Multi Tech Equipment MTA128ST - Manual (Page 56)

Glossary
MTA128ST/NT 56
organization that prepares standards for resolving
communications issues and problems.
L
LAPB (Link Access Procedure Balanced)—Based
on the X.25 Layer 2 specification. A full-duplex, point-
to-point, bit-synchronous protocol commonly used as a
data link control protocol to interface X.25 DTEs.
LAPB is the link initialization procedure that estab-
lishes and maintains communications between the
DTE and the DCE.
LAPD
(Link Access Protocol for the
D-Channel)—Based on the ISDN Q.921 specification.
A full-duplex point-to-point bit-synchronous link-level
protocol for ISDN connections; different from LAPB in
its framing sequence. Transmission is in units
calledframes, and a frame may contain one or more
X.25
packets.
link optimization
—An ISDN feature that permits only
user data to open the communications link and
keeps administrative packets from opening the link. A
cost saving feature that ensures that remote
connections are not unnecessarily utilized.
local loop —A transmission path, typically twisted-
pair wire, between an individual subscriber and the
nearest public telecommunications network switching
center. Also called the subscriber loop.
LT
(loop termination)—A device, similar to an NT1,
that terminates the local loop at the carrier’s central
switching office. The LT provides the interface to the
ISDN U reference point. Contrast ET (exchange
termination).
M
MD5 (MD5 Message-Digest Algorithm)—Takes a
message if arbitrary length as input and produces it
as output as a 128-bit fingerprint or message digest
of the input. The MD5 algorithm is used for digital
signature applications where a large file must be
compressed in a secure manner before being
encrypted with a private (secret) key under
public-key cryptisystem.
MLPPP (Multilink Point-to-Point Protocol, also the
PPPMultilink Protocol or MP)—is an Internet
standards track protocol for a methyod of splittingm
recombining, and sequencing datagrams across
multiple logical data links, giving you additional
bandwithon-demand. Originally, MLPPP was used to
combine two ISDN BRI channels into a single high-
speed data path, but now is also used anywhere
multiple PPP links connect two systems, including
async links. This is done with new PPP options and
protocols. Also knows as MPPP and PPP Multilink,
MLPPP is an effective means of bonding channels for
providing bandwith-on-demand.
modem —A communications device that enables a
computer to transmit information over a telephone
line. It converts the computer’s digital signals into
analog signals to send over a telephone line and
converts them back to digital signals at the receiving
end. Modems can be internal and fit into an
expansion slot, or external and connect to a serial
port.
MP+ (MultiLink Protocol Plus)—An extension to the PPP
Multilink Protocol (MP) convered in IETF RFC 1717. MP+ is a
new control protocol for managing multiple data links that are
bundled by MP. Also called the Multichannel Protocol Plus
or MPP.
MS-CHAP —Microsoft version of CHAP.
multilink —In point-to-point protocol, literally many links. A
procedure used to route data packets over many links for
increased bandwidth (e.g., two B-channels on a single BRI
for 128 Kbps).
mux (multiplexer)—A device that merges several signals into
one composite signal for transmission over a single medium
or channel. A demultiplexer, built into most muxes, reverses
the process at the receiving end.
N
nailed connection
—A permanent or dedicated circuit of a
previously switched circuit or circuits.
nailed-up circuit —A semi-permanent circuit established
through a circuit-switching facility for point-to-point
connectivity.
NAK
(negative acknowledgment)—A communications code
used to indicate that a message was not properly received, or
that a terminal does not wish to transmit. Contrast with ACK.
network —A group of computers connected by cables or
other means and using software that enables them to
share equipment, such as printers and disk drives to
exchange information.
NI-1 (National ISDN-1)—A physical standard to make all
compliant ISDN lines appear the same. With ISDN-1
installed, additional costs are not incurred when changing
from prestandard ISDN to standard ISDN. Most RBOCs now
are moving to ISDN-1.
NI-2 (National ISDN-2)—A physical standard subsequent to
NI1. When tested and deployed, NI-2 will provide additional
features and enhanced plug and play capabilities.
node
—Any point within a network that has been
assigned an address.
NT (network termination)—Devices that form the boundary
between customer premise equipment and telephone
company equipment. Two types of NTs are used: NT1 and
NT2.
NT1 (Network TerminationType 1)—An interface device used
in the BRI portion of ISDN to connect four-wire (S/T) ISDN
devices to the two-wire (2BIQ U) IDN. It provides basic rate
access in a 2B+D format with two 64 bps channels for voice,
data, and video communications. It also provides one 16 Kbps
channel for packet-mode signalling, low-speed data and
telecommunications services at the OSI Layer 1 level.
Similar in function to a DSU/CSU device. NT2 (Network
TerminationType 2)—A device at the customer premise
(user) side responsible for the ISDN network connection and
for functions such as multiplexing and switching (may be an
intelligent device).
NTE (network terminating equipment)—A set of ISDN
functions residing at the boundary of the IDN and the
subscriber.
NUI
(network user identification)—A unique alphanumeric
number provided to dial-up users to identify them to packet-
switched networks world-wide. The number is used for
network access and billing.
O