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, Two and Three of Pedants In A Big Box was published in March and June of 2004. Note that bold words have their own definitions in this glossary…
in–band —
When an auxiliary signaling channel shares bandwidth on the same PHY as a primary channel, then that allocation of the total available bandwidth is referred to as in–band communication. In–band signaling is the opposite of out–of–band communication. In-band and out–of–band usually refers to the passage of management, control or metadata related to network resources, like SAN nodes and LAN servers.
internet —
The IP–based public network that was originally created by the Defense Department’s DARPA (Defense Advanced Research Projects Agency) for remote command and control.
IP — Internet Protocol
The Internet Protocol, which resides in Layer 3 of the 7 layer OSI Model, provide addressing and control of datagrams or IP packets, the containers or logical information units in which all data essence resides. IP is responsible for providing “best effort” delivery from a sender’s node to the receiver’s address, along with fragmentation and possibly out of order reassembly of datagrams at the destination. IP is part of the modular TCP/IP protocol that makes ethernet such a success.
IPP — Intellectual Property Protection
Intellectual property protection mechanisms are schemes for controlling the distribution and/or availability of a digital asset and are usually integrated into such as systems as watermarking and encryption.
iSCSI — Internet SCSI
An IETF standard that provides carriage of SCSI commands via IP.
ISDN — Integrated Services Digital Network
Telco standards that allow simultaneous a single twisted pair to carry voice and digital data simultaneously over the Public Switched Telephone Network. Though ISDN was intended to replace POTS, which it did in Europe and elsewhere, it never caught on in the US due to cost and of political will. ISDN is being supplanted by packet–based network standards like DSL.
Isochronous —
A transmission technique that provides synchronous data transmission over an asynchronous network. Isochronous transmission, supported in the FireWire and RTP protocols, guarantees QoS and thus is particularly useful for the delivery of audio and video over a networked connection.
IT — Information Technology
An acronym that encompasses all aspects of computer science impacting enterprises.
kb, kilobit —
A kilobit equals 1,000 bits.
kB, kilobyte —
A kilobyte equals 1,000 bytes.
KVM — keyboard, video and mouse
KVM refers to active or passive methods of providing remote control of a computer by extending the bidirectional keyboard and mouse signaling along with the video display information.
LAN — Local Area Network
A data network that spans a relatively small, localized area, such as a building or campus.
latency —
Latency is a generic computer term, analogous to propagation delay, that quantifies the delay between the transmission of a command or datum and the acknowledgment the command or reception of that datum.
layer —
See OSI Model.
LBA — Logical Block Address
A method used in modern disk drives to translate the physical location, i.e.: cylinder, head and sector, into an abstract address that can be understood by a disk controller.
LDAP — Lightweight Directory Access Protocol
The Lightweight Directory Access Protocol is a popular protocol for providing directory services. Despite the name, LDAP isn’t very “lightweight.” LDAP has been adopted by several companies including Netscape Communications and has become a de facto standard for directory services. Other LDAP compatible offerings include Novell's Novell Directory Services (NDS) and Microsoft Corporation’s Active Directory.
linear tape —
Many tape formats, whether audio or data, rely on physically fixed head assemblies while others, such as video transports, use heads that move relative to the tape in a nearly perpendicular, rotary fashion. To achieve the high frequency magnetic transitions necessary to encode wide bandwidth signals, designers have to either move the tape very quickly past the head or move the heads really quickly past the tape. The former approach spawned data formats such as DLT, LTO and VXA. The latter approach, pioneered by Ampex in their revolutionary video tape machine, employs a rotating head assembly that spins past slowly moving tape. Video tape technology has morphed in data formats including DDS and Exabyte’s family of products.
link —
A link is a dual simplex transmission path between a pair of network elements such as nodes (HCAs or TCAs) or switches. Link hardware is specified as dual simplex, which means that send and receive wires each have their own grounds and transmit data unidirectionally and independently. The more common simultaneous bi-directional method is full duplex.
lossy codec —
See Codec.
LTO — Linear Tape Open
LTO is a middle tier, linear data tape format based on an open standard originally developed jointly by Hewlett-Packard, IBM and Certance, the company Seagate spun off after their acquisition of pioneer Conner Peripherals. LTO competes against DLT and SAIT.
MAC — Media Access Control
As part of Layer Two, the second lowest layer in the OSI Model, MAC provides a node’s interface between Layer One, the PHY, and the LLC (Logical Link Control), the “upper,” more abstract sublayer of Layer Two.
MAC address —
The MAC address is the hardware address of a network device. MAC addresses, rather than IP addresses, are usually used when security is a high priority.
MAN — Metropolitan Area Network
Larger than a LAN, a data network that spans a metropolitan area.
management, to manage —
In IT circles, management means the setup, modification and maintenance of IT assets.
markup language —
A machine–readable language that abstracts the layout of a document. Markup languages separate the structure and appearance of a page from it’s content. See xML.
MDI — Media Dependent Interface
A TLA which means the standard RJ-45 connector used for ethernet over UTP. Specifically, an MDI provides the physical and electrical connection to the cabling. An MDIX or MDI crossover is a version of MDI that enables connection between like devices without an intervening hub or switch.
Media Access Control —
See MAC.
mesh network —
Mesh networks, characterized by their lack of any centralized organization, are designed to be “multihop” systems in which any member device can transmit packets through the network. Typically ad hoc in nature, nodes to a mesh network can be added or removed without effecting the overall function. Mesh networking was designed to be more resilient than traditional hierarchical network topologies.
metadata —
Literally, the data about the data, metadata is ancillary or additional information carried along with some essence that provides additional context, modification or description.
To be continued…
