WAN Terms and Acronyms
HSIM-W87 User’s Guide C-5
PLB — Payload Loop Back, ESF loopback including the facilities
datalink.
Point of Presence — The point between the carrier provided equipment
and services and the customer provided equipment and services.
PPP — Point-to-Point Protocol, provides a method for transmitting
datagrams over serial point-to-point links.
PRI — Primary Rate Interface, an ISDN service providing 23 “B”
(Bearer) channels of 64 Kbps and one 64 Kbps “D” (Data) channel for
signaling and control.
PVC — Permanent Virtual Circuit, a virtual circuit that provides the
equivalent of a dedicated private line service.
Q.933-A — Q.933 Annex A, an ITU link management protocol
specification used in Frame Relay.
RAI — Remote Alarm Indicator, is declared in C-bit Parity DS3
applications, after detecting the Yellow Alarm Signal on the alarm
channel.
SDLC — Synchronous Data Link Control, layer 2 (link layer) protocol
developed by IBM for SNA connectivity. Basis for HDLC.
SEFS — Severely Errored Framing Seconds, is a second with one or
more OOF errors or a detected incoming AIS.
SNA — Systems Network Architecture, data communication network
architecture developed by IBM in the 1970’s.
T1 — A Bell System term that refers to the physical carrier, or system of
transmission media and regenerators, used to transmit a digital signal at
1.544 Mbps.
T1.617-D — T1.617 Annex D, an ANSI link management protocol
specification used in Frame Relay.
TDM — Time Division Multiplexing, a technique in which separate data
or voice signals are transmitted simultaneously over a single
communications medium based on time interleaving.
Timeslot — A standard 64,000 bit/second channel. Synonymous with
DS0 (Digital Signal, level 0).
