Initially ISDN was designed with one or two twisted pair cables. The maximum data rate provided here is too low for many business applications. Broadband ISDN requires fiber optic cable. It can support data rates of greater than 600 Mbps. ISDN is a connection-oriented network and so is different from a packet switched network.
All data is packaged in fixed size cells.
Since ATM is for reliable fiber optic cable, it provides a minimum of support for error control and flow control. Therefore it cannot be used effectively with less reliable subnetworks. Many applications such as GUI applications and WWW applications such as a web browser will not work with character based interfaces that are traditionally supported by modems over telephone lines. These applications require graphical interfaces. It has more standardized features than SLIP but SLIP is more widely supported.