Browse Prior Art Database

Technique for Establishing Switched Connections through Various Devices

IP.com Disclosure Number: IPCOM000106393D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 4 page(s) / 147K

Publishing Venue

IBM

Related People

Fussell, DK: AUTHOR [+3]

Abstract

Disclosed is a technique for establishing connections over switched lines using a state machine driven by external files that describe the actions of the state machine. The external file contains all the commands to be issued to establish the connection, all possible responses to these commands, and the actions to be taken when each particular response occurs. The program that implements the state machine does not have to be customized to a particular communications device.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 40% of the total text.

Technique for Establishing Switched Connections through Various Devices

      Disclosed is a technique for establishing connections over
switched lines using a state machine driven by external files that
describe the actions of the state machine.  The external file
contains all the commands to be issued to establish the connection,
all possible responses to these commands, and the actions to be taken
when each particular response occurs.  The program that implements
the state machine does not have to be customized to a particular
communications device.

      Currently available modems and switched line connection
equipment all have very sophisticated capabilities, many of which are
quite similar.

      Most modems have abundant commands for allowing a user or
application to control these capabilities.  These commands are much
alike for many different modems, but the sequence of instructions
given to one modem for accomplishing a given task will not get the
same result when issued to another modem.  Also, modems have
different command sets from CBXs and other connection equipment.

      All of this equipment is designed for essentially the same
purpose, namely, to establish and maintain a communication link
between two computers.  It is possible to build common software that
will handle communication links successfully, independent of the
connection equipment being used.

      The problem that arises when writing communications software is
how to allow for the differences in equipment (modems and CBXs) but
still use their similarity.  When establishing a connection over a
switched line, a dialog between the modem and/or CBX must must occur.
The modem and/or CBX must be initialized, dial, possibly issue
commands to the remote machine, answer, hang-up, etc.  A common piece
of software can handle this for almost any modem or CBX.  But it is
ineffective to imbed the exact modem commands into this software,
since the software then becomes specific to that modem or device.

      Most solutions to this problem involve the use of script or
command files, which run at the very top layer of an application and
simulate a user entering the modem commands manually through a
keyboard.  The Dialog Descriptor File, described here, was created as
a means to record modem specific information and modem specific
dialogues in a way that allows low-level access to the commands
necessary to operate a given modem or CBX.  This file is associated
with the given piece of communication equipment, contains all the
instructions needed to direct that modem or CBX, and is provided as
input directly to the low-level software that obtains and terminates
communications links.  The application or user does not have to pay
attention on these areas, and in fact, the same Dialog Descriptor
File may be used by many applications.

      A Dialog Descriptor File consists of one or more dialogues,
which have one or more actions and response...