3Com Courier Reference

Contents

3Com Courier Reference Manual pdf 199 page image

G LOSSARY 9Nonvolatile RandomAccess Memory(NVRAM)User-programmable random access memory whose data is retainedwhen modem power is turned off. Used in Courier V.Everythingmodems to store a user-defined default configuration loaded intorandom access memory (RAM) at power onNVRAM See Non-volatile Random Access Memory.online fallbac A feature that allows high speed error-control modems to monitor linequality and fall back to the next lower speed if line quality degrades.The modems fall forward as line quality improves.originate mode A state in which the modem transmits at the predefined low frequencyof the communications channel and receives at the high frequency. Thetransmit/receive frequencies are the reverse of the called modem whichis in Answer mode.parallel transmission The transfer of data characters using parallel electrical paths for eachbit of the character, for example, 8 paths for 8-bit characters. Data isstored in computers in parallel form, but may be converted to serialform for certain operations. See Serial Transmissionparity An error-detection method that checks the validity of a transmittedcharacter. Character checking has been surpassed by more reliable andefficient forms of block-checking, including Xmodem-type protocolsand the ARQ protocol implemented in Courier V.Everything modems.The same type of parity must be used by two communicatingcomputers, or both may omit parity. When parity is used, a parity bit isadded to each transmitted character. The bit's value is 0 or 1, to makethe total number of 1's in the character even or odd, depending onwhich type of parity is used.Point-to-PointProtocol (PPP)A protocol used to send data over serial lines. PPP provides errorchecking, link control, and authentication, and can be used to carry IP,IPX, and other protocols. PPP is superseding SLIP as the leading dial-inprotocol.protocol A system of rules and procedures governing communications betweetwo or more devices. Protocols vary, but communicating devices mustfollow the same protocol in order to exchange data. The format of thedata, readiness to receive or send, error detection and error correctionare some of the operations that may be defined in protocols.provisioning Another way of saying "setting up telephone lines."