|NetBIOS, NetBEUI, NBF, NBT, NBIPX, SMB, CIFS Networking: NetBIOS to CIFS|
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Token Ring is becoming less popular with many organizations moving to Ethernet. Token Ring is discussed here because of it's importance in the history of NetBIOS and understanding of NetBIOS.
When IBM introduced Token-Ring, an emulator for NetBIOS was produced. The NetBIOS Extended User Interface (NetBEUI) was introduced in 1985. NetBIOS was no longer implemented only on a set of propriety protocols, but also on 802.2 frames. The implementation on Token-Ring was the first implementation over 802.2 and provides a reference model. Detailed information can be found in the IBM manual: IBM LAN Technical Reference, see Bibliography IBM LAN Technical Reference IEEE 802.2 and NetBIOS Application Program Interfaces.
A full description of Token Ring is beyond the scope of this document; some basic information on Token Ring and its use with NetBIOS is given below.
There are two kinds of Token Ring frames: Media Access Control (MAC) frames and Non-MAC frames. MAC frames carry Token Ring management information between nodes, Non-MAC frames carry user data. The non-MAC frames contain IEEE 802.2 Logical Link Control frames which in turn can contain NetBIOS frames.
Table 1. Non-MAC Token Ring Frame Structure
|Token Ring frame||802.2 Frame detail||NBF frame|
|Start Delimiter (SDEL) 1 octet|
|Access Control (AC) 1 octet|
|Frame Control (FC) 1 octet|
|Destination Address 6 octets|
|Source Address 6 octets|
|IEEE 802.2 Logical Link Control||DSAP 2 octets|
|SSAP 2 octets|
|Control 1 or 2 octets|
|Data 46-1500 octets||NetBIOS header|
|Frame Check sequence (FCS) 4 octets|
|End Delimiter (EDEL) 1 octet|
|Frame Status (FS) Check sequence 1 octet|