Multitech RouteFinder MTASR2-203, User Manual, Page: 78 / 90

RouteFinder-T1 User Guide
MTASR2-203 78
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.
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.
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
managemennt 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 telephone 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”.
Data Communications Equipment (DCE): Any device which serves as the portal of entry from the user equipment to a
telecommunications facility. A modem is a DCE for the telephone 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.