ATM: ATM stands for Asynchronous Transfer Mode. ATM is widespread application its use as part of broadband. ATM does not provide error control and flow control mechanisms. ATM is the data transfer interface for B-ISDN. ATM is not based on HDLC,but it is based on completely new frame format known as cell, that provides minimum processing overhead. The cell has a fixed length of 53 octets or 424 bits.
Frame Relay: Frame Relay is a data link control facility designed to provide a capability for use over high-speed packet-switched networks. Frame relay provides a more efficient packet switching than X.25 and widespread use, not only in ISDN but in other networking context. A critical component of Frame relay is congestion control.
ISDN: The ISDN is intended to be a worldwide public telecommunications network to replace existing public telecommunications network. ISDN support of a wide range of voice and non-voice applications in same network. ISDN support a variety of applications including both switched and non-switched connection.
An ISDN will contain intelligence for the purpose of providing service features , maintenance and network management functions. ISDN will be based on the concepts for telephone IDN. ISDN support both circuit switching and packet switching.