Definition: SMDS

(Switched Multimegabit Data Service) A high-speed, switched data communications service offered by the local telephone companies for interconnecting LANs in different locations. It was introduced in 1992 and became generally available nationwide by 1995.

Connection to an SMDS service can be made from a variety of devices, including bridges, routers, CSU/DSUs as well as via frame relay and ATM networks. SMDS can employ various networking technologies. Early implementations use the IEEE 802.6 DQDB MAN technology at rates up to 45 Mbps.

Data are framed for transmission using the SMDS Interface Protocol (SIP), which packages data as Level 3 Protocol Data Units (L3_PDU). The L3_PDU contains source and destination addresses and a data field that holds up to 9188 bytes.