Appendix C: WAN Terms and Acronyms
BRI — Basic Rate Interface, minimum rate ISDN subscriber interface, provides 2 B + 1 D channels (two 64 Kbps “B” (Bearer) channels and one 16 Kbps “D” (Data) signaling channel for a total of 144 Kbps).
BRIM — Cabletron Systems Bridge Router Interface Module. Expands the physical connectivity of a host platform.
CPE — Customer Premises Equipment.
CRC — Cyclic Redundancy Check, an algorithm or process used to identify corrupted packets in the transmission link.
CSU — Channel Service Unit, a device that terminates the local loop/digital channel on a customer’s (DSU) premises. The CSU connects to a
DCE — Data Communications Equipment, a device such as a modem that connects the communications circuit with the end device (see DTE).
CPE — Customer Premises Equipment, Telecommunications equipment on the customer site, such as CSU/DSUs, PBXs, etc., that reside past the network interface.
Data (D) Channel — A 16 Kbps channel used with BRI and PRI services for signaling and control.
D4 — D4 Framing, a popular framing format in T1. Uses 12 T1 Frames to identify both the channel and the signaling bit.
DI — Drop and Insert, a function provided on the Cabletron Systems
DLCI — Data Link Connection Identifier, a unique virtual circuit identifier used in Frame Relay. Identifies a given frame as being from a particular logical link. The DLCI has only local significance.
DSU — Digital Service Unit, converts
DS0 — Digital Signal, level 0, a standard 64,000 bit/second channel. Synonymous with “Timeslot.”
DS1 — Digital Signal level one, the rate of transmission for a T1 line, running at 1.544 Mbps.
DS3 — 28 T1s.
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