NetBIOS is often described as a "Session Layer" protocol and a variety of transport systems have been used in different implementations. Particularly because NetBIOS is a non-routable protocol, it has often been implemented using other routable protocols to provide the transport. It has traditionally been the NetBIOS API that has been the "standard". In most implementations (certainly NetBIOS over TCP/IP and NetBIOS over IPX), encapsulation has been implemented to ensure that higher level protocols (such as SMB) can run over the encapsulated protocol in the same way as they would run over NetBIOS Frames Protocol, NBF (otherwise known as NetBEUI or NetBIOS). Thus it is important to understand the NetBIOS Frames Protocol, NBF in order to understand the various encapsulation implementations.

IPX/SPX are the protocols native to Novell NetWare. Details of these protocols can be found in: Novell's Guide to NetWare LAN Analysis, see Novell introduced an implementation of NetBIOS over IPX in 1986. The implementation uses IPX datagrams to carry the NetBIOS Frames protocol described above. The IPX addressing scheme is compared with the native NetBIOS and other schemes in above. In IPX/SPX networks, a 48 bit address (usually a MAC address) identifies a node on a network and a 32 bit address identifies each network. Thus IPX is a routable protocol requiring relatively little administration, which makes it a useful means of implementing NetBIOS. IPX packets are broadly analogous to IP packets in the TCP/IP suite of protocols; IPX packets provide an unreliable datagram delivery service. The structure of the IPX Header is given below for reference: The IPX Header Checksum (2 bytes) Length (2 bytes) Transport Control (1 byte) Packet Type (1 byte) 0 or 4 for IPX, 5 for SPX, 17 (0x11) for NCP, 20 (0x14) WAN broadcast Destination Node Address (6 bytes) Destination Network Address (4 bytes) Destination Socket (2 bytes) Source Node Address (6 bytes) Source Network Address (4 bytes) source Socket ( 2 bytes) The Destination Socket indicates the service being carried over IPX, some examples and the identifier for NetBIOS are given below: 0x451 NetWare Core Protocol (NCP) 0x452 Service Advertising Protocol packet (SAP) 0x453 Routing Information Protocol packet (RIP) 0x455 NetBIOS packet 0x456 Diagnostic packet 0x457 Serialization packet 0x4000 to 0x8000 Dynamically assigned for use with file servers etc.

Microsoft have implemented NetBIOS over the NWLink IPX/SPX compatible transport. (NWLink is a clone of Novell's IPX/SPX). The Microsoft implementation is compatible with Novell's NetBIOS over IPX. Microsoft sometimes refers to NetBIOS over IPX as NBIPX. Length IPX Field NBIPX 2 Checksum   2 Length 1 Transport Control 1 Packet Type 0 or 4 for IPX, 20 (0x14) WAN broadcast 6 Destination Node Address 4 Destination Network Address 2 Destination Socket 6 Source Node Address 4 Source Network Address 2 source Socket n Data NBIXP packet Length Field 1 NBIPX Connection Control flag 1 Data Stream type 2 Source connection id 2 Destination connection id 2 Send Sequence number 2 Total data length 2 Offset 2 Data length 2 Receive Sequence number 2 Bytes received n Data

The MAP/TOP Users Group Technical Report Specification of NetBIOS Interface and Name Service Support by Lower Layer OSI Protocols, Version 1.0, September 27, 1989, is reproduced as an appendix in The Open Group CAE Specification "Protocols for X/Open PC Interworking: SMB, Version 2."

Communications Machinery Corporation has implemented a NetBIOS interface for ISO protocols. "Netbios for ISO Networks", see

NetBIOS can be carried over PPP (Point-to-Point Protocol). The relevant RFCs are: RFC 2097 The PPP NetBIOS Frames Control Protocol (NBFCP) PROPOSED STANDARD RFC1661 STD0051 The Point-to-Point Protocol (PPP)STANDARD RFC 2153 PPP Vendor Extensions INFORMATIONAL

NetBIOS can be used to encapsulate other protocols by providing a virtual circuit over which other protocols can be transmitted. This is the opposite situation to those described above where other protocols provide the transport for NetBIOS.

A standard method of encapsulating the Internet Protocol (IP) datagrams on NetBIOS networks is described in: RFC 1088 A Standard for the Transmission of IP Datagrams over NetBIOS Networks