X25AM Programming Manual

Glossary
X25AM Programming Manual—527201-001
Glossary-2
call setup.
call setup. Descriptive phrase for the activities required to establish a virtual circuit,
involving call request, incoming call, call accepted, and call connected packets.
Data transmission between the caller and the remote entity can begin after the
circuit is established.
called address. Network address of a remote device or system (the entity being called).
calling address. Network address of a local device or system (the entity making the call).
call user data (CUD). Field appearing only in Call Setup packets, such as Call Request
and Incoming Call, and in Fast Select packets. Maximum of 16 bytes, depending on
the protocol configured for the particular subdevice. See also User data.
CCITT. Comité Consultatif International Télégraphique et Téléphonique (International
Telegraph and Telephone Consultative Committee). Standards-setting group for
international telephone carriers.
channel. A path over which data and messages are sent.
character. Letter, figure, number, punctuation mark, or other symbol contained in a
message or used in a control function.
circuit. Means of two-way communications between two network entities.
CIU. Communications Interface Unit. Each 3650/6100 family controller has a physical or
logical pair of CIUs. A CIU is responsible for interfacing between the main controller
logic and the line control unit (LIU).
clear-indication packet. Packet sent by the network when a call is disconnected.
clear-confirmation packet. Packet sent by the network to the caller when a call has been
disconnected in response to the caller request to disconnect.
clear-request packet. Packet sent by the caller to disconnect the call clock. In
synchronous transmission, the source for timing signals.
CMI. Communications Management Interface. A subsystem used for issuing configuration
and information requests between the user and some communications subsystems.
common carrier. Company that furnishes communications services to the public and is
regulated by appropriate state or federal agencies.
Communications Management Interface. See CMI.
communications subsystem. Collection of hardware and software that provides a specific
communications function (for example, communications between NonStop system and
an X.25 network).
conversation mode. Data transmission mode for a terminal. Transmitted data messages
consist of single characters instead of groups of characters.