Browse Prior Art Database

Dynamic ISDN Data Link Control/Synchronous Data Link Control Protocol Protocol Recognition and Initialization for the ISDN B-CHL

IP.com Disclosure Number: IPCOM000111157D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 144K

Publishing Venue

IBM

Related People

Fisher, ME: AUTHOR [+3]

Abstract

A method is disclosed for dynamically recognizing the Synchronous Data Link Control (SDLC) or the ISDN Data Link Control (IDLC) protocol on an ISDN B-channel. The method further describes how one side of the B-channel protocol can begin communicating with the recognized protocol.

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

Dynamic ISDN Data Link Control/Synchronous Data Link Control Protocol
Protocol Recognition and Initialization for the ISDN B-CHL

      A method is disclosed for dynamically recognizing the
Synchronous Data Link Control (SDLC) or the ISDN Data Link Control
(IDLC) protocol on an ISDN B-channel.  The method further describes
how one side of the B-channel protocol can begin communicating with
the recognized protocol.

      The problem this invention attempts to solve is how to add
support for SDLC or IDLC to a device that currently supports only one
of these protocols, but with minimal changes to the upper layers of
software and minimal or no customer configuration.

      The solution is to create a software layer under, or inside of,
the existing IDLC or SDLC layer that will do the following:

1.  Dynamically recognize whether the protocol is primary SDLC,
    negotiable SDLC, secondary SDLC or IDLC.

2.  If the recognized protocol is not directly supported, provide
    appropriate conversions.  For example:

          If the protocol is SDLC, but software supports only IDLC,
    then automatically convert received SDLC frames to IDLC
    primitives before sending the data to the higher layer software;
    automatically send SDLC frames when given IDLC primitives.  (The
    details of this step are not addressed here.)

      The protocol recognition procedure will now be described in
detail, using the example of a device with software that supports
only IDLC:

      Note: To distinguish a new IDLC entity that has implemented the
protocol recognition algorithm described here, the term IDLC is
introduced.

      For an IDLC' entity to recognize the protocol to which it is
attached, it must do the following:

I -- Recognize if the Remote is an IDLC' Entity

o   The local IDLC' entity must first send a frame that can only be
    recognized by another IDLC' entity.  This frame will be called
    the IDLC' recognition frame and the local IDLC' entity should
    start the IDLC response timer after it sends the frame.  The
    frame may be a two-byte "SDLC" frame with an address of zero,
    X'00', (the "no stations" SDLC address) and a second byte that
    will arbitrarily be defined as an IDLC Unnumbered Information
    (UI) command control byte, X'13', (an invalid SDLC control byte).

o   If the remote protocol is SDLC, it should discard the frame
    because '00'X is the "no stations" address.

o   If the remote protocol is IDLC, the frame will be too short and
    will also be discarded.

o   Only if the remote protocol is IDLC', will it recognize the
    frame.  If the remote protocol is IDLC', it will also have sent
    an IDLC' recognition frame.  The receipt of an IDLC' recognition
    frame immediately before or after having sent an IDLC'
    recognition frame may be interpreted as the the correct IDLC'
    response.  Recognition is now c...