Maximizing Routing Performance with Netflex-3 Network Adapter

This article discusses how to maximize the throughput of a Windows NT server that is running the Routing and Remote Access Service.

Windows NT 4.0 Service Pack 3 includes an updated driver for the Compaq Netflex-3 Ethernet network card. Using a combination of this updated driver and some new registry entries that are supported by this driver, you can increase the performance of your Routing and Remote Access Service server.

The updated driver is Netflex3.sys and must be manually installed. To install this driver, perform the following steps:

1. Click the Start button, point to Settings, and then click Control Panel.
2. Double-click the Network icon.
3. Click the Adapters tab, click Add, and then click Have Disk.
4. The updated Netflex-3 driver is located in the following folder:
   

      D:\drvlib\netcard\x86\netflex3
   						

   
   where D: is the letter of your CD-ROM drive.
5. Select the appropriate adapter, and then click OK.
6. Click Close, and then restart the computer when prompted.

The following registry settings only apply to the Compaq Netflex-3 card. Other network adapter cards may have similar settings but the value names will vary. Please consult with your network adapter manufacturer for more information.

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 Registry Editor (Regedt32.exe) and locate the following subkey:
   

      HKEY_Local_Machine\System\CurrentControlSet\Services\ 
         Netflex3X\Parameters
   						

   
   where X is each instance of the network adapter.
2. With Parameters selected, click Edit, click Add Value, and then type the following information:
   

      Value Name:  MaxReceives
      Value Type:  REG_DWORD
      Data:        500 (decimal)
   						

3. With Parameters selected, click Edit, click Add Value, and then type the following information:
   

      Value Name:  FixedIntMod
      Value Type:  REG_DWORD
      Data:        5000 (decimal)
   						

4. Quit Registry Editor and restart the Routing and Remote Access Service server.

MaxReceives increases the size of non-paged pool memory used to buffer packets.

FixedIntMod (fixed interrupt moderation) sets the amount of interrupts per second to a fixed number. By default, Windows NT uses dynamic interrupt moderation that may interrupt the CPU for every packet received. Choosing the best number of interrupts per second for fixed interrupt moderation will depend on your router load. The number you choose may queue interrupts (more efficient) for servicing or service interrupts too often (less efficient). Testing should be done when using these registry settings to ensure that performance is improved in your environment.