CFM LTR (`cfm_ltr`)

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

Reached from

Lower layer	Selector	Value
`ethernet2`	`ethertype`	35074 (0x8902)
`dot1q`	`ethertype`	35074 (0x8902)
`dot1ad`	`ethertype`	35074 (0x8902)
`cfm`	`opcode`	4 (0x04) (re-decodes this layer)

Fields

Field	Type	Default	Description
`md_level`	`uint(3)`	`0`	Maintenance domain / MEG level (0-7).
`version`	`uint(5)`	`0`	CFM version (0; 1 for R-APS of G.8032v2).
`opcode`	`enum(8)`	`4` (ltr)	OpCode: 1 CCM, 2 LBR, 3 LBM, 4 LTR, 5 LTM, 33 AIS, 35 LCK, 37 TST, 39 Linear APS, 40 R-APS, 41 MCC, 42 LMR, 43 LMM, 45 1DM, 46 DMR, 47 DMM, 52 CSF, 53 1SL, 54 SLR, 55 SLM …
`use_fdb_only`	`uint(1)`	`1`	UseFDBonly: the forwarding database alone decides the egress port.
`fwd_yes`	`uint(1)`	`0`	FwdYes: the LTM was relayed.
`terminal_mep`	`uint(1)`	`1`	TerminalMEP: the reply comes from the target MEP.
`flags_reserved`	`uint(5)`	`0`
`first_tlv_offset`	`uint(8)`	`6`	Offset of the first TLV from the end of this field (constant for each OpCode).
`transaction_id`	`uint(32)`	`1`	Loopback / linktrace transaction identifier.
`reply_ttl`	`uint(8)`	`63`	Linktrace TTL.
`relay_action`	`enum(8)`	`1` (rly_hit)	Relay action: 1 RlyHit, 2 RlyFDB, 3 RlyMPDB.
`tlvs`	`tlv` — up to and including the first item of type 0, or the end of the PDU	3 items	TLVs (8-bit type, 16-bit length of the value, Auto): Sender ID, Port Status, Data, Interface Status, Reply Ingress / Egress, LTM / LTR Egress Identifier, Organization-Specific, Test, closed by the End TLV (type 0).

`opcode`

Value	Name
1 (0x01)	`ccm`
2 (0x02)	`lbr`
3 (0x03)	`lbm`
4 (0x04)	`ltr`
5 (0x05)	`ltm`
33 (0x21)	`ais`
35 (0x23)	`lck`
37 (0x25)	`tst`
39 (0x27)	`linear_aps`
40 (0x28)	`ring_aps`
41 (0x29)	`mcc`
42 (0x2a)	`lmr`
43 (0x2b)	`lmm`
45 (0x2d)	`one_dm`
46 (0x2e)	`dmr`
47 (0x2f)	`dmm`
48 (0x30)	`exr`
49 (0x31)	`exm`
50 (0x32)	`vsr`
51 (0x33)	`vsm`
52 (0x34)	`csf`
53 (0x35)	`one_sl`
54 (0x36)	`slr`
55 (0x37)	`slm`

`relay_action`

Value	Name
1 (0x01)	`rly_hit`
2 (0x02)	`rly_fdb`
3 (0x03)	`rly_mpdb`

`tlvs`

Type 8 bits, length 16 bits.
The length counts the value only.
Unknown types are kept as raw value octets.

Type	Name	Value fields
0 (0x00)	`end`	(type only, no length or value)
1 (0x01)	`sender_id`	`chassis_id_length`, `chassis_id_subtype`, `chassis_id`, `management_address`
2 (0x02)	`port_status`	`port_status`
3 (0x03)	`data_tlv`	`value`
4 (0x04)	`interface_status`	`interface_status`
5 (0x05)	`reply_ingress`	`ingress_action`, `ingress_mac`, `ingress_port_id`
6 (0x06)	`reply_egress`	`egress_action`, `egress_mac`, `egress_port_id`
7 (0x07)	`ltm_egress_identifier`	`egress_identifier`
8 (0x08)	`ltr_egress_identifier`	`last_egress_identifier`, `next_egress_identifier`
31 (0x1f)	`organization_specific`	`oui`, `subtype`, `value`
32 (0x20)	`test`	`pattern_type`, `test_pattern`

`tlvs` › `sender_id`

Field	Type	Default	Auto
`chassis_id_length`	`uint(8)`		Size of `chassis_id` in octets
`chassis_id_subtype`	`enum(8)`	`4` (mac_address)
`chassis_id`	`bytes` — `chassis_id_length` octets	`02 00 00 00 00 01`
`management_address`	`bytes` — rest of the PDU

`tlvs` › `sender_id` › `chassis_id_subtype`

Value	Name
1 (0x01)	`chassis_component`
2 (0x02)	`interface_alias`
3 (0x03)	`port_component`
4 (0x04)	`mac_address`
5 (0x05)	`network_address`
6 (0x06)	`interface_name`
7 (0x07)	`local`

`tlvs` › `port_status`

Field	Type	Default	Auto	Description
`port_status`	`enum(8)`	`2` (up)

`tlvs` › `port_status` › `port_status`

Value	Name
1 (0x01)	`blocked`
2 (0x02)	`up`

`tlvs` › `data_tlv`

Field	Type	Default	Auto	Description
`value`	`bytes` — rest of the PDU

`tlvs` › `interface_status`

Field	Type	Default	Auto	Description
`interface_status`	`enum(8)`	`1` (up)

`tlvs` › `interface_status` › `interface_status`

Value	Name
1 (0x01)	`up`
2 (0x02)	`down`
3 (0x03)	`testing`
4 (0x04)	`unknown`
5 (0x05)	`dormant`
6 (0x06)	`not_present`
7 (0x07)	`lower_layer_down`

`tlvs` › `reply_ingress`

Field	Type	Default
`ingress_action`	`enum(8)`	`1` (ok)
`ingress_mac`	`mac`	`02:00:00:00:00:02`
`ingress_port_id`	`bytes` — rest of the PDU

`tlvs` › `reply_ingress` › `ingress_action`

Value	Name
1 (0x01)	`ok`
2 (0x02)	`down`
3 (0x03)	`blocked`
4 (0x04)	`vid`

`tlvs` › `reply_egress`

Field	Type	Default
`egress_action`	`enum(8)`	`1` (ok)
`egress_mac`	`mac`	`02:00:00:00:00:02`
`egress_port_id`	`bytes` — rest of the PDU

`tlvs` › `reply_egress` › `egress_action`

Value	Name
1 (0x01)	`ok`
2 (0x02)	`down`
3 (0x03)	`blocked`
4 (0x04)	`vid`

`tlvs` › `ltm_egress_identifier`

Field	Type	Default	Auto	Description
`egress_identifier`	`uint(64)`	`2199023255553`

`tlvs` › `ltr_egress_identifier`

Field	Type	Default	Auto	Description
`last_egress_identifier`	`uint(64)`	`2199023255553`
`next_egress_identifier`	`uint(64)`	`2199023255554`

`tlvs` › `organization_specific`

Field	Type	Default	Auto	Description
`oui`	`uint(24)`
`subtype`	`uint(8)`
`value`	`bytes` — rest of the PDU

`tlvs` › `test`

Field	Type	Default	Auto	Description
`pattern_type`	`enum(8)`
`test_pattern`	`bytes` — rest of the PDU

`tlvs` › `test` › `pattern_type`

Value	Name
0 (0x00)	`null_without_crc`
1 (0x01)	`null_with_crc`
2 (0x02)	`prbs_without_crc`
3 (0x03)	`prbs_with_crc`

Constraints

Level	Rule
warning	`first_tlv_offset` = 6

Sample templates

cfm-ltr — templates/protocols/oam/cfm-ltr.wpg.yaml

Keyboard shortcuts

wpg Documentation