EtherType Protocol Identification of In-situ OAM Data

In-situ Operations, Administration, and Maintenance (IOAM) records operational and telemetry information in the packet while the packet traverses a particular network domain. The term "in-situ" refers to the fact that the IOAM data fields are added to the data packets rather than being sent within packets specifically dedicated to OAM. This document proposes a new Ethertype for IOAM and defines how IOAM data fields are carried as part of encapsulations where the IOAM data fields follows an encapsulation header that uses an EtherType to denote the type of protocol data unit. Examples of these protocols are GRE and Geneve ). This document outlines how IOAM data fields are encoded in these encapsultion headers.

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 when, and only when, they appear in all capitals, as shown here.

Abbreviations used in this document: Edge-to-Edge Generic Network Virtualization Encapsulation Generic Routing Encapsulation In-situ Operations, Administration, and Maintenance Operations, Administration, and Maintenance Proof of Transit

When the IOAM data fields are included within an encapsulation that identifies the next protocol using an EtherType (e.g., GRE or Geneve) the presence of IOAM data fields are identified with TBD_IOAM. When this EtherType is used, an additional IOAM header is also included. This header indicates the type of IOAM data fields that follows, and the next protocol that follows the IOAM data fields.

The IOAM encapsulation is defined as follows. 8-bit field defining the IOAM Option type, as defined in Section 5.1 of . 8 bit Length field contains the length of the IOAM header in 4-octet units. 16 bits Next Protocol Type field contains the protocol type of the protocol data unit following IOAM protocol header. Protocol Type is defined to be an EtherType value from . An implementation receiving a packet containing a Protocol Type which is not listed in one of those registries SHOULD discard the packet. IOAM option header and data is present as specified by the IOAM-Option-Type field, and is defined in Section 5 of . Multiple IOAM options MAY be included within the encapsulation header. For example, if a GRE encapsulation contains two IOAM options before the data payload, the Next Protocol field of the first IOAM option will contain the value of TBD_IOAM, while the Next Protocol field of the second IOAM option will contain the EtherType indicating the type of the data payload.

The IOAM EtherType can be used with any encapsulation that uses EtherType to denote the type of the protocol data unit. The following sections show how it can be used when GRE and Geneve are used as the encapsulation header.

When IOAM data fields are carried in GRE, the IOAM encapsulation defined above follows the GRE header, as shown in .

| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Checksum (optional) | Reserved1 (Optional) | G +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ R | Key (optional) | E +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Sequence Number (Optional) | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+ | IOAM-Type | IOAM HDR len| Next Protocol | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I ! | O ! | A ~ IOAM Option and Data Space ~ M | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+ | | | Payload + Padding (L2/L3/ESP/...) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]> The GRE header and fields are defined in . The GRE Protocol Type value is set to TBD_IOAM. shows two example protocol header stacks that use GRE along with IOAM. IOAM Option-Types (the below diagram uses "IOAM" as shorthand for IOAM Option-Types) are sequenced in behind the GRE header that follows the "outer" header of the next protocol unit.

When IOAM data fields are carried in Geneve, the IOAM encapsulation defined above follows the Geneve header, as shown in .

| |G +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |E | Virtual Network Identifier (VNI) | Reserved | |N +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |E | Variable Length Options | |V +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+E | IOAM-Type | IOAM HDR len| Next Protocol | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I ! | O ! | A ~ IOAM Option and Data Space ~ M | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+ | | | Inner header + Payload + Padding (L2/L3/ESP/...) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]> The Geneve header and fields are defined in . The Geneve Protocol Type value is TBD_IOAM.

This document describes the encapsulation of IOAM data fields in the encapsulation header such as GRE and Geneve that uses EtherType to denote the protocol data unit. Security considerations of the specific IOAM data fields for each case (i.e., Trace, Proof of Transit, and E2E) are described in . As this document describes new protocol fields within the existing encapsulation, any security considerations of the respective encapsulation header is applicable. When the encapsulation is GRE, the security considerations of is applicable. When the encapsulation is Geneve, the security considerations of is applicable. IOAM data fields SHOULD be integrity protected (e.g., with ) to detect changes made by a device between the IOAM encapsulating node and the IOAM decapsulating node.

A new EtherType value is requested to be added to the IANA registry by IEEE Registration Authority. The description should be "In-situ OAM (IOAM)".

We would like to thank Nagendra Kumar Nainar for the contribution.