1.8 Vendor-Extensible Fields
It is important to understand that the choice of name used by a higher-layer protocol or application is up to that protocol or application and not NetBIOS over TCP/IP (NBT). As such, this section provides a convention for use by higher-layer protocols and applications, but the extensions in this document do not enforce the use of this convention.
The recommended convention is for higher-layer protocols and applications to use the first 15 bytes of the Internet host name of the machine (padded with spaces if shorter than 15 bytes) followed by a 1-byte NetBIOS suffix chosen by the higher-layer protocol or application.<1><2>
The recommended convention allows for 256 NetBIOS suffix values and vendors can define a new value. However, there is no mechanism to acquire a unique value and hence collisions are possible if multiple vendors define the same NetBIOS suffix values. It is up to each higher-layer protocol or application to specify what NetBIOS suffix it uses, or how the NetBIOS name is constructed if it does not use this recommended convention.