frame relay This ANSI/ITU-T-standard packet interface protocol has a few advantages over ISDN. For one thing, you can purchase frame relay lines in increments between 56 kbps and 1.5 mbps (equivalent to a T1 connection). The protocol also has a flat-rate billing structure instead of a per-hour usage charge. But frame relay is designed for data transfer only, so it's not well suited to videoconferencing or any other voice application. Frame relay is sometimes confused with a leased line. Both are used primarily to extend a local area network (LAN) between business branches. However, a leased line is a dedicated line permanently connected between sites, and frame relay uses the telephone company's shared network on an as-needed basis.