Ref: 07000004
Title: NETBIOS General Information (part 1)
Date: 07/13/88

Copyright 3Com Corporation, 1991.  All rights reserved.

by Derek R. Flickinger
From the December 1987 issue of LAN Magazine:

BIOS stands for Basic Input/Output System.  ROMBIOS is a generic way
for the disk Operating System and application program software to
access and manage hardware in a personal computer.  It is a
standardized set of function calls that allow programmers to handle
things like disk I/O's, printer requests, screen output and keyboard
input.  These calls will accept the same parameters and return the same
status codes, independent of the hardware or processor type within a
personal computer.

Although there are different ROMBIOS implementations to handle 8088-;
80286- and 80386-based machines, the calls to access the hardware work
the same on any machine.  Different manufacturers write their own BIOS
code, but the interface from a programmer's view is still the same.  A
programmer can write directly to the hardware for whatever reason, but
the code will not be generic for any machine and may not work with
every vendor.

NetBIOS is very similar to ROMBIOS.  NetBIOS is the interface for
communicating with devices connected in a local area network
environment.  NetBIOS is the Input/Output System for talking across a
network.  It consists of a standardized set of software interrupts for
function calls for establishing and using network Sessions, sending
Datagrams, and setting up NetBIOS Names for the devices attached to
the network.

In the NetBIOS world...a...form of communications is referred to as
DATAGRAMS.  These are general "Public Broadcasts" across the network.
The information is meant for one person, even though anyone listening
can hear it.  These broadcasts are sent out with no immediate
confirmation that the intended recipient has heard it.  Chances are
pretty good that if one is listening, one will hear.

The other method of communicating...would be referred to as a NetBIOS
SESSION.  A named device listens for a call; someone calls; they
exchange data or a remote transaction is performed; and then they hang
up.  This link implies that there is error checking and assumes that
both named devices understand each other.

Once a NetBIOS Communications Session is established, the protocol that
is usually "spoken" at the application level is termed a SERVER MESSAGE
BLOCK or SMB.  It defines what language the devices will use when
talking to each other.

What the SMBs are saying is really independent of NetBIOS and its
calls.  Microsoft developed SMBs to be used for the communications
standard within their generic MS-Net LAN with its redirector and Remote
File Access capabilities.  Essentially, SMBs are a way to organize
requests or transactions once a NetBIOS Session is established.  They
are used at the Application and Presentation levels of the seven-layer
OSI model and it is through the SMB transactions that files,
directories, or printers on a different machine may be accessed, open,
closed and manipulated.  Although they are not considered to be part of
NetBIOS, SMBs are the protocols that communicate over NetBIOS Sessions.
When IBM licensed MS-Net for their original PC Network it made NetBIOS
and SMB's the de-facto standard for Local Area Network peer-to-peer
communications.

(continued in NETBIOS part 2)
