Connect Tech Echo/ISA Uživatelská příručka stáhnout pdf (Strana 39)

MultiModem ZPX User Guide 39

central office provides the point of reference for T1 access. Any

common carrierauthorized by the FCC to carry customer

transmissions between LATAs.

Internet: Refers to the computer network of many millions of

university, government and private users around the world. Each

user has a unique Internet Address.

Internet Address (IP Address): A unique 32-bit address for a

specific TCP/IP host on a network. Normally printed in dotted

decimal format (e.g., 129.128.44.227).

Internet Protocol (IP): A protocol used to route data from its

source to its destination in an Internet enviroment. The Internet

Protocol was designed to connect local area networks. Although

there are many protocols that do this, IP refers to the global

system of interconnecting computers. It is a highly distributed

protocol (each machine only worries about sending data to the

next step in the route).

Internetwork Packet Exchange (IPX): A NetWare communications

protocol used to route messagesfrom one node to another. IPX

packetsincludenetwork addresses andcanberouted from one

network to another. An IPX packet can occasionally get lost when

crossing networks, thus IPX does not guarantee delivery of a

complete message. Either the application hasto provide that

control, or NetWare’s SPX protocol must be used.

Interoperable: Devices from differentvendors thatcan exchange

information using a standard’s base protocol.

Interrupt Request: A hardware signal that allows a device to

request attention from a host. The host typically invokes an

interrupt service routine to handle the condition which caused

the request.

I/O Addresses: Locations within the I/O address space of your

computer used by a device, such as an expansion card, a serial

port, or an internal modem. The address is used for

communication between software and a device.

IRQ Level (Interrupt Request Level): The notification a processor

receives when another portion of the computer’s hardware

requires its attention. IRQs are numbered so that the device

issuing the IRQ can be identified, and so IRQs can be prioritized.

Isochronous data: Information delivered in a continuous stream

at a steady rate.

ISA (Industry Standards Architecture) (pronounced “ice a”): The

classic 8 or 16-bit architecture introduced with IBM’s PC-AT

computer.

ISDN (Integrated Services Digital Network): An International

telecommunications standard for transmitting voice, video and

data over a digital communications line. ISDN is a world-wide

telecommunications service that uses digital transmission and

switching technology to support voice and digital data

communications. Frame relay was partially based on ISDN’s data

link layer protocol (LAPD). Frame relay can be used to transmit

across ISDN services offering circuit-switched connection at 64

Kbps and higher speeds. Contrast Public Switched Telephone

Network (PSTN).

ITU-TSS (formerly CCITT): International Telecommunications

Union-Telecommunications Sector; the United Nations

organization that prepares standards (“Recommendations”) for

resolving communications issues and problems.

Key Telephone System (KTS): Phone devices with multiple buttons

that let you select incoming or outgoing CO phonelines directly.

Similar in operation to a PBX, except with a KTS you don’t have to

dial a “9” to call outside the building.

Key Service Unit (KSU): A small device containing the switching

electronics for a business key telephone system (KTS).

Key Set: A phone set with several buttons for call holding, line

pickup, intercom, autodialing, etc. Also called a touchtone phone

(Ericsson) and a KTS (Key Telephone Set).

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

establishes and maintains communications between the DTE and

the DCE.

LAPD: LinkAccess 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 called “frames”,

and a frame may contain one or more X.25 packets.

Line Coding: The representation of 1s and 0s on a T1 line. The

two methods of line coding commonly used, B8ZS and AMI,

differ in the restrictions placed on user data. T1 line coding

ensures that sufficient timing information is sent with the digital

signal to ensure recovery of all the bits at the far end. Timing

information on the T1 line is included in the form of 1s in the

data stream; a long string of 0s in the data stream could cause

problems recovering the data.

Line Termination (LT): The electronics at the ISDN network side

of the user/network interface that complements the NT1 at the

user side. The LT and the NT1 together provide the high-speed

digital line signals required for BRI access.

Listed Directory Number (LDN): The main number assigned by

the telco; the number listed in the phone directory and also

provided by Directory Assistance. Some devices can have more

than one LDN, such as ISDN devices that have one LDN for voice

and another LDN for data.

Local Area Network (LAN): 1. A computer network located on a

user’s premises within a limited geographical area.

Communication within a local area network is not subject to

external regulations; however, communication across the LAN

boundary may be subject to some form of regulation. 2. A LAN

does not use store-and-forward techniques. 3. A network in

which a set of devices are connected to one another for a

communication and that can be connected to a larger network.

Local Access and Transport Area (LATA): A post-divestiture

geographical area generally equivalent to a Standard

Metropolitan Statistical Area. At divestiture, the territory served

by the Bell system was divided into approximately 161 LATAs.

The Bell Operating Companies (BOCs) provide Intra-LATA

services.

Local Exchange Carrier (LEC): The local phone company which

provides local (i.e., not long distance) transmission services. AKA

“telco”. LECs provide T1 or FT1 access to LDCs (unless the T1

circuit is completely intra-LATA). Inter-LATA T1 circuits are made

up of a combination of Access and Long Haul facilities.

Local Management Interface (LMI): A specification for frame

Glossary

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