X25AM Configuration and Management Manual

Glossary
X25AM Configuration and Management Manual—523424-004
Glossary-4
EBCDIC
EBCDIC. Extended binary-coded decimal interchange code. Standard method of coding
data, consisting of 8 bits of data with no parity bit for each character.
fast select. Optional network facility allowing call setup packets to contain a call user data
(CUD) field of up to 128 octets.
flow control. Mechanism by which the recipient of incoming data notifies the sender to stop
or start transmitting data depending on the state (full or empty) of the recipient’s
incoming data buffer.
frame. Message unit that consists of a sequence of bits bracketed by beginning and ending
flag sequences. It can contain packets.
frame layer. Also called the link level. It is the X.25 protocol description for the link access
procedures for the link between the network and the computers, terminals, or other
devices.
FRMR. Frame Reject. A response frame indicating the receipt of an invalid frame format,
invalid command, or invalid response.
full-duplex. Method of serial communications in which the data flow between two points can
occur in both directions simultaneously.
half-duplex. Method of serial communications in which the data flow between two points
can occur in only one direction at a time.
hex. Hexadecimal. Base-16 numbering system.
I-frame. Information frame. Link-level frame that contains a packet.
incoming call packet. Packet that the network sends to a remote entity in response to
receiving a call request packet addressed to that entity.
interface. Shared boundary defined by common interconnection characteristics.
International Organization for Standardization (ISO). International Organization for
Standardization. ISO is an international body that drafts, discusses, proposes, and
specifies standards for network protocols. ISO is best known for its seven-layer
reference model that describes the conceptual organization of protocols.
interrupt. Signal used by a device to stop the current task of a subordinate device. Once
stopped, the subordinate device waits for the primary device to send information to it.
invitation-to-clear packet. Sometimes sent as the last data packet or after the last data
packet to request the disconnection of the call, to solve the problem of having a clear
packet overtake a data packet (causing a call to be disconnected before all of the data
is received).