Dial-Up and Leased Lines

When connecting to a public network, for example one administered by a phone company, you must choose between using dial-up access and leased lines.

A leased line is a line allocated to you by the network's administration. You pay for exclusive use of this line and for it to be configured to your specification. You can only change the characteristics of this line in consultation with your network provider. For leased lines, the service provider typically provides a suitable modem for connecting your DTE to the network.

Dial-up access means that there is no particular line allocated for your use. When a DTE needs to access the public network, it uses a modem to place a call to the network. This means that there are no rental or set-up charges as there are with a leased line; charging is done on a per-call basis. Most dial-up services use the X.32 protocols to provide a degree of authentication, so the network knows the call is coming from an approved user.