Last November, I received an e–mail from my editor, Tom Kenny saying “…We have a feature on network storage systems that we’re trying to figger out (so) what we’d like from you, if you agree, is a glossary of common storage and network terms. An IT glossary for the uninitiated pro audio folks. Whammy think? A whole column of pedants in a box.” So began this month’s Bitstream, a bass ackwards version of my usual offering.
Granted, I could never compete with the many excellent IT glossaries out there on the web but, I’ve tried to gather the most common TLAs, techie phrases and geek–speak for your edification. For those who need a bit of a mental housecleaning, this month will either sweep away some cobwebs or increase the BBF by several orders of magnitude!
Part One of Pedants In A Big Box was published in March of 2004. Note that bold words have their own definitions in this glossary…
Dolby Digital —
See AC-3.
Domain Name —
Domain names are the human–readable names that uniquely identify a web site. Domain names are composed of two parts; the second–level domain name and its TLD separated by a “dot” or period. In my case, my second–level domain name is seneschal and its TLD is “net,” resulting in the complete domain name, <seneschal.net>. Domain names are mapped to a particular server via DNS.
Downtime —
Downtime, the opposite of uptime, refers to the amount or percentage of time that a product, system or service is operational.
DNS — Domain Name Service, Domain Name System
DNS is used to describe two related processes, the Domain Name System and domain name services based on that system. The Domain Name System is a distributed hierarchical database that maps domain names, such as <www.seneschal.net> to their corresponding IP addresses which, in seneschal.net’s case, is <216.183.98.5>. The Domain Name Services are simply servers whose “job” it is to provide name resolution to its connected network.
DSn — Data Service (level 0, 1, 2, etc.)
Originally denoting the data rate necessary to carry a single digitized (PCM) voice, DS-0 (zero) has come to mean a 64 kbaud data service. DS1, at 1.544 Mbps, can carry 24 TDM–multiplexed streams and DS2 carries 4 DS1 loads. At a DS3 level, 672 individual calls can pass down the same “pipe.”
DSL — Digital Subscriber Line
DSL is a technology that overlays data services on POTS. DSL is available in several tiers including symmetrical (SDSL) and asymmetrical (ADSL) service at a variety of data rates, with and without QoS guarantees.
DTS — Digital Theater Systems
Originally designed for motion picture soundtracks, DTS’ lossy codecs compete with Dolby Lab.s for consumer mind share.
DTV — Digital Television
A mess created by a lack of will on the part of appointed officials and outlandish lobbying by broadcasting special interests.
DWDM — Dense Wave Division Multiplexing
DWDM is frequency–domain multiplexing in the optical domain, whereby thousands of digitized streams are imposed on different frequencies or colors of laser light and launched simultaneously down an optical fibre. Frequency discriminating detectors at the destination sort out each carrier color and decode the data. DWDM is used by telecoms to dramatically increase the payload capacity of in–place fibre.
encryption —
The process of converting information from an open form to a closed, secret form requiring hidden knowledge to convert the data back into the open form. AES is an example of a standard method of encryption.
ethernet —
A LAN method, first described in 1973, that has become as ubiquitous and adaptable as computers themselves. A “broadcast computer communications network” originally invented at Xerox PARC by Bob Metcalfe and his team, Ethernet has managed to prosper and evolve over a 30 year life span, an eternity by any measure of computer technology.
error correction —
Error correction is the process that follows error detection, whereby the original data is recovered after some impairment.
error detection —
Error detection refers to the ability to detect corruption in a set of data. Metadata is often included in a file, packet or stream, such as parity bits, that facilitates error detection and subsequent correction.
essence —
In a digital stream or file, essence is the portion of the data that contains the “raw” or basic information of interest, excluding metadata and framing.
Exabyte —
Exabyte is a company and a family of tape–based storage products manufactured by that company.
executable —
A binary (only machine–readable) file containing a program which can be “run” or executed by a computer.
fabric —
A fabric is a collection of network or channel nodes that are cross–connected in a many–to–many scheme rather than individual, isolated point–to–point or loop topologies.
FC — Fibre Channel
Fibre Channel is a networked storage standard designed to provide high availability, performance, scalable storage along with reliable QoS and unified management. Due to industry in–fighting and lack of standardization, FC is being supplanted by other, less expensive networked storage standards.
FCIP — Fibre Channel (Over) IP
FCIP is a method of encapsulating or “tunneling” FC protocols so that they can be transported over an IP–based network. FCIP allows FC–based storage networks to be extended from LAN to MAN and WAN distances.
file–level —
File–level means the ability to read and modify only an entire file, not the underlying protocols that address the storage device on which the file resides. The term “file–level” is often used to differentiate “file–level” NASs from “block–level” SANs.
filter, to filter —
Filtering refers to the processing of data to remove or ignore unwanted information.
FireWire —
A comprehensive set of scalable standards (IEEE 1394), originating at Apple, for P2P serial data connectivity of rich media which includes IPP, broad PHY support and both async and isochronous transport.
fractional —
Used by telcos to describe a lower tier or service level of bandwidth. Fractional T-1 is a lower bandwidth version of T-1 service offered at lower cost.
frame —
In IT land, a frame is synonymous with a packet.
Frame Relay —
An interface specification based on ISDN data link layer protocol.
framing —
A frame is a self–contained unit of data, complete with addressing and control information.
framing bits —
Framing bits refer to header and trailer structures that delimit the start and end of a frame of data.
FTP— File Transfer Protocol
FTP provides basic, insecure file and directory management between remote computer systems.
FUD —
An acronym meaning fear, uncertainty and doubt, is used by public relations purveyors to undermine public confidence in a competitor.
full duplex —
Full duplex describes a equal bandwidth, bidirectional communications channel. Telephones are full duplex, while two-way radios (“walkie talkies”) are (wireless) half–duplex. Both ethernet and PCI are half–duplex, with one “talker” at a time.
GigE, Gig–E — Gigabit Ethernet
Gig-E is a short hand way of saying “1000BASE-T.” See IEEE 802.nx.
hardware —
Hardware is any tangible physical computing asset.
HBA — Host Bus Adapter
An HBA is hardware that provides interface services, both at the PHY and logical layers, between some communication standard and a computer’s OS or operating system.
To be continued…
