connectionless broadband data service (MAN) (CBDS)
Connectionless Broadband Data Service (CBDS) is a connectionless datagram service for interconnecting local area networks( LAN).
CBDS is the European counterpart to the American Switched Multimegabit Data Service( SMDS) developed by Bellcore. It is a cell-oriented transport protocol for city networks( MAN), based on IEEE 802.6.
The layer model of CBDS is defined in ETSI-300211 and, like the SMDS layer model, is structured in three layers. On the physical layer, Layer 1, there is a dual bus concept for MANs with Distributed Queue Dual Bus( DQDB). Layer 2 is supported by Service Management Protocol Data Units (SMPDU) and Layer 3 by Initial MAC PDUs (IMPDU). E- transmission interfaces for the physical layer are defined by ETSI as 2.048 Mbit/s for the E1 line and 34.368 Mbit/s for E3.