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The NetBIOS User Datagram Protocol (UDP) provides packet transmission from source to destination. UDP is an unreliable datagram delivery protocol.
NetBIOS User Datagram Protocol is comparable with the Datagram Delivery Protocol (DDP) in AppleTalk, or IP in the TCP/IP suite of protocols, or IPX in Novell's IPX/SPX protocol suite. It is important to note that the NetBIOS User Datagram Protocol differs from datagram protocols in other protocol suites; the NetBIOS User Datagram Protocol is designed specifically to provide a datagram delivery service and not necessarily to provide a foundation for higher level protocols. Where as in other protocol suites the datagram protocol supports transport and session layer protocols running over the datagram protocol, here there is a separate Session Management Protocol which does not make use of the NetBIOS User Datagram Protocol. The relationship is illustrated in the the appendix called Open Systems Interconnection (OSI) Reference Model .
UDP packets are sent between Named systems (see the section called Addressing - NetBIOS names above) or are broadcast from one Named system to all Names on the network.
The original User Datagram Protocol is described in the appendix called NetBIOS protocols in IBM PC Network in the section the section called Datagram Packet in IBM PC Network in the appendix called NetBIOS protocols in IBM PC Network .
The "DATAGRAM" frame (0x08) is used to send a datagram to a name.
The frame begins with a two byte length field with a value of 0x002C followed by the two byte frame deliminator field 0xEFFF; these fields are transmitted byte reversed. These fields are followed by the one octet command frame which has a value of 0x08 identifying it as an "DATAGRAM" frame.
Seven reserved octets are followed by sixteen octets used to identify the destination name of the datagram. The following sixteen octets identify the source name sending the datagram. A variable number of octets contain the data or payload of the datagram.
The "DATAGRAM BROADCAST" frame (0x09) is used to broadcast a datagram to all names on the network.
The frame begins with a two byte length field with a value of 0x002C followed by the two byte frame deliminator field 0xEFFF; these fields are transmitted byte reversed. These fields are followed by the one octet command frame which has a value of 0x09 identifying it as an "DATAGRAM" frame.
Seven reserved octets are followed by a further sixteen octets which are also reserved rather than identifying the destination name as in the case of "DATAGRAM" frames. The following sixteen octets identify the source name sending the datagram. A variable number of octets contain the data or payload of the datagram.
Table 5. Datagram frames (Octets in order transmitted.)
| Data frame | Data frame | ||
|---|---|---|---|
| Field Name | Length | DATAGRAM | DATAGRAM BROADCAST |
| Length | 2 | 0x2C | 0x2C |
| 0x00 | 0x00 | ||
| Deliminator | 2 | 0xFF | 0xFF |
| 0xEF | 0xEF | ||
| Command | 1 | 0x08 | 0x09 |
| Data 1 | 1 | Reserved | Reserved |
| Data 2 | 2 | Reserved | Reserved |
| Reserved | Reserved | ||
| XMIT Cor | 2 | Reserved | Reserved |
| Reserved | Reserved | ||
| RSP Cor | 2 | Reserved | Reserved |
| Reserved | Reserved | ||
| Destination Name | 16 | Name of receiver | Reserved |
| Source Name | 16 | Name of sender | Name of sender |
| Optional | Datagram | Datagram |
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