FDDI is a set of ANSI protocols for sending digital data over fiber optic cables. A fiber optic cable consists of a bundle of threads, each of which is capable of transmitting messages modulated onto light waves. Compared to metal cables, fiber optics are more brittle, but they are carry more data, are less prone to interference, and are lighter. Fractional T1 One of the 24 channels that comprise a full T1 data line. Fractional T1 lines can usually be leased individually.
Frame relay is faster than earlier protocols because it omits flow control and error correction.
A communications system or channel capable of simultaneous transmission in two directions. HDLC High-level Data Link Control. Frame relay is an example of an HDLC-based packet protocol. HSSI High-Speed Serial Interface. HSSI is a short-distance communications interface that achieves data rates up to 52 Mbps.