User guide

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Glossary
Multi-Tech Systems, Inc. MultiVOIP User Guide
Byte: The unit of information a computer can handle at one time. The most common understanding is that a byte consists of 8
binary digits (bits), because that's what computers can handle. A byte holds the equivalent of a single character (such as the letter
A).
C
Call Setup Time: The time to establish a circuit-switched call between two points. Includes dialing, wait time, and CO/long distance
service movement time.
Carrier signal: An analog signal with known frequency, amplitude and phase characteristics used as a transport facility for useful
information. By knowing the original characteristics, a receiver can interpret any changes as modulations, and thereby recover the
information.
CCITT (Consultative Committee for International Telephone and Telegraph): An advisory committee created and controlled by
the United Nations and headquartered in Geneva whose purpose is to develop and to publish recommendations for worldwide
standardization of telecommunications devices. CCITT has developed modem standards that are adapted primarily by PTT (post,
telephone and telegraph) organizations that operate telephone networks of countries outside of the U.S. See also ITU.
Central Office (CO): The lowest, or most basic level of switching in the PSTN (public switched telephone network). A business
PABX or any residential phone connects to the PSTN at a central office.
Centrex: A multi-line service offered by operating telcos which provides, from the telco CO, functions and features comparable to
those of a PBX for large business users. See also "Private Branch Exchange", "Exchange".
Channel: A data communications path between two computer devices. Can refer to a physical medium (e.g., UTP or coax), or to a
specific carrier frequency.
Circuit-switched Network: A technology used by the PSTN that allocates a pair of conductors for the exclusive use of one
communication path. Circuit switching allows multiple conversations on one talk path only if the end-users multiplex the signals prior
to transmission.
Circuit switching: The temporary connection of two or more communications channels using a fixed, non-shareable path through
the network. Users have full use of the circuit until the connection is terminated.
Client-Server: In TCP/IP, the model of interaction in distributed data processing in which a program at one site sends a request to
a program at another site and awaits a response. The requesting program is called a client; the answering program is called a
server.
Committed Information Rate (CIR): An agreement a customer makes to use a certain minimum data transmission rate (in bps).
The CIR is part of the frame relay service monthly billing, along with actual usage, that users pay to their frame relay service
provider.
Compression: 1. The process of eliminating gaps, empty fields, redundancies, and unnecessary data to shorten the length of
records or blocks. 2. In SNA, the replacement of a string of up to 64-repeated characters by an encoded control byte to reduce the
length of the data stream to the LU-LU session partner. The encoded control byte is followed by the character that was repeated
(unless that character is the prime compression character). 3. In Data Facility Hierarchical Storage Manager, the process of moving
data instead of allocated space during migration and recall in order to release unused space. 4. Contrast with decompression.
COMx Port: A serial communications port on a PC.
Congestion: A network condition where there is too much data traffic. The ITU I.233 standard defines congestion management in
terms of speed and burstiness.
Congestion notification: The function in frame relay that ensures that user data transmitted at a rate higher than the CIR are
allowed to slow down to the rate of the available network bandwidth.
Customer Premise Equipment (CPE): The generic term for data comm and/or terminal equipment that resides at the user site
and is owned by the user with the following exclusions: Over voltage protection equipment, inside wiring, coin operated or pay
telephones, "company-official" equipment, mobile phone equipment, "911" equipment, equipment necessary for the provision of
communications for national defense, or multiplexing equipment used to deliver multiple channels to the customer.
D
Data Communications Equipment (DCE): Any device which serves as the portal of entry from the user equipment to a telecom-
munications facility. A modem is a DCE for the phone network (PSTN) that is commonly on site at the user’s premises. Packet
Switched Networks have another level of DCE which is most often located at a central office.
Data Service Unit (DSU): A device that provides a digital data service interface directly to the data terminal equipment. The DSU
provides loop equalization, remote and local testing capabilities, and a standard EIA/CCITT interface.
Default: This is a preset value or option in software packages, or in hardware configuration, that is used unless you specify
otherwise.
Device driver: Software that controls how a computer communicates with a device, such as a printer or mouse.