information Elements" registry , respectively for the new SRH dimensions and routing protocol and PCEP extensions.

This section defines and describes the new IPFIX IEs. 8-bit flags defined in the SRH. 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. 128-bit IPv6 address that represents an SRv6 segment. Ordered basicList of zero or more 128-bit IPv6 addresses in the SRH that represents the SRv6 segment list. The Segment List is encoded starting from the active segment of the SR Policy. Exposes the SRH Segment List as defined in section 2 of as series of n octets. 8-bit unsigned integer defining the number of route segments remaining to reach the end of the segment list. Exposes the SRH and its TLV's as defined in section 2 of as series of n octets. Name of the routing protocol or PCEP extension from where the active SRv6 segment has been learned from.

By using ipv6SRHSegmentBasicList(TBD4), ipv6SRHSegmentsLeft (TBD6), ipv6SRHSegmentType(TBD8) and forwardingStatus(89) it is possible to identify how many packets are forwarded or dropped if dropped, for which reasons, identify the control plane protocol which defined the active segment, the SRv6 segment list and how many SRv6 segments are left.

This document requests IANA to create new IEs (see table1) and two new subregistries called "IPFIX IPv6 SRH Flags" (table 2) and "IPFIX IPv6 SRH Segment type" (table 3) under the "IPFIX Information Elements" registry available at and assign the following code initial points.

Note to the RFC-Editor: Please replace TBD1 - TBD12 with the values allocated by IANA Please replace the [RFC-to-be] with the RFC number assigned to this document

Name: ipv6SRHFlags ElementID: TBD1 Description: This Information Element identifies the 8-bit flags defined in the SRH. Values for this Information Element are listed in the "IPFIX IPv6 SRH Flags" registry, see [IANA-IPFIX]. 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 . Experts need to check definitions of new values for completeness, accuracy, and redundancy.

Abstract Data Type: unsigned8 Data Type Semantics: flags Reference: [RFC-to-be], RFC8754

Name: ipv6SRHTag ElementID: TBD2 Description: This Information Element identifies 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 Reference: [RFC-to-be], RFC8754

Name: ipv6SRHSegment ElementID: TBD3 Description: This Information Element identifies the 128-bit IPv6 address that represents an SRv6 segment. Abstract Data Type: ipv6address Data Type Semantics: default Reference: [RFC-to-be], RFC8754

Name: ipv6SRHSegmentBasicList ElementID: TBD4 Description: This Information Element identifies the Ordered basicList [RFC6313] of zero or more 128-bit IPv6 addresses in the SRH that represents the SRv6 segment list. The Segment List is encoded starting from the active segment of the SR Policy. Abstract Data Type: basicList Data Type Semantics: list Reference: [RFC-to-be], RFC8754

Name: ipv6SRHSegmentListSection ElementID: TBD5 Description: Exposes the SRH Segment List as defined in section 2 of as series of n octets. Abstract Data Type: octetArray Data Type Semantics: default Reference: [RFC-to-be], RFC8754

Name: ipv6SRHSegmentsLeft ElementID: TBD6 Description: This Information Element identifies the 8-bit unsigned integer defining the number of route segments remaining to reach the end of the segment list. Abstract Data Type: unsigned8 Data Type Semantics: quantity Reference: [RFC-to-be], RFC8754

Name: ipv6SRHSection ElementID: TBD7 Description: This Information Element exposes the SRH and its TLV's as defined in s ection 2 of as series of n octets. Abstract Data Type: octetArray Data Type Semantics: default Reference: [RFC-to-be], RFC8754

Name: ipv6SRHSegmentType ElementID: TBD8 Description: This Information Element identifies 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" registry, see [IANA-IPFIX]. 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 . Experts need to check definitions of new values for completeness, accuracy, and redundancy.

Abstract Data Type: unsigned8 Data Type Semantics: identifier Reference: [RFC-to-be]

The zero or more 128-bit IPv6 addresses in the SRH [RFC8754] can be exported in two different ways, with two different IPFIX IEs: ipv6SRHSegmentBasicList ipv6SRHSegmentListSection The ipv6SRHSegmentBasicList encodes the SID list of IPv6 addresses with a basicList, specified in the IPFIX Structured Data . 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 ipv6SRHSegmentListSection, 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. It is not expected that an exporter would support both ipv6SRHSegmentBasicList and ipv6SRHSegmentListSection at the same time.

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

I would like to thank Pierre Francois, Yao Liu and Paolo Lucente for their review and valuable comments.

In this section an example is provided to show the encoding format for the newly introduced IEs.

In this example, the Template ID is 256, which will be used in the Data Record. The field length for ipv6SRHSegmentBasicList 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 .

The data set is represented as follows: