Pedant In a Big Box: Part Four

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Since the March 2004 issue, “Bitstream” columnist Oliver Masciarotte has been flipping through his audio data dictionary to define today's top IT terms as they apply to the audio professional. This month, we bring you more tech talk than you can shake an Ethernet cable at. Italicized words will be, or have been, defined in the glossary, some in upcoming issues.

ISDN (Integrated Services Digital Network):
telco standard that allows 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 U.S. due to cost and 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 to deliver audio and video over a networked connection.

IT (information technology): an acronym that encompasses all aspects of computer science — impacting enterprises.

kb, kilobit: One kilobit equals 1,000 bits.

kB, kilobyte: One kilobyte equals 1,000 bytes.

KVM (keyboard, video and mouse): active or passive methods of providing remote control of a computer by extending the bi-directional keyboard and mouse signaling and 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: a generic computer term, analogous to propagation delay, that quantifies the delay between the transmission of a command, or datum, and the acknowledgment of 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 (cylinder, head or sector) into an abstract address that can be understood by a disk controller.

LDAP (Lightweight Directory Access Protocol): a popular protocol for providing directory services. Despite the name, LDAP isn't very “light weight”: 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 and 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 its revolutionary videotape machine, employs a rotating-head assembly that spins slowly past moving tape. Videotape technology has morphed in data formats including DDS and Exabyte's family of products.

Link: 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: 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): 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 its 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 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 its 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 can be added or removed to a mesh network without affecting the overall function. Mesh networking was designed to be more resilient than traditional hierarchical network topologies.

Metadata: The data about the data, metadata is ancillary or additional information carried with some essence that provides additional context, modification or description.

OMas often feels overextended, trying to wear all of the hats needed to make a small business successful. To keep things in perspective, he listens
streaming on the Web.