X25AM Programming Manual

Glossary
X25AM Programming Manual—527201-001
Glossary-5
ITI protocol.
ITI protocol. Interactive terminal Interface protocol. For X25AM, it is used by the X25AM
process when an application exchanges data with a remote terminal connected to an
X.25 packet-switching network with a PAD.
LAP. See Link Access Procedure and Link Access Procedure in a Balanced System (LAP
and LAPB).
LAPB. See Link Access Procedure and Link Access Procedure in a Balanced System (LAP
and LAPB).
leased line. Telephone line reserved for exclusive (private) use of the leasing customer
link. Call or transmission path (including all equipment) between a sender and receiver.
Link Access Procedure and Link Access Procedure in a Balanced System (LAP and
LAPB). Procedures used in a packet-switching network for data interchange across
the access link between a network and the computers, terminals, or other devices.
Responsible for activities involving framing, synchronization control, and error
detection.
link layer. See frame layer.
LIU. Line Interface Unit. Interfaces with a CIU in a controller and supports a single
communications line. 6101 and 6110 controllers can have 1 through 15 LIUs. The 3605
and 6105 controllers can have 4 LIUs.
logical channel. Means of two-way communications between two network entities.
logical channel number. Number assigned to a logical channel to uniquely identify it.
logical device. Device that can be accessed and addressed. It may not be equivalent to a
physical device.
low PIN. A PIN that ranges from 0 through 254. See alsohigh PIN.
MCW. Message control word. First two bytes (one word) of a message in the application
buffer; it contains message control information. Used in a user-coded program utilizing
the PTP application protocol.
message. Complete communications sent as a unit, able to be queued and assigned
priorities.
modem. Modulator Demodulator. Hardware that converts digital data to an analog signal
for transmission over a telephone channel, or vice versa.
modem eliminator. Device that allows data communications equipment to be connected
without modems and telephone lines.
modulo. A repeating packet-numbering sequence.