Protocol: ISO 10589 / IS-IS
PDU Part: Common Part
Field: type
Length: 5 bits
Contents: type of PDU.
The type value identifies one of the following PDU types:
> Point-to-point IS-IS hello
> Level-1 LAN IS-IS hello
> Level-2 LAN IS-IS hello> Level-1 link state
> Level-2 link state
> Level-1 complete sequence numbers
> Level-2 complete sequence numbers
> Level-1 partial sequence numbers
> Level-2 partial sequence numbers
All PDU types use the same 'common part' and different protocol fields afterwards.