ESMC (`esmc`)

Layer: L2 (data link)
Header: variable length
Notes: PTP / ESMC / CFM / R-APS / 802.3ah OAM (P2)

Reached from

Lower layer	Selector	Value
`ethernet2`	First 8 bits of the payload when `ethertype` = 34825 (0x8809)	10 (0x0a)

Fields

Field	Type	Default	Auto	Description
`subtype`	`uint(8)`	`10`		Slow Protocols subtype (0x0a = organization specific).
`itu_oui`	`uint(24)`	`6567`		ITU-T OUI (00-19-a7).
`itu_subtype`	`uint(16)`	`1`		ITU-T subtype (1 = ESMC).
`version`	`uint(4)`	`1`		ESMC version (1).
`event_flag`	`uint(1)`	`0`		Event flag: 1 for an event PDU sent at once after a QL change, 0 for the once-a-second information PDU.
`reserved`	`uint(3)`	`0`
`reserved2`	`uint(24)`	`0`
`tlvs`	`tlv` — rest of the PDU	2 items		TLVs (8-bit type, 16-bit length including the 3-octet header, Auto): QL TLV with the SSM code, Extended QL TLV with the enhanced SSM code, SyncE clock identity and cascaded clock counts. Octets after them (padding) are kept as one raw item.

`tlvs`

Type 8 bits, length 16 bits.
The length counts the type and length fields too.
An unknown type ends the typed decoding (the rest becomes one raw item).

Type	Name	Value fields	Description
1 (0x01)	`ql`	`unused`, `ssm_code`
2 (0x02)	`extended_ql`	`enhanced_ssm_code`, `synce_clock_identity`, `flags`, `cascaded_eeecs`, `cascaded_eecs`, `reserved`

`tlvs` › `ql`

Field	Type	Default	Auto	Description
`unused`	`uint(4)`	`0`
`ssm_code`	`enum(4)`	`2` (prc)

`tlvs` › `ql` › `ssm_code`

Value	Name
0	`stu`
1	`prs`
2	`prc`
4	`ssu_a`
7	`st2`
8	`ssu_b`
10	`st3`
11	`sec`
12	`smc`
13	`st3e`
14	`prov`
15	`dnu`

`tlvs` › `extended_ql`

Field	Type	Default	Auto	Description
`enhanced_ssm_code`	`enum(8)`	`255` (none)
`synce_clock_identity`	`uint(64)`	`144116287553929217`
`flags`	`flags(8)`	`0x0`
`cascaded_eeecs`	`uint(8)`	`1`
`cascaded_eecs`	`uint(8)`	`0`
`reserved`	`bytes(5)`	`00 00 00 00 00`

`tlvs` › `extended_ql` › `enhanced_ssm_code`

Value	Name
32 (0x20)	`eprtc`
33 (0x21)	`prtc`
34 (0x22)	`eeec`
35 (0x23)	`eprc`
255 (0xff)	`none`

`tlvs` › `extended_ql` › `flags`

Bit	Mask	Name
0	1 (0x01)	`mixed_eec_eeec`
1	2 (0x02)	`partial_chain`

Constraints

Level	Rule
warning	`subtype` = 10
warning	`itu_oui` = 6567
warning	`version` = 1

Sample templates

esmc-event-dnu — templates/protocols/timing/esmc-event-dnu.wpg.yaml
esmc-ql-prc — templates/protocols/timing/esmc-ql-prc.wpg.yaml