Connections to a Network from Outside
Three options for connecting over a telephone service:
- Dial-up connections.
- Integrated Services Digital Network(ISDN) - A method of sending voice and data information on a digital phone line. Two 64Kbps B-channels with one 16Kbps D channel is provided with basic ISDN service. The D-channel is used tor call control and setup. Basic ISDN can provide 128Kbps speed capability. 23 B-channels and one D channel is provided with Primary ISDN.
- Leased Lines - This involves the leasing of a permanent telephone line between two locations.
Remote Communication Protocols
- Serial Line Internet Protocol (SLIP) - Allows computers to connect to the internet with a modem. No error checking or data compression. Only supports TCP/IP.
- Point to Point Protocol (PPP) - Provides error checking and data compression. Also supports multiple network protocols such IPX/SPX and NetBEUI in addition to TCP/IP. Supports dynamic allocation of IP addresses.
Remote Access Service
Remote Access Service (RAS) with Windows NT allows users connecting to the network using a modem to use network resources. The NT RAS server can handle 256 connections. Windows NT RAS servers provide the following security features:
- User account security
- Encryption between the DUN (dial up networking) client and the server
- Callback capability
The client software is called Dial up networking (DUN) in windows NT4 and Windows95. For NT 3.51 and Windows 3.1 it is called a RAS client. These clients may be used to connect to the internet through an internet service provider (ISP).