How RAS Supports X.25 Networks (131968)

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How RAS Supports X.25 Networks

RAS does not know what medium it is running over. It does not know about the X.25 protocol, just as it does not know about how phone lines and modem equipment work. The RAS server uses the Eicon Technology WAN Services Eicon drivers and an internal Eicon X.25 adapter to convert the X.25 protocol to the serial (RS232) protocol signals (and vice versa), or it can send and receive serial signals to and from an external X.25 PAD (packet assembler/disassembler), in which case, no Eicon software and hardware is necessary because the X.25 PAD does the protocol conversion.

Some RAS client versions can also be configured with the Eicon driver and adapter or the external PAD, but usually the clients use a modem to call the X.25 network provider's dial-up PAD, which is also a modem. After the RAS client's modem and the X.25 provider's dial-up PAD connect, the X.25 provider usually requires callers to identify themselves for billing purposes. To support caller identification, most RAS clients can run a customized command script, and some can also go into an interactive post- connect Terminal mode, to allow the client to send the user name and password.

NOTE: The external PAD configuration mentioned above is not supported in Windows for Workgroups 3.11 and Windows NT Workstation and Server versions 3.1, 3.5, and 3.51. However, there are no known reasons why it should not work.

Overview of X.25 Networks

An X.25 network transmits data with a packet-switching protocol. This protocol relies on an elaborate worldwide network of packet-forwarding nodes (DCEs) that can deliver an X.25 packet to its designated address. X.25 also requires additional hardware such as an X.25 Smart card or a PAD.

For additional information, see the Windows NT 3.5 Server "Remote Access Service" manual, chapter 6.

Reasons to Use an X.25 network for RAS

In addition to transmitting data more reliably than regular phone lines, X.25 connections supply bandwidths of up to 56 kilobytes (K) (64K in Europe).

However, in areas where ISDN is available, Microsoft recommends using ISDN rather than X.25, because ISDN is much faster without compromising reliability.

For additional information on ISDN and RAS, see the Windows NT 3.5 Server "Remote Access Service" manual, page 8, or the Windows NT 3.5 RAS online Help.