Multi-Tech Systems MVP120 - Manual (Page 91)

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Glossary
Multi-Tech Systems, Inc. MultiVOIP User Guide
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.
Channel bank: A device that acts as a converter, taking the digital signal from the T1 line into a phone system and converting it to
the analog signals used by the phone system. A channel bank acts as a multiplexer, placing many slow-speed voice or data
transactions on a single high-speed link.
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.
Clear Channel: A transmission path where the full bandwidth is used (i.e., no bandwidth needed for signaling, carrier framing or
control bits). A 64K bps digital circuit usually has 8K bps used for signaling. ISDN has two 64K bps circuits, and a 16K bps packet
service of which part is used for signaling on the 64K channels.
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.
Cluster Controller: A device that can control the input/output operations of more than one device connected to it. A cluster
controller may be controlled by a program stored and executed in the unit, or it may be entirely controlled by hardware.
CODEC (COmpression/DEcompression): The term is used to describe the conversion of voice signals from their analog form to
digital signals acceptable to modern digital PBXs and digital transmission systems. It then converts those digital signals back to
analog so that you can hear and understand what the other person is saying. In some phone systems, the CODEC is in the PBX
and shared by many analog phone extensions. In other phone systems, the CODEC is actually in the phone. Thus the phone itself
sends out a digital signal and can, as a result, be more easily designed to accept a digital RS-232-C signal.
Committed Burst Size: The maximum number of bits that the frame relay network agrees to transfer during any measurement
interval
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.
Consecutive Severely Errored Seconds (CSES): An error condition that occurs when from 3 to 9 SES (Severely Errored
Seconds) are logged consecutively.
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
D4: the T1 4th generation channel bank.
D4 channelization: Refers to the compliance with AT&T TR 62411 for DS1 frame layout.
D4 framing: The T1 format for framing in AT&T D-Series channel banks, in which there are 12 separate 193-bit frames in a super-
frame. A D4 framing bit is used to identify the channel and the signaling frame. Signalling for voice channels is carried in-band for
every channel, along with the encoded voice. See "robbed-bit signaling".