Multitech PROXYSERVER MTPSR1-120 Guía de usuario descargar pdf (Pagina 68)

Firewall 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.

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.

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.

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