ES-IS (`esis`)

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

Reached from

Lower layer	Selector	Value
`llc`	First 8 bits of the payload when `dsap` = 254 (0xfe)	130 (0x82)
`ppp`	First 8 bits of the payload when `protocol` = 35 (0x0023)	130 (0x82)

Fields

Field	Type	Default	Auto	Description
`nlpid`	`enum(8)`	`130` (esis)		Network layer protocol identifier (0x82 = ES-IS).
`length_indicator`	`uint(8)`		Length of the header in octets	Length of the PDU in octets (Auto).
`version`	`uint(8)`	`1`		Version / protocol ID extension (1).
`reserved`	`uint(8)`	`0`
`reserved_type`	`uint(3)`	`0`
`pdu_type`	`enum(5)`	`2` (esh)		PDU type: 2 ESH (end system hello), 4 ISH (intermediate system hello), 6 RD (redirect).
`holding_time`	`uint(16)`	`30`		Holding time in seconds.
`checksum`	`uint(16)`		Fletcher checksum over the header	ISO 8473 Fletcher checksum of the PDU (Auto). 0 = checksum not used.
`data`	`bytes` — rest of the PDU	`""`		Rest of the PDU after the fixed part (opaque octets).

`nlpid`

Value	Name
130 (0x82)	`esis`

`pdu_type`

Value	Name
2	`esh`
4	`ish`
6	`rd`

Next layer

The next layer is selected by pdu_type; when the field is Auto the builder writes the value of the protocol stacked above.

Value	Protocol	Note
2	`esis_esh`	re-decodes this layer
4	`esis_ish`	re-decodes this layer
6	`esis_rd`	re-decodes this layer

Sample templates

esis-generic — templates/protocols/routing/esis-generic.wpg.yaml