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Generic Alerts for X.25 Link Access Protocol Balanced And X.25 Physical Level Errors

IP.com Disclosure Number: IPCOM000099798D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 108K

Publishing Venue

IBM

Related People

Geise, D: AUTHOR [+3]

Abstract

As follows: 1) The X.25 subsystem detected a modem failure. The data carrier detect and/or data set ready signals are not operating correctly. 2) The X.25 subsystem detected a modem failure. The local auto call unit is not responding. 3) The X.21 connection to the PDSN could not be established. The X.25 subsystem has detected either a fault condition or that the DCE (Data Circuit-Terminating Equipment) is not ready. Fig. 1: X.25 Physical Layer Generic Alerts Defined by the Communications Manager The OS/2 Extended Edition Version 1.2 Communication Manager (CM) provides an X.25 subsystem that allows users to write non-SNA X.25 applications that communicate through a packet-switched data network (PSDN). Additionally, all of the CM's SNA applications (e.g.

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Generic Alerts for X.25 Link Access Protocol Balanced And X.25 Physical Level Errors

       As follows:
1)   The X.25 subsystem detected a modem failure. The data carrier
detect and/or data set ready signals are not operating correctly.
2)   The X.25 subsystem detected a modem failure. The local auto call
unit is not responding.
3)   The X.21 connection to the PDSN could not be established. The
X.25 subsystem has detected either a fault condition or that the DCE
(Data Circuit-Terminating Equipment) is not ready. Fig. 1:   X.25
Physical Layer Generic Alerts Defined by the Communications Manager
The OS/2 Extended Edition Version 1.2 Communication Manager (CM)
provides an X.25 subsystem that allows users to write non-SNA X.25
applications that communicate through a packet-switched data network
(PSDN). Additionally, all of the CM's SNA applications (e.g., 3270
Emulation, 5250 Work Station Feature, file transfer) and APIs (e.g.,
APPC, EHLLAPI, SRPI, LU A) may be configured to communicate through
an X.25 PSDN using the Qualified Logical Link Control (QLLC) protocol
and the X.25 subsystem.

      The CCITT X.25 Recommendation defines three communication
layers:  the physical layer, link layer and the packet layer.

      The physical layer defines the electrical and mechanical
interfaces used to connect to a network. The CM supports the
following physical interfaces:
         . X.21 bis/V.24
         . X.21 bis/V.35
         . X.21

      The link layer protocol defined for use by X.25 is HDLC/LAPB
(Link Access Protocol Balanced). This protocol allows data to be
reliably exchanged between the network and Data Terminal Equipment
(DTE).

      The packet layer makes a single real data link appear to be
several logical links called virtual circuits. A virtual circuit is a
logical connection from end to end through the network. The CM allows
a single X.25 link to have up to 128 virtual circuits.
1)   The Communications Manager received a frame with an Information
field (I-field) which was too long and sent a frame reject.
2)   The Communications Manager received a frame with an invalid N(R)
value (the remote DTE uses the number N(R) to acknowledge that its
received one or more information frames) and sent a frame reject.
3)   The Communications Manager has retried a command the maximum
number of times without receiving an appropriate response.
4)   The Communications Manager received an unexpected DISC
(disconnect) command during information transfer.
5)   The Communications Manager sent a SABM (set asynchronous
balanced mode) command to initialize the link and received a DM
(disconnected mode) res...