WinNT 3.5 RAS Compression Lost If Linked to Older RAS Version

• Microsoft Windows NT Workstation version 3.5
• Microsoft Windows NT Server version 3.5

SYMPTOMS

While you have a Remote Access Service (RAS) link established, you notice two symptoms:

• In the Port Status dialog boxes of the RAS server and client, the Incoming and Outgoing Compression fields indicate loss of software compression, because they display 0 percent instead of a number greater than zero.
• The effective throughput is much less than usual (presumably because of zero software compression).

NOTE: These symptoms do not occur if the RAS client and server are both running Windows NT 3.5.

CAUSE

The software compression method used in Windows NT version 3.1 RAS and Windows for Workgroups version 3.11 RAS is not compatible with the software compression used in Windows NT version 3.5.

RESOLUTION

• To work around the throughput problem, use modem hardware compression.

  This, however, cannot give you as much throughput as RAS software compression. Modem hardware compression is not monitored by RAS; therefore, the Incoming and Outgoing Compression fields always display zero.

• To resolve the display and throughput problems, upgrade Windows NT 3.5 to version 3.51.

  NOTE: Service Pack 2 for Windows NT 3.5 also fixes the throughput problem, but not the display problem.

For best performance, Microsoft suggests you configure the RAS client software on Windows for Workgroups 3.11, Windows NT 3.1, and Windows NT 3.51 (or Windows NT 3.5 with Service Pack 2 installed) as follows:

1. In Remote Access, make sure the Disable Software Compression option in the Options menu is not checked.

2. Choose the Edit button, then choose the Modem button, and select the following:

       - Enable Hardware Flow Control
       - Enable Modem Error Control
   

   Clear the Enable Modem Compression check box so software compression and modem compression are not used at the same time (as this reduces throughput).

MORE INFORMATION

If you still don't get compression after installing Windows NT 3.51, verify that your downlevel RAS software has the drivers for software compression installed.

Software

Compression in Windows for Workgroups 3.11 and Windows NT 3.1 RAS Clients

Software compression is available by default in these RAS clients unless you set the Disable Software Compression option from the Options menu or you purchased your copy of Windows for Workgroups 3.11 or Windows NT 3.1 after February 1994. You can tell whether or not you have RAS software compression by using the following information:

Windows for Workgroups 3.11:

   Filename     Bytes   Compression
   --------------------------------
   RASMAC.386   49209   YES
   RASMAC.386   27193   NO

   Filename       Bytes    Compression
   -----------------------------------
   ASYNCMAC.SYS   53188    YES
   ASYNCMAC.SYS   53716    YES
   ASYNCMAC.SYS   33732    NO