Envoy ACP/XF Application Programming Manual

Glossary
EnvoyACP/XF Application Programming Manual–132179
Glossary-4
multipoint
multipoint. A data-link configuration in which one station is designated as the supervisor and
controls all communications over the link. The other stations are designated as
tributaries.
nonswitched. A line configuration that provides a permanent path between two stations. This
path can be a privately owned cable or a dedicated path leased from a common carrier. It
is generally a leased line.
NRM. Normal Response Mode. A mode of communications within the ADCCP protocol
whereby a secondary station can transmit data only after a request from the primary
station. This mode of operation is also used by SDLC.
octet. A term used with bit-synchronous frame-format, equivalent to 8 bits or 1 byte.
point-to-point. A data-link configuration between two stations. This configuration may exist
between a primary and a secondary station or between two combined stations.
primary. In an SDLC or ADCCP-NRM configuration, the primary station initiates a data
transfer and in control during the exchange of messages. It notifies each secondary link
station when it can transmit data and when it should expect to receive data. See also
secondary.
RR. Receiver Ready. A type of SDLC or ADCCP-NRM frame. This is one of the supervisory
type of frames.
RS-232. An industry standard for serial data transmission. It describes pin assignments (for a
25-pin connector), signal functions, and electrical characteristics. RS-232C is the current
standard.
RTS. Request To Send. A signal from the host computer or terminal (DTE) to the modem
(DCE) requesting permission to transmit data. Permission is granted when the modem
turns CTS to ON.
SABM. Set Asynchronous Balanced Mode. In ADCCP-ABM and HDLC, the unnumbered
frame sent by one station to establish a data link with another station.
SDLC. Synchronous Data-Link Control. The data-link layer of IBM SNA. SDLC is one of
the bit-synchronous communications protocols. It uses Normal Response Mode
operation and is analogous in many ways to ADCCP-NRM. SDLC initiates, controls,
checks, and terminates information exchanges on communications lines. It provides for
control of a single communications link or line, accommodates a number of network
arrangements, and operates in half-duplex or full-duplex over private or switched
facilities.
secondary. In an SDLC or ADCCP-NRM configuration, the secondary station is the station
that is contacted by the primary station and is controlled by the primary message in a
message exchange. The secondary station cannot initiate a communication. See also
primary.