3 - ES-IS CLNS - End System to Intermediate System / ISO 9542
CLNS ES-IS (Fixed Part) PCI
Network-Layer Protocol ID (1 byte)
Length Indicator (1 byte) (ISO 9542)
Version / PID Extension (1 byte)
Type (5 bits)
Holding Time (2 bytes)
Checksum (2 bytes)
Address Part (n bytes)
Options (n bytes)