Appendix C: WAN Terms and Acronyms
C-2 HSIM-W87 User’s Guide
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 DSX-1 interface on the CPE.
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
WPIM-DI which allows the user to map timeslots that are not being used
to another WAN device.
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 RS-232 or other terminal
interfaces to DSX-1 (T1) interface.
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.
