Packet (N_PDU)

In ISO Standards, the name Network Protocol Data Unit (N_PDU in short) is used. For various reasons we decided to use Packet name instead.

The packets are created during segmentation of a diagnostic message. Each diagnostic message consists of at least one Packet (N_PDU).

Packet contains following information:

Network Address Information (N_AI) - packet addressing

Network Data Field (N_Data) - packet data

Network Protocol Control Information (N_PCI) - packet type

Network Address Information

Network Address Information (N_AI) field carries all addressing related information.

It identifies:

the sender
recipient(s) of the packet
addressing type (Physical Addressing or Functional Addressing) used

Network Data Field

Network Data Field (N_Data) carries diagnostic message data. It might be an entire diagnostic message data (if a diagnostic message fits into one packet) or just a part of it (if segmentation had to be used to divide a diagnostic message into smaller parts).

For some communication buses, some packets might not carry any data (e.g. CAN Flow Control) as they are used to manage the packets flow.

Network Protocol Control Information

Network Protocol Control Information (N_PCI) identifies the type of Packet (N_PDU). N_PCI values and their interpretation are bus specific.