IsisLinkStatePDUID
The 8-byte Link State PDU (LSP) ID, consisting of the 6-byte SystemID of the originating IS; a one-byte PseudoNode ID, which is 0 unless the LSP represents the topology of a LAN; and a one-byte LSP fragment number that is issued in sequence, starting with 0. Non-zero PseudoNode IDs need to be unique to the IS but need not match the IfIndex.