Understanding Remote Access Service

Microsoft's Remote Access Service (RAS) provides TCP/IP over phone lines by treating your modem as a network adapter. TCP/IP applications that run over a network can run over a serial connection. iFIX can use the TCP/IP interface provided by RAS to communicate with other iFIX nodes over asynchronous lines.

RAS client and server software are standard with Windows. In general, a RAS client node dials into a RAS server node. A RAS client can dial in and access resources on a Windows RAS server's network. The Windows software allows multiple RAS clients to be connected simultaneously.

Although RAS allows up to 256 clients to dial into a server simultaneously, the practical limit when RAS is used with the iFIX is significantly less. This is due to the additional resources that iFIX requires to communicate. Each simultaneous connection requires a separate modem on the server. Before you incorporate RAS into your production environment, it is strongly recommended that you test the configuration using multiple connections.

Using iFIX in conjunction with a RAS server provides the following capabilities:

  • Alarm Summary objects are available.
  • Data and alarms are available with one pair of modems.
  • Access to the Alarm Startup Queue is available.
  • File transfer using Microsoft networking over RAS is available.
  • Multiple remote nodes can dial into a server simultaneously.

Use the following guidelines when incorporating RAS into your iFIX network:

  • Only use modems with a minimum speed of 9600 baud. Verify that when the RAS connection is made that the modems are connected at a high speed. The faster the baud rate, the better performance you can expect.
  • Use the Port Status on both the RAS client and server to troubleshoot connection problems and monitor ongoing communication. Refer to the RAS documentation for more information on using Port Status to troubleshoot communication.
  • When browsing on the RAS client to access a remote SCADA server, you can improve performance by copying the file, nodename.TAG, from the SCADA server's PDB path to the View client's PDB path.


See Also

Important Notice

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