Glossary- Z
A Data Communication Historical Series
By Bob Pollard

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ZBTSI;

See Zero Byte Time Slot Interchange

ZERO SUPPRESSION:

The elimination of unimportant zeros in a data stream

ZERO BIT INSERTION:

A technique used to achieve transparency in bit-oriented protocols. A zero is inserted into a sequence of one bits that causes a false flag direction. Synonym: bit stuffing

ZERO BYTE TIME SLOT INTERCHANGE (ZBTSI):

A technique used to ensure pulse density for increase channel capability.

ZERO CODE SUPPRESSION:

The practice of suppressing the transmission of eight of more consecutive binary 0 bits by inserting a binary 1 bit: Zero code suppression is used with digital T1 and related communications facilities. Line coding scheme used for transmission clocking. Zero line suppression substitutes a 1 in the 7th bit of a string of eight consecutive zeros.

ZERO INSERTION:

A practice used in an SDLC environment that includes a binary 0 in a stream of transmitted data to avoid confusing SYN characters with data characters. The receiving end removes the inserted zeros.

ZERO TRANSMISSION LEVEL POINT:

A point of reference (0 TLP) used to measure signal power gain/loss of a data circuit.

ZIP:

Zone Information Protocol: AppleTalk session layer protocol that maps network numbers to zone names. ZIP is used by NBP to determine which networks contain nodes that belong to a zone;

A standard for compression and decompression used widely for PC download processes.

ZIP FILE:

ZIP Archive File: A ZIP archive contains compressed collections of other files. ZIP files are popular on the Internet because users can deliver multiple files in a single container; the compressed files also save disk space and download time. A ZIP file can contain viruses if any of the files packaged in it contain viruses, but the ZIP file itself is not directly dangerous. Other archive files include RAR, and LHA files. This file type has the extension ZIP.

ZIP STORM:

Broadcast storm that occurs when a router running AppleTalk propagates a route for which it currently has no corresponding zone name. The route is then forwarded by downstream routers, and a ZIP storm ensues.

ZMODEM:

A streaming protocol facility: Offering higher efficiency than XMODEM or YMODEM.

ZONE:

1) Collection of all terminals, gateways, and multipoint control units (MCU) managed by a single gatekeeper. A zone includes at least one terminal, and can include gateways or MCU(s). A zone has only one gatekeeper. A zone can be independent of LAN topology and can be comprised of multiple LAN segments connected using routers or other devices.

2). In AppleTalk, a logical group of network devices.

ZONE MULTICAST ADDRESS:

Data-link-dependent multicast address at which a node receives the NBP broadcasts directed to its zone.

ZONE PREFIX:

A prefix that identifies the addresses to be serviced by a given gatekeeper: Zone prefixes are typically area codes and serve the same purpose as the domain names in the H.323-ID address space.

ZONING:

Several devices are grouped by function or by location. All devices connected to a connectivity product may include configuration of one or more zones. Devices in the same zone can see each other; devices in different zones cannot.

ZOO / ZOO VIRUS:

A collection of viruses used for testing by researchers. A zoo virus exists in the collections of researchers and has never infected a real world computer system.

Z39.50:

American National Standard Z39.50: Information Retrieval Service Definition and Protocol Specification for Library Applications." This was designed to be a standard for connecting library computers and databases regardless of hardware and software. It could be used as a standard for many kinds of databases. There are many other database protocols in use today in and out of libraries.

ZULU DATE:

The day (date) at Greenwich, England

ZULU TIME:

Longitude Zero or Greenwich, England Mean Time (GMT): Zulu time (GMT) is always the same worldwide. Communications networks use Zulu Time for coordination.