RAS allows remote clients to connect through a telephone line or other wide area network (WAN) link to the RAS server; from there RAS allows those clients to access resources on the network. Remote users can access network resources as though they were logged on to a machine directly connected to the network. To allow a user to connect remotely to the RAS server, use the administrative tool User Manager for Domains and grant the user dialin permission. You can set three forms of dialin permission:
- No call back:
Gives the user permission to dial in to the network using the RAS server.
- Set by caller:
Terminates the connection after the user dials in to the RAS server. The RAS server dials the user back at the phone number the user specifies. This function is called callback.
- Preset to:
Also uses callback, but the server always calls the user back using a phone number preset on the server.
RAS on Windows NT provides both dial-in and dial-out capability, supporting up to 256 simultaneous inbound connections on Windows NT Server but only one inbound connection on Windows NT Workstation. Clients that want to connect to a RAS server must have dial-up networking or a similar application installed. RAS is fully integrated into the Windows NT security model and supports encrypted authentication, auditing, callback, and intermediary hardware security hosts. Users can be restricted to access to the RAS server only, or to access through the RAS server to all resources on the network.
Windows NT RAS supports clients connecting over the following media:
- The Public Switched Telephone Network (PSTN) using modems
- Dedicated Integrated Services Digital Network (ISDN) lines
- X.25 packet-switching networks
- A null modem cable
You can establish RAS connections with Windows NT by using any common local area network (LAN) transport protocol and the following WAN protocols:
- Point-to-Point Protocol (server-side or client-side), including Point-to-Point Tunneling Protocol (PPTP) for establishing virtual private network (VPN) connections
- Serial Line Internet Protocol (client-side only)
An optionally available Windows NT 4 component called Routing and Remote Access Service (RRAS) replaces the existing RAS on Windows NT and provides additional Internet Protocol (IP) routing functionality.