Windows NT Uses DLC for IBM Connectivity and Network Printing

 Last reviewed: May 8, 1997
Article ID: Q102450

The information in this article applies to:
  • Microsoft Windows NT operating system, version 3.1
  • Microsoft Windows NT Advanced Server, version 3.1

SUMMARY

Data link control (DLC) is a transport protocol defined by IBM. It is mainly used to communicate with IBM mainframes and minicomputers, typically model 3270 or AS/400 machines. In addition, Windows NT also uses DLC to communicate with network printers such as the Hewlett- Packard (HP) LaserJet 4 Si.

MORE INFORMATION

DLC works with Token Ring (802.5) or Ethernet (802.3) NDIS MAC drivers.

DLC is available to 32-bit Windows NT-based applications and 16-bit MS-DOS-based and Windows-based applications. Since there are few 32-bit 3270 emulators available, DLC is typically by 16-bit 3270 and 5250 (AS/400) emulators. These are character-mode or graphics-mode MS-DOS-based programs or Windows-based programs that communicate with an IBM mainframe using 3270 terminal emulation.

The following 16-bit 3270 and 5250 emulation programs should work normally with Windows NT:

For IBM 3270: 

   AttachMate Extra! for Windows v 3.3, 3.4 and 3.5
   AttachMate Extra! for MS-DOS  v 2.23
   IBM PC/3270 v 2.0 for Windows
   IBM PC/3270 v 2.0 for MS-DOS
   IBM PC/3270 v 3.0 for Windows
   IBM PC/3270 v 3.0 for MS-DOS
   Eicon Access for Windows v 3.11, 3.14
   Dynacomm Elite/3270
For IBM 5250: 

   IBM PCS v 2.0
   NSA Elite/400
Windows NT also uses DLC to communicate with network printers, such as the HP LaserJet 4 Si. Such printers have a network interface card (NIC) that contains a MAC and a DLC protocol stack. Print jobs are sent to these printers as DLC-level frames over the network, instead of over the parallel port. The advantages of such printer setups are increased print job download speed and the ability to have the printer physically distant from its server. Note that even though the printer has the ability to receive print jobs over the network, with Windows NT, it is usually controlled by a print server that has sole control of the network connection to the printer (meaning that other computers cannot connect to the printer, even if they know the network address of the printer). This is because DLC uses service access points (SAPs) and only one is available for connections. Once a remote computer has connected to the SAP, subsequent connect requests are denied at the printer.

Additional query words: adapter prodnt PROT005
Keywords : kbnetwork ntprotocol NTSrvWkst
Version : 3.1
Platform : WINDOWS

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Last reviewed: May 8, 1997
© 1998 Microsoft Corporation. All rights reserved. Terms of Use.