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40 MultiModem ZPX User Guide

relay equipment that definesstatus informationexchange.

Local Loop: A transmission path, typically twisted-pair wire,

between an individual subscriber and the nearest public

telecommunications network switching center. The wires provide

ISDN service, but require an NT1 at the user end and an LT at the

network end. (AKA, “loop” or “subscriber loop”.)

Logical Link Control (LLC2): In a local area network, the protocol

that governs the exchange of transmission frames between data

stations independently of how the transmission medium is

shared. The LLC2 protocol was developed by the IEEE 802

commitee and is common to all LAN standards.

Logical Unit (LU): A type of network accessible unit that enables

end users to gain access to network resources and communicate

with each other.

Long Haul: The T1 element that connects to the Access portion

of the long distance company’s (LDC’s) central office. The LDC is

commonly called the point of presence (POP). Each LDC has a

number of POPs, located throughout the country. The LDC is also

called an IEC (Inter Exchange Carrier).

Long Haul Communications: The type of phone call reaching

outside of a local exchange (LE).

Management Information Base (MIB): A database of network

management information used by the Common Management

Information Protocol (CMIP) and the Simple Network

Management Protocol (SNMP).

Megacom: An AT&T service with a normal WATS line (typically

T1) between the customer premise and the AT&T serving class 4

CO are the customer’s responibility.

MegaLink: BellSouth’s leased T1 service.

Message: Associated with such terms as packet, frame, and

segment. 1. In information theory, an ordered series of

characters intended to convey information. 2. An assembly of

characters and sometimes control codes that is transferred as an

entry from an originator to one or more recipients.

Message Pipe: A pipe that transfers data using a request/data/

status paradigm. The data has an imposed structure which allows

requests to be reliably identified and communicated.

Modem: A communications device that enables a computer to

transmit information over a phone line. It converts the

computer’s digital signals into analog signals to send over a

phone 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.

Multiplexer (Mux): 1. A device that takes several input signals

and combines them into a single output signal in such a manner

that each of the input signals can be recovered. 2. A device

capable of interleaving the events of two or more activities or

capable of distributing the events of an interleaved sequence to

the respective activities. 3. Putting multiple signals on a single

channel.

Multiprotocol: A device that can interoperate with devices

utilizing different network protocols.

Multithreading: The ability of a software system to be able to

handle more than one transaction concurrently. This is

contrasted to the case where a single transaction is accepted and

completely processed befor the next transaction processing is

started.

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.

Node: Any point within a network which has been assigned an

address.

OHCI (OpenHCI): Open Host Controller Interface Specification for

USB. All transfers on the USB are initiated by the host system’s

host controller. The host controller is responsible for controlling

traffic on the USB and can be appropriately programmed to

transfer data to and from USB devices. This is typically a PCI

device that can be programmed to run a given schedule of

transfers on the USB and bus master the results into memory for

processing by the host software. There are currently two standards

forhost controllers: OpenHCI (OHCI or Open Host Controller

Interface) and UHCI (UniversalHostController Interface). Both

these standardsdefine register level interfaces of the host

controller to PCI bus. Bandwidth allocation over the USB is software

managed and is done by the programming of the host controller.

Object-Oriented: A method for structuring programsas

hierarchically organized classes describing the data and

operations of objects that may interact with other objects.

Office Channel Unit - Data Port (OCU-DP): The CO channel bank

used as the interface between the customer’s DSU and the

channel bank.

Off-hook: The condition of a device which has accessed a phone

line (with or without using the line). In modem use, this is

equivalent to a phone handset being picked up. Dialing and

transmission are allowed, but incoming calls are not answered.

Contrast “on-hook”.

Off Premise Extension (OPX): An extension or phone that

terminates in a location other than that of the PBX. Commonly

used to provide a corporate member with an extension of the

PBX at home.

Ones Density: The measure of the number of logical 1s on a T1

line compared to a given total number of bits on that line; used

for timing information in data recovery in AMI and B8ZS.

On-Hook: The condition of a device which has not accessed a

phone line. In modem use, this is equivalent to a telephone

handset that has not been picked up. In other words, it can

receive an incoming call. Contrast “off-hook”.

Open Shortest Path First (OSPF): A hierarchical Interior Gateway

Protocol (IGP) routing algorithm for IP that is a proposed

standard for the Internet. OSPF incorporates least-cost routing,

equal-cost routing, and load balancing.

Outage: The measure of the time during which a circuit is not

available for use due to service interrupt. Outage is the

complement of circuit “availability” (100% minus % available = %

outage).

Out-of-band: Signaling that is separated from the channel

carrying the information (e.g., the voice/data/video signal is

separate from the carrier signal). Dialing and various other

“supervisory” signals are included in the signaling element.

Contrast “In-band” signaling.

Out of Frame (OOF): A T1 alarm condition that is logged on the

loss of 2, 3 or 4 of 5 consecutive FT framing bits.

Glossary

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