vendor proprietary Network Layer Message if network_layer_message_type in the range X'80' - X'FF'

[duffy-ocraven]

Vendor Proprietary Network Layer Message is specified if Bit 7 of the control octet is 1 and the network_layer_message_type octet contains a value in the range X'80' - X'FF'. For vendor proprietary Network Layer Messages, it is mandated that a Vendor_ID field appears after the network_layer_message_type as a two octet value, high octet first. The remaining UDP/BLVC/NPDU content that follows, if any, is vendor defined.

[duffy-ocraven]

If a 1-octet Vendor_ID field is observed, then end-of-packet, that is malformed, because a 2-octet Vendor_ID field is required.