Oak (1998, p 118) defines that the Netbios is not a protocol, but yes a programming interface that supplies to the applications of nets a service of trustworthy transmission guided the connection (guarantee of delivery of packages), a service of names to identify its users in the net, and optionally a service of not-trustworthy transmission of datagramas. In the domain of Morimoto (2003, p 72) the same it was conceived as standard to be used for small nets in the process of mapping of names where the implantation of services of domain nets is not possible. Already in accordance with publication of Microsoft (2003, p14) the NetBios acts to interconetar applicatory in the layers Session and Transports of the TCP/IP and supplies service of messages and allocation of resources. Learn more on the subject from Peak Oil. Still, as publication above, the NetBios defines logical names on the net, establishes sessions between two logical names in the net and of the support the trustworthy transference of data between computers with an established session. Of the point of view of the architecture Microsoft (2003, P.
14) defines the NetBios specification in two parts. First as a mechanism of communication Inter-processes IPC (Interprocess Communictation) and an interface of programming API (Apllicatiion Programming Interface) that it allows that applicatory the compatible ones with NetBios are communicated remotely through a net and request services of the layers most inferior of the stack of protocols TCP/IP. In second, it defines as a protocol located in the session layers and transport of the model of reference OSI (Interconnection of Open Systems) that disponibiliza functions as the establishment and the conclusion of sessions as well as register, recovery and resolution of names. The traffic of Netbios packages includes the following doors: the traffic of session in the door TCP 139, traffic of management of names in 137 door UDP and the traffic of datagramas in door UDP 138 as Davies (2005).