For a local area network (LAN), CDDI (Copper Distributed Data Interface) is a standard for data transmission based on FDDI (Fiber Distributed Data Interface) that uses shielded twisted-pair (STP) or unshielded twisted pair (UTP) copper wire instead of fiber optic lines. CDDI supports a dual-ring capacity of 200 Mbps. CDDI's maximum distance is up to 200 meters, which is much shorter than FDDI.Content Continues Below
CDDI is defined by the American National Standards Committee X3-T9.5 and conforms to the Open Systems Interconnection (OSI) model of functional layering. CDDI is officially named the Twisted-Pair Physical Medium Dependent (TP-PMD) standard and is also referred to as Twisted Pair Distributed Data Interface (TP-DDI).