Losing Connections with HP JetDirect Printers

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1

SYMPTOMS

Windows NT version 3.1 may lose connections with Hewlett-Packard (HP) JetDirect printers. This can result in a continuous Online or Status Unknown for the printer in Print Manager. The print queue then stops responding (hangs) and does not restart until the server is restarted.

RESOLUTION

To correct this problem, do the following:

• Make sure the latest version of HPMON.DLL is loaded. Run Print Manager. Select any print queue using an HP JetDirect. From the Printer menu, choose Properties, and then choose Settings. Choose the About button to display the version information. It should be version A.00.14.

  NOTE: This is the version shipping with Windows NT version 3.5 and is available for Windows NT version 3.1 in Service Pack 3 or the HPMON.DLL provided in the HPMON.EXE Application Note, which is located in Microsoft Download Library (MSDL) and the Internet on FTP.MICROSOFT.COM.

• Increase the DLC Timers settings located in Print Manager to be similar to the version information above. To adjust the DLC Timers, select a printer using a JetDirect, and then choose Properties from the Printer menu. Choose the Settings button, and then choose Options (do this from the server because HPMON.DLL cannot run remotely). The range for each of the three settings of the DLC Timers is 1 to 10. Try doubling each setting first, and then adjust them more if you need to. This affects HPMON as a whole for the server, so you only need to make this adjustment on one printer. Note: the new settings will not take affect until you restart the server.
• HPMON by default uses windowing to communicate with the JetDirect card. This means HPMON will send say five packets to the JetDirect and only expect one acknowledgment for all five. Sometimes if the printer is slow to accept incoming data, the buffers on the JetDirect will become full and the JetDirect cannot accept all of the packets at once. The JetDirect will not send the acknowledgment and HPMON must attempt to synchronize between the two. Under stress, this causes problems because traffic increases between HPMON and the JetDirect with retransmissions. The connection may fail during this time. In cases like this, it is best to turn the windowing off. By doing so, HPMON will send one packet and wait for an acknowledgment before sending the second packet. This provides for much better error handling. While this change does affect the network speed to the printer, the speed is only moderately affected and is still much faster than printers can render the print. The above cases of flow control can actually be faster then with the retransmissions of failed windows of data.

  To disable windowing, you may modify the Registry. However, if you extract the new HPMON available on MSDL and the Internet with the "-D" (without the quotation marks) parameter, and then run the automated Install program for HPMON, you do not have to modify the Registry.

  WARNING: Using Registry Editor incorrectly can cause serious, system-

        wide problems that may require you to reinstall Windows NT to correct
        them. Microsoft cannot guarantee that any problems resulting from the
        use of Registry Editor can be solved. Use this tool at your own risk.
  

  1. Start REGEDT32.EXE and locate the following Registry subkey:

        HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control
           \Print\Monitors\Hewlett-Packard Network Port\Options
  
     2. From the Edit menu, choose Add Value. Enter "MaximumXmitsWindow"
        (without the quotation marks) in the Value Name field. Select
        REG_DWORD for the Data Type. Enter 1 in the Data field and choose OK.
  
     3. Exit REGEDT32.