CLNP (`clnp`)

Layer: L3 (network)
Header: variable length
Notes: CLNP / ES-IS (P2), IS-IS (P2), OSI encapsulation (P2)

Reached from

Lower layer	Selector	Value
`llc`	First 8 bits of the payload when `dsap` = 254 (0xfe)	129 (0x81)
`ppp`	First 8 bits of the payload when `protocol` = 35 (0x0023)	129 (0x81)

Fields

Field	Type	Default	Auto	Description
`nlpid`	`enum(8)`	`129` (clnp)		Network layer protocol identifier (0x81 = CLNP).
`length_indicator`	`uint(8)`		Length of the header in octets	Header length in octets, up to the end of the options (Auto).
`version`	`uint(8)`	`1`		Version / protocol ID extension (1).
`lifetime`	`uint(8)`	`32`		Remaining lifetime in units of 500 ms.
`sp`	`uint(1)`		Number of items of `segmentation`	SP: segmentation permitted; the segmentation part is present (Auto from the segmentation part).
`ms`	`uint(1)`	`0`		MS: more segments follow.
`er`	`uint(1)`	`1`		E/R: send an error report if the PDU is discarded.
`pdu_type`	`enum(5)`	`28` (dt)		PDU type: 0x1c DT (data), 0x1d MD (multicast data), 0x01 ER (error report), 0x1e ERQ / 0x1f ERP (echo request / reply).
`segment_length`	`uint(16)`		Length of the header and payload in octets	Length of the whole PDU, header and data (Auto).
`checksum`	`uint(16)`		Fletcher checksum over the header	ISO 8473 Fletcher checksum of the header (Auto). 0 = checksum not used.
`destination`	`nsap`	`49.0001.0000.0000.0002.00`		Destination NSAP address.
`source`	`nsap`	`49.0001.0000.0000.0001.00`		Source NSAP address.
`segmentation`	`list<struct>` — `sp` items	`[]`		Segmentation part (data unit identifier, segment offset, total length), present when SP is set. The total length is not computed.
`options`	`tlv` — up to offset `length_indicator` of the group	`[]`		Options (8-bit code / 8-bit length) up to the length indicator: security, QoS maintenance, priority, source routing, recording of route, padding, reason for discard.

`nlpid`

Value	Name
129 (0x81)	`clnp`

`pdu_type`

Value	Name
1	`er`
28	`dt`
29	`md`
30	`erq`
31	`erp`

`segmentation`

Each item is a group of the fields below.

Field	Type	Default	Auto	Description
`data_unit_identifier`	`uint(16)`
`segment_offset`	`uint(16)`
`total_length`	`uint(16)`

`options`

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

Type	Name	Value fields
197 (0xc5)	`security`	`value`
195 (0xc3)	`qos_maintenance`	`value`
205 (0xcd)	`priority`	`value`
200 (0xc8)	`source_routing`	`route_type`, `next_address`, `addresses`
203 (0xcb)	`recording_of_route`	`route_type`, `next_address`, `addresses`
204 (0xcc)	`padding`	`data`
193 (0xc1)	`reason_for_discard`	`reason`, `pointer`

`options` › `security`

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

`options` › `qos_maintenance`

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

`options` › `priority`

Field	Type	Default	Auto	Description
`value`	`uint(8)`

`options` › `source_routing`

Field	Type	Default	Auto	Description
`route_type`	`enum(8)`
`next_address`	`uint(8)`
`addresses`	`list<struct>` — rest of the PDU

`options` › `source_routing` › `route_type`

Value	Name
0 (0x00)	`partial`
255 (0xff)	`complete`

`options` › `source_routing` › `addresses`

Each item is a group of the fields below.

Field	Type	Default	Auto	Description
`address`	`nsap`

`options` › `recording_of_route`

Field	Type	Default	Auto	Description
`route_type`	`enum(8)`
`next_address`	`uint(8)`
`addresses`	`list<struct>` — rest of the PDU

`options` › `recording_of_route` › `route_type`

Value	Name
0 (0x00)	`partial`
255 (0xff)	`complete`

`options` › `recording_of_route` › `addresses`

Each item is a group of the fields below.

Field	Type	Default	Auto	Description
`address`	`nsap`

`options` › `padding`

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

`options` › `reason_for_discard`

Field	Type	Default	Auto	Description
`reason`	`enum(8)`
`pointer`	`uint(8)`

`options` › `reason_for_discard` › `reason`

Value	Name
0 (0x00)	`general`
1 (0x01)	`checksum`
2 (0x02)	`congestion`
3 (0x03)	`header_syntax`
4 (0x04)	`segmentation_needed`
5 (0x05)	`incomplete_pdu`
6 (0x06)	`duplicate_option`
128 (0x80)	`destination_unreachable`
129 (0x81)	`destination_unknown`
144 (0x90)	`source_routing_unspecified`
145 (0x91)	`source_routing_syntax`
146 (0x92)	`source_routing_unknown_address`
147 (0x93)	`source_routing_path_not_acceptable`
160 (0xa0)	`lifetime_expired_in_transit`
161 (0xa1)	`lifetime_expired_reassembly`
176 (0xb0)	`unsupported_option`
177 (0xb1)	`unsupported_version`
178 (0xb2)	`unsupported_security`
179 (0xb3)	`unsupported_source_routing`
180 (0xb4)	`unsupported_recording_of_route`
192 (0xc0)	`reassembly_interference`

Sample templates

clnp-dt — templates/protocols/l3/clnp-dt.wpg.yaml
clnp-er — templates/protocols/l3/clnp-er.wpg.yaml
clnp-erq — templates/protocols/l3/clnp-erq.wpg.yaml

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