NetIPC 3000/XL Programmer's Reference Manual (5958-8600)

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CCITT Consultative Committee
for International Telephony and
Telegraphy. An international
organization of communication
carriers, especially government
telephonemonopolies,responsible
for developing telecommunication
standards by making
recommendations. The emphasis
is on “recommendations”; no
carrier is required to adhere to a
CCITT recommendation,
although most do so in their own
interests.
closed user group An X.25 user
facility that allows
communication to and from a
pre-specified group of users and
no one else.
compatibility mode Processing
mode on HP 3000 Series 900
computers that allows
applications written for MPE
V/E-based systems to be ported
and run without changes or
recompilation.
computer network A group of
computer systems connected in
such a way that they can
exchange information and share
resources.
CUG See closed user group.
D
Datacommunications and
Terminal Controller
Transmitted data that is sent
faster than the equipment on the
receiving end is capable of
receiving it. The resulting
overflow data is lost. See also
flow control.
D bit Delivery confirmation bit.
Used in the X.25 protocol, the
setting of the D bit in DATA
packets indicates whether
delivery acknowledgment of the
packet is required from the local
DCE or from the remote DTE. It
therefore allows the choice
between local and end-to-end
acknowledgment.
DCE Data circuit-terminating
equipment. The interfacing
equipment required in order to
interface to data terminal
equipment (DTE) and its
transmission circuit. Synonyms:
data communications equipment,
dataset.
DTC Datacommunications and
Terminal Controller. The DTC is
a hardware device, configured as
a node on a LAN, that enables
asynchronous devices to access
HP 3000 Series 900 computers.
Terminals can either be directly
connected to the DTC, or they can
be remotely connected through a
Packet Assembler Disassembler
(PAD). The DTC can be
configured with DTC/X.25
Network Access cards and
DTC/X.25 Network Access
software. A DTC/X.25 XL
Network Link consists of two
software modules: the X.25 XL
System Access software (running
on the host) and the DTC/X.25
Network Access software
(running on the DTC).