ISDN Support for Windows for Workgroups RAS

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The ISDN configuration offers a much faster communication speed than standard telephone lines because it replaces the analog telephone system with a digital system. For example, a standard telephone line can typically transfer data with a modem at a speed of 9600 bits per second (bps); ISDN communicates without a modem at speeds of 64 or 128 kilobits per second. As with a local area network, you can connect to an ISDN system from a remote location using RAS, provided that the proper ISDN lines, service, and adapters are in place.

Below are the steps required to configure ISDN parameters in Windows for Workgroups 3.11 RAS:

1. Choose the Remote Access Services icon and choose Add from the Phone Book toolbar.
2. In the Phone Book Entry dialog box, choose Advanced and then select the Any ISDN Port option as the PORT setting.
3. Choose the ISDN icon to configure ISDN settings.
4. Select an appropriate Line Type setting for the ISDN connection. The Line Type options are 64K Digital (highest quality), 56K Digital, and 56K Voice (lowest quality). Contact the ISDN provider for details on the Line Type selection.
5. Both the Negotiate Line Type and Enable Hardware Compression options are selected by default.
   
   Negotiate Line Type allows RAS to communicate at the selected line type but negotiates to a lower quality line type if necessary. This negotiation depends on the condition of the ISDN line (for example, noise on the line affects negotiation).
   
   Below are examples of when Negotiate Line Type option may be disabled:
   
   
   • The ISDN tariff rates and the capability of the ISDN line have been previously set up to support a specific line type.
   • The ISDN system supports only Voice grade lines in the area. Choose the 56K Voice option as the line type.
   • Negotiate line type is unnecessary if 64K Digital connection is supported in the your area and is selected as the line type in RAS.
   NOTES:
   
   
   • Do not disable Negotiate Line Type if channel negotiation is needed. Channel negotiation is automatically enabled when the Negotiate Line Type option is selected. If you disable the Negotiate Line Type option, RAS cannot operate when channel negotiation is needed.
     
     You must use channel negotiation if you connect to an ISDN system that has two or more ISDN lines and has been set up to use channel negotiation. If you enable the RAS software portion of channel negotiation and do not have the ISDN card in the hardware-selected channel negotiation mode, your system may stop responding (hang), or you may be unable to communicate with RAS on the ISDN lines. (RAS will not know how to format the data for transmission and will also have problems communicating with the hardware.) Contact your ISDN provider to find out if your card supports channel negotiation.
   • The Enable Hardware Compression option uses the ISDN card's built-in compression techniques to compress data before transmitting it. To use the card's hardware compression, RAS software compression must first be turned off. To turn off RAS software compression, choose Options from the Phone Book toolbar and select Disable Software Compression.
6. The Channels To Use setting is set to 1 by default. The number of channels set should not be changed unless the ISDN card supports the use of more than one ISDN channel.
   
   
   • If your ISDN card supports the use of more than one ISDN channel (known as channel aggregation) and the card is set up accordingly, you can increase the number of channels in use to improve throughput. If more than one channel is selected, you must enter each telephone number for the number of channels selected (separated by colons, not spaces). For example, if three channels are selected, the Phone Number entry might read as follows:

     555-5555:444-4444:333-3333

   • Not all ISDN drivers let you restrict channel aggregation. If your computer is configured to receive calls and you have a non- restricting driver, ensure that remote clients specify only one or two channels. This prevents one user with several ISDN cards from monopolizing all the channels on the server.

The online help file available in Remote Access Services is a valuable resource for configuring RAS with an ISDN configuration. Online help provides information on how to set up RAS with ISDN and details many of the supported configurations for an ISDN system.