Implementation

NetBIOS is often described as a "Session Layer" protocol and a variety of transport systems have been used in different implementations. Some of these implementations are described in the chapter called Encapsulation in various protocols and encapsulating . The protocols used to encapsulate NetBIOS are generally well understood and well documented; what is often not well understood are implementations of NetBIOS "on the wire" in a "raw" un-encapsulated form.

Two implementations of NetBIOS "on the wire" are considered here: The original NetBIOS in IBM PC Networks (See the section called Comparison of NetBIOS protocols in IBM PC Network in the appendix called NetBIOS protocols in IBM PC Network ) and NetBIOS Frames Protocol on 802.2 networks. Although the IBM PC Network version was developed first, the current NetBIOS Frames Protocol on 802.2 networks is emphasized in this document as being the more relevant.

It should be noted that the frames in NetBIOS in IBM PC Networks are more complex and seem less consistent than frames in the NetBIOS Frames Protocol on 802.2 networks. The IBM PC Networks implementation separates in to the protocols mentioned above, where as all the frames in NetBIOS Frames Protocol on 802.2 networks are more consistent in their format.