ES-IS ESH (`esis_esh`)

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)
`esis`	`pdu_type`	2 (re-decodes this layer)

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.
`number_of_source_addresses`	`uint(8)`		Number of items of `source_addresses`	Number of source addresses (Auto).
`source_addresses`	`list<struct>` — `number_of_source_addresses` items	1 items		NSAP addresses served by the end system.
`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, address mask, SNPA mask, suggested ES configuration timer.

`nlpid`

Value	Name
130 (0x82)	`esis`

`pdu_type`

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

`source_addresses`

Each item is a group of the fields below.

Field	Type	Default	Auto	Description
`address`	`nsap`

`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	Description
197 (0xc5)	`security`	`value`
195 (0xc3)	`qos_maintenance`	`value`
205 (0xcd)	`priority`	`value`
225 (0xe1)	`address_mask`	`mask`
226 (0xe2)	`snpa_mask`	`mask`
198 (0xc6)	`es_configuration_timer`	`seconds`

`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` › `address_mask`

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

`options` › `snpa_mask`

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

`options` › `es_configuration_timer`

Field	Type	Default	Auto	Description
`seconds`	`uint(16)`

Sample templates

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