This is a compilation of The Bitstream columns that appeared in Mix Magazine from 2004.
…as well as other content creators, media producers, and the curious…
Pedant In A Big Box
Pedants In A Big Box
A multipart glossary of computer terms…
See IEEE 1394.
See IEEE 802.nx.
AAC — Advanced Audio Codec
AAC is a, yes, advanced version of the widely used MP3 perceptual sub–band/transform codec with additional tools to reduce the encoded data rate while simultaneously reducing encoding artifacts. Formally known as MPEG-2 AAC.
AAF — Advanced Authoring Format
An ad hoc standard promoted by a coalition of vendors, chiefly Avid and Microsoft, along with developers and end users. AAF is a wrapper file format.
Abstraction layers are virtual programming buffers or software insulators between the inner details of some individual resource and any external entity that may want to use that resource.
Known to consumers as Dolby Digital, AC-3 is Dolby Laboratories’ 3rd generation of Perceptual Subband/Transform Codec. AC-3 is one of the mandated audio formats for both DVD-Video and ATSC Digital TV.
AIT or Advanced Intelligent Tape is a proprietary, midlevel, 8 mm, helical scan data tape standard from Sony that that pioneered the feature of embedded memory in the cartridge.
AP — Access Point
In the world of software, APIs are structured abstraction layers between the gory details of an individual application, operating system or hardware item and the world outside that software or hardware. APIs are typically “faceless,” with no user interface and without any user intervention.
Executable software that provides some useful tool(s) or function(s). In ye olden days, applications were called “programs.”
ASF — Active Streaming Format
A proprietary streaming format developed by Microsoft that provides streaming media services for the Windows Media framework.
ASP — Application Service Provider
To a rich media geek, an asset is a file that represents a valuable commodity or could be useful at some time in the future. Digital video or audio files are both considered assets. To an IT geek, assets are hardware boxes that do cool things.
Asynchronous transmission refer, among other things, to techniques that do not require a common clock between communicating devices. Since streams and files are self–clocking, timing signals are derived from framing bits within the data stream.
ATM — Asynchronous Transfer Mode
A high speed, fixed packet data transport standard that interoperates with the switched circuit telephony network. Although providing valuable QoS features, ATM is being supplanted by less expensive, IP–based standards that interoperate better with LANs and MANs.
Availability, as used by IT professionals, refers to the amount of uptime. A product, system or service with three nines or better uptime is referred to as “high availability.”
Baseband means the lowest scale or simplest rate at which of messaging occurs in a communications system.
BBF — Bitstream Boggle Factor
The tendency for Bitstream reader’s eyes to roll back into their heads as the dense geek–speak causes the reader to fall into a deep sleep.
bridge, to bridge
A bridge is a device, ether hardware or software, that “bridges” or connects two networks of the same type or protocol.
A marketing term used to denote a ruggedly constructed, full featured product suitable for high availability uses. “…this equipment is carrier class, buddy!”
CIFS is the Microsoft approach to NFS, a networked file system.
CLEC — Competitive Local Exchange Carrier
CLECs are the commercial entities created to compete with the ILECs when the Baby Bells were broken up. Covad and OneEighty Networks are two examples of CLECs.
Cloud Services are computing resources that have been abstracted from any specific hardware and are available for free or fee, over private and public networks. Cloud services are generally thought of as a pay–as-you–go, utility pricing model form of commodity computing, accessible over the Web, via a browser or “faceless” API.
Cloud Services include applications and utilities such DAM and storage are delivered, really rented, remotely. Current web services usually employ SOAP messaging formed using XML. Examples of net services are Amazon’s raft of developer services and Google’s Web APIs for generating maps.
Codecs are a broad class of signal processing that first transforms a signal from the original storage method into another so as to improve the distribution in some way. After distribution, the signal or, in our case, data, is transformed back into some semblance of the original. DTV, POTS, MP3 are all household examples of codecs.
coding, coding method
Coding refers to transforming or changing the characteristics of a signal to make it more suitable for some intended application. This optimization is usually for transmission from one location to another or for storage onto some medium which is different from the original medium. Coding can improve fidelity, optimize carrier bandwidth, increase essence carriage, improve security or provide error detection and/or correction.
COFDM — Coded Orthogonal Frequency Division Multiplexing
COFDM is the modulation method chosen for our domestic DAB service, some versions of ADSL, and DTV services in Europe and Australia. COFDM is used to encoding or impose digital audio data onto an analog carrier signal.
Colocation refers to renting a designated space where a company’s servers is situating, along with other company’s in the same physical location. All machines share common HVAC and power. For physical security, each company usually has a lockable wire cage for their equipment.
DAB — Digital Audio Broadcast
DAB is the TLA for wireless digital radio services, also know as IBOC/DAB. DAB is “terrestrial” radio in that it’s local or location–based, as opposed to national digital satellite “radio.” IBOC or in–band, on–channel means that DAB shoehorns a digital stream into the existing AM and FM analog services, maintaining backward compatibility. DAB employs lossy codecs to reduce the transmitted data rate.
A catchall TLA used interchanably with MAM or Media Asset Management, that describes the process of managing digital “assets,” files whose essence is deemed valuable by an organization. DAM usually refers to audio, motion and still image files in particular.
Data is fundamentally any information of interest but, these days, the word data implies a binary (base 2 arithmetic), machine–readable representation of information. Data is plural, the singular form is “datum.”
A data center is a physical structure, usually a stand–alone building, that is designed to house a multiplicity of computers. Data centers can be private, serving a single company or, more commonly, a public “utility” serving a variety of companies.
Often conflated with bit rate, data rate refers to the actual throughput or aggregate rate over time at which the essence is being delivered.
DDS — Digital Data Storage
DDS is a proprietary, entry level performance, 8 mm data tape standard originally based on the DAT or digital audio tape format. DDS is close to the end of the product life cycle and is being supplanted by more modern formats such as VXA.
In IT Land, to deprecate means to any feature, code or method that is either no longer desirable, is out of favor or, has been superseded by an “improved” version.
On a LAN or WAN, directory services provide an abstraction layer, identifying network assets including users, resources and the various policies assigned to each. The result is that resources and users are accessible without possessing the details about a particular resource or node. Directory services also abstract network topologies and protocols.
For an IT nerd, distributed mean decentralized rather than concentrated in one node, physical location or server.
DLT is a proprietary, midlevel, linear data tape standard originally developed by Matsushita.
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, 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 <22.214.171.124>. 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, DS0 (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 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.
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.
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 is the process that follows error detection, whereby the original data is recovered after some impairment.
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.
Exabyte is a company and a family of tape–based storage products manufactured by that company.
An exabyte, with a lower case “e,” is a very large amount of storage, some 1000 petabytes.
A binary (only machine–readable) file containing a program which can be “run” or executed by a computer.
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
FCoE 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 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.
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.
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.
In IT land, a frame is synonymous with a packet.
An interface specification based on ISDN data link layer protocol.
A frame is a self–contained unit of data, complete with addressing and control information.
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.
An acronym meaning fear, uncertainty and doubt, is used by public relations purveyors to undermine public confidence in a competitor.
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.
In IT Land, 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.
Host Channel Adapter
A Host Channel Adapter is the IB component that connects a processor to other IB devices. An HCA is really a bridge and must be able to communicate with both other HCAs and TCAs.
In IT land, a head refers to the multiplicity of magnetic read/write heads in a modern hard disk drive. Disk drives have anywhere from one or more “platters” of polished rigid disks made of aluminum or glass, that are coated with ferromagnetic material. Each side of each platter has a head, but all the heads are mounted on the same positioning actuator assembly, so only one cylinder can be accessed at any time. The heads “fly,” by ground effect, at a height of less than 2 microns above the platter, which is about 1/38th the diameter of a human hair.
A header is essentially metadata that describes what is contained in the essence, packet, frame or file remainder that follows. Typically it is the part of a packet or frame that indicates the start of the data essence or payload. Also, a preamble. Headers usually contain metadata such as addressing and error detection information.
HiPPI — High–Performance Parallel Interface
As the guys at CERN say in their general Introduction to HiPPI, “It’s Not Just for Supercomputers Anymore.” Also known as GSN or Gigabyte System Network, HiPPI is one of the original high speed LAN technologies and interoperates with Ethernet, Fibre Channel and ATM. It is an ANSI standard for a full duplex, low latency, point to point interconnect providing 100 to 200 MBytes/sec over a 50 twisted pair copper PHY with a maximum length of 25 meter. A serial version uses a glass fibre PHY at the same speed and future versions will scale up to 6.4 Gbits/second. HiPPI is used in many HPC systems.
host, to host
A host can be thought of as a server though, strictly speaking, a host can be any computer connected to a network. Servers range from single chip microcontrollers to 1U rack mounted boxes on up to refrigerator–sized “Big Iron” that can simultaneously process millions of complex financial transactions per second.
Hosting is the process of providing network services to other computers, such as providing web, database or streaming services.
Hotspots refer to nodes or APs that provide 802.11a/b/g services.
As the name implied, a system designed for very high performance number crunching. Typical applications are cyptography, scientific visualization and modeling.
HRTF – Head Related Transfer Function
HRTFs are mathematical models of the sound pressure that an arbitrary sound source produces at an ear drum, either real or virtual. A monaural sound, when convolved or processed through an HRTF, can provide varying degrees of “3D” or phantom image placement, also know as pseudostereophony. Since each person’s body shape is different and each brain has adapted to that individuality, it’s very difficult to create a single HRTF that produces convincing 3D audio for a large sampling of people.
HTML, the basic markup language of the World Wide Web, is a common way to define hypertext. As a subset of SGML or Structured General Markup Language, HTML divorces the content from the presentation of that content.
To quote inventor Theodor “Ted” Nelson (Literary Machines, Mindful Press – first printed in 1982), hypertext is “…a body of written or pictorial material interconnected in such a complex way that it could not conveniently be presented or represented on paper.” Hypertext is machine–readable and also human–readable text that is linked in a non–sequential way. HTML is a common way to deliver hypertext.
InfiniBand is an ad hoc, high speed switch-fabric architecture. The benefits of the InfiniBand specification are improved performance over older standards, ease of management, lower latency, built in security and better QoS.
The Institute of Electrical and Electronics Engineers or “eye triple ee” as it’s called, is the AES of all things electronic. The IEEE is a standards–setting body responsible for, according to their site, making “engineering decisions consistent with the safety, health and welfare of the public, and to disclose promptly factors that might endanger the public or the environment.” Unlike the AES, the IEEE is very aggressive and successful in their standardization efforts, covering a broad range of technologies impacting every aspect of daily life.
The IEEE standard codifying Apple Computer’s original FireWire standard. The original 1992 standard covers FireWire 400, a 400 Mbps smart protocol over copper. The 1394b, or “Beta" standard covers FireWire 800. In the newer standard, the copper PHY layer with two twisted pairs didn’t changed, but the transmission moved to dual simplex and channel coding changed to 8B10B. Also, other PHY choices were added, including UTP, POF and glass fibre.
Ethernet or Wired LANs including 10, 100, 1000, 10GBASE-T (twisted pair), BASE-F (fibre) & BASE-C (cable)
POE or Power–Over–Ethernet defines a standard way for network nodes to be powered over MDI, including 10/100BASE-T
The Broadband Wireless Access Standard which provide secure, full duplex, fixed wireless MAN service. Also known as WiMAX, thoughput can reach 75 Mbps and does not require line–of–sight to operate. The 802.16e extension adds roaming outside of a “home” service area. Reach can extend from 1 mile at full speed to 30 miles at reduced throughput.
Mobile Broadband Wireless Access (MBWA) — mobile as in vehicular, hence wireless
The IETF bills itself as a “large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet.” In other words, the IETF is the internet’s standards setting body.
iFCP — Internet Fibre Channel Protocol
The Internet Fibre Channel Protocol allows for carrying Fibre Channel traffic over IP–based networks. iFCP encapsulates and packetizes FC data in IP packets and maps IP addresses to individual FC devices, which breaks the distance barrier imposed by a direct–attached, FC network. Unlike FCIP, iFCP provides better fault isolation. FCIP and iFCP have been supplanted by FCoE.
ILECs are the commercial telecom entities that were in business prior to the Telecommunications Act of 1996. ILECs include tiny regional providers like the Eastern Slope Rural Telephone Association in Hugo, Colorado and the original RBOCs or Regional Bell Operating Companies; Ameritech, Bell Atlantic, BellSouth, NYNEX, Pacific Bell, Southwestern Bell and US WEST.
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.
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.
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.
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.
An acronym that encompasses all aspects of computer science impacting enterprises.
A kilobit equals 1,024 or 1,000 bits, depending on who you ask!
A kilobyte equals 1,024 or 1,000 bytes, depending on who you ask so, don’t ask!
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.
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.
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.
In the IT sense, lightweight means that the thing in question requires a small amount of computing resources, usually memory and/or CPU cycles.
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.
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.
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.
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.
Malware refers to any software that is designed to compromise the command, control or security of a computer system. Malware flavors include spyware, keyloggers, rootkits and botnets.
management, to manage
In IT circles, management means the setup, modification and maintenance of IT assets.
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
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.
Literally, the data about the data, metadata is ancillary or additional information carried along with some essence that provides additional context, modification or description.
Microcontrollers are complete computers on a chip and contain, in addition to a CPU, memory and I/O. Microcontrollers are often used by embedded systems, working transparently for the user.
mLAN is a well conceived, audio production–specific protocol overlay developed by Yamaha for the FireWire 1394 standard. As a proprietary protocol with licensing fees, mLAN has not enjoyed wide industry uptake.
MP3, a Perceptual Subband/Transform Codec, is part of the groundbreaking Motion Picture Experts Group (MPEG) standard for lossy compression of audio/video data. The motion video portion of the MPEG-1 standard was itself derived from the Joint Picture Expert Group standard for lossy compression of still images.
MPEG — Motion Picture Experts Group
The Motion Picture Experts Group, an offshoot of the still image Joint Picture Experts Group (JPEG), creates and licenses standards for digital multimedia file formats and infrastructure. The MPEG is under the ISO umbrella.
MPT — Music Pictures Television
MPT refers to the three consumables, audio, video and still images, driving consumer adoption of storage and converged products.
Multicasting is an Ethernet addressing scheme that is used to either target specific packets at specific device types, sort of (MIDI) System Exclusive for IP, or for broadcasting to all nodes simultaneously. Multicasting is a one–to–many approach to data distribution.
Name resolution refers to domain name resolution, a process whereby the Domain Name System is used to map human–readable host names to their corresponding IP addresses. This is the process that’s used to map human readable web addresses, such as www.apple.com, onto its “true” address, its IP address — which is <126.96.36.199>.
NAS — Network–Attached Storage
NAS describes a standalone storage “appliance” that provides file–level access via a network connection, typically Ethernet. NAS can reduce management overhead and eliminate unreliable cabling, while increasing in-band traffic.
A network is two or more computers connected so as to pass data, metadata, management and control messages between nodes. Networks can be publicly accessible, a “public” network like the Web or, can be “private” and accessible only with the correct security permissions and credentials.
NFS is a protocol for remote disk access over a network. NFS, a de facto standard developed by Sun Microsystems, uses UDP rather than the relatively more robust TCP protocol. In some circles, NFS also stands for Nightmare File System for the alleged unreliability of early Sun networks.
NIC — Network Interface Card or Controller
A hardware interface installed in a computer that provides a physical connection to a network.
A node is a logical instance of a computer attached to a network. Nodes are usually instantiated by a NIC.
OC-nn — Optical Carrier-nn
Optical Carrier designations are used by telcos to denote SONET service tiers, OC-48 is equal to 48 times 51.84 = 2488.32 megabits per second while OC-192 is fat enough to seamlessly interoperate with IP–based 10Gig Ethernet.
An operating system is the “low level” or underlying software that provides a computer’s most basic features and capabilities. Operating systems can be linked to specific platforms, such Mac OS on PPC, or may, like BSD Unix, be available for a wide variety of CPUs.
The OSI or Open Systems Interconnect (Reference) Model is an abstract hierarchy, developed by the ISO, that provides a standardized conceptual framework for the functional components of a heterogeneous computer network. These components are a collection or “stack” of protocols arranged into 7 “layers.” Layer 1, the PHY layer, deals with the literal nuts and bolts while the top Layer 7 formalizes the “applications” that interact with the human end user.
When an auxiliary signaling channel is relegated to a separate PHY so as not to rob bandwidth the primary channel, then that separation of signal paths is referred to as out–of–band communication. Out–of–band signaling is the opposite of in–band communication and both usually refers to the passage of management, control or metadata related to network resources, like SAN nodes and LAN servers. The opposite of in–band signaling.
In IT Land, overhead refers to any service, protocol or process that requires resources in excess of those needed by default.
P2P — Peer to Peer
Peer to peer refers to a “flat” network hierarchy, whereby clients interact directly without the intervention of servers.
packet, to packetize
A packet is an autonomous unit of data encapsulated by a protocol header and/or trailer. In general, the header provides network control and routing information for directing the packet through the fabric, while the trailer contains data for ensuring packets are not delivered with corrupted contents. Packetizing refers to encapsulating data into packet form.
A stateless network transport method whereby individual packets are routed between network nodes via a combination of packet header addressing and complex routing algorithms designed to optimize throughput. All nodes on the network are ”always on,” able to send, receive and forward packets.
Parallel, the opposite of serial, refers to moving data in a side–by–side, simultaneous fashion, either physically or virtually, whereby each clock cycle moves or processes entire bytes of data.
A petabyte is one thousand, 1024 actually, terabytes. A petabyte, once thought to be an absurdly large amount of data, is now not an uncommon amount of aggregate storage in the IT departments of enterprise and large entertainment companies.
PCI — Peripheral Component Interconnect
Originally an ad hoc standard introduced by Intel, PCI has become the world’s most widely adopted local bus standard. The current PCI-X 2.0 64-bit bus standard provides a compact form factor and supports signaling speeds up to 533 million transfers per second, up to 4.3 gigabytes per second of bandwidth which is 32 times faster than the first generation.
perceptual subband/transform codec
Perceptual subband/transform codecs are codecs designed to reduce the data rate and/or size of a digital audio file. The encoder applies a psychoacoustic model to estimate whether, in any particular band of frequencies, the signal strength in that band is above or below the perceptual threshold relative to adjacent frequency bands. If the signal is above the masking threshold, a spectral coefficient or value is generated to represent the signal in that band and the coefficient becomes the stand–in or representation of the actual audio in that band. If the signal is not above the predicted masking threshold, then that band of frequencies are tossed out to reduce the final size of the essence.
When used in the IT sense as a noun, a peripheral means any additional device added to an existing computer systems to improve the functionality. Common peripherals are displays, printers, direct–attached storage and HUI products.
PEBKAC — Problem Exists Between Keyboard And Chair
A brain fart, A.K.A. operator error. Also known as “code 18,” the human who is 18" from the display.
The physical transmission pathway in a network, usually “copper” (copper wire), glass “fibre” or POF. PHY often refers to the physical “layer” or Layer 1 of the OSI model.
Platform is slightly oblique marketing–speak for the combination of software and/or hardware chosen for a product’s or service’s design. This catchall phrase is usually used in reference to a CE product, like the use of the Symbian “platform,” as opposed to Windows CE, for a converged PDA/cell phone.
PoE — Power over Ethernet
POF — Plastic Optical Fiber
In the world of fibre optics, the actual fiber strand can be manufactured from glass or plastic. Plastic fibre has poor internal reflection, as opposed to glass’s quite high efficiency in transmitting light from one end to the other. Though POF is very low cost, this high loss results in much higher susceptibility to jitter and makes it suitable only for low data rate, short haul connections. The AES Type II and 1394b standards both specify POF as a PHY media choice.
POTS — Plain Ol’ Telephone Service
PPC — PowerPC
A highly optimized RISC CPU design co–developed by IBM, Motorola and Apple Computer. Used by both IBM in their more advanced server lines and Apple in all their computer products, the POWER architecture has largely been supplanted by Intel’s 32 bit Pentium and 64 bit Itanium families for desktop applications.
A file that instructs a computer to perform certain tasks. These days, programs are usually called applications.
Pseudo–streaming describes the use of HTTP protocols and services for streaming rather than the more appropriate RTSP or UDP protocols and services.
PSTN — Public Switched Telephone Network
The public circuit–switched telephone network, paid for in large part with our tax dollars, that originally carried POTS around the world.
QoS — Quality Of Service
Network performance metrics that include data loss rate and delay, aggregate throughput and packet priority. Usually implied to mean some guarantees that certain levels of performance are met.
QT — QuickTime
An ad hoc standard created by Apple Computer which provides a scalable, cross–platform wrapper for a wide variety of media data types. QuickTime has been incorporated into the MPEG-4 standard. QuickTime is a wrapper file format.
Rich Media describes digital multimedia presentations which integrate streaming audio and video with images, text, hypertext or any other media type. SMIL is one method for delivering rich media.
RISC — Reduced Instruction Set Computer
As opposed to CISC computers, RISC architecture is only capable of a select or streamlined number of tasks, but they perform those select tasks with great alacrity. This is akin to BMW’s supercharged Mini against a normally aspirated Chevy Camaro. Intel and AMD sell more CISC CPUs while Sun and IBM make RISC CPUs.
router, to route
A router connects multiple nodes and directs packets from one node to one or more other nodes. The forwarding mechanism “looks” within each packet header for address data. A router specializes in exchanging packets between subnets. A TCP/IP router is a basic Layer 3 or Network Layer device that provides media–independent, dynamic packet forwarding.
RSTP — Real–time Streaming Protocol
An open, standards–based protocol for streaming multimedia content to an RTP client. RTSP provides better isochronous delivery than UDP.
RTP — Real-time Transport Protocol
The RTP protocol, part of the next generation IPv6 (IP version 6) spec, provides end-to-end network transport functions suitable for applications transmitting real–time data over multicast or unicast network services. Real–time or isochronous data, such as audio, video or simulation data, requires uninterrupted, time–critical transmission. RTP data packaging, which usually flows over UTP, does not address resource reservation or QoS issues.
SAIT — Super AIT
SAN — Storage Area Network
SANs are collections of initiators, such as servers or individual “workstation,” and storage devices, typically disk or tape-based, that are connected over a specialized or private LAN. The LAN can either have a copper or fibre PHY and usually employs either the iSCSI or FC protocols.
SAS defines a fundamental change to the seemingly evergreen SCSI standard that defines a shielded serial connection in place of the unshielded parallel connection of prior versions. As with SATA, another protocol that was originally a parallel approach, SAS provides higher throughput and higher reliability with reduced form factor and lower overall cost when compared to the parallel version.
SATA — Serial ATA
A serialized version of the parallel ATA protocol. See ATA.
In IT parlance, to scale means to change the size, capacity or functionality of a system. What is often implied is that the scaling can be done in a relatively easy or straightforward way, which is seldom the case.
The SCSI standard defines a parallel, scalable interface that connects a peripheral, often storage devices, directly to a server or individual “workstation.” SCSI has largely been supplanted by other protocols, such as ATA, that are less costly or ones such as Fibre Channel, that provide higher sustained throughput and availability. As one of the oldest computer protocols extant, SCSI is still keeping up with market demand by yet again updating the standard. The ratification of the Serial Attached SCSI or SAS standard adds a new member to the already sizable SCSI family.
SDDS — Sony Dynamic Digital Sound
Sony’s 12 channel, professional version of their ATRAC lossy codec used for motion picture soundtracks.
SDK — Software Developer Kit, Software Development Kit
An SDK is a collection of programming “interfaces” or abstractions, shortcuts, reusable subroutines or “libraries,” and documentation that allows a third party to create software accessories for an existing software product or family.
SDLT — Super D
SDMI — Secure Digital Music Initiative
Yet another clueless attempt by the RIAA to “protect” digital assets.
A sector is the minimum track length or logical assignment that can be used to store information on a magnetic disk or optical disc.
In Ye Olden Days, computers were big and expensive…very expensive. During that era, the “client/server” model was born, whereby all of the investment in hardware, software, infrastructure and personnel, was centralized in one, big computer, the server, while the client was a terminal. In modern computing environments, it is still often sensible to centralize some computing resources, such as backup, with servers.
SFTP— Secure File Transfer Protocol
Secure FTP provides basic, secure file and directory management between remote computer systems.
A simplex connection provides simultaneous bi-directional data transfer, where each channel continuously transmits in both directions.
SMB — Server Message Block, Small Medium Business
The Server Message Block protocol, invented by Microsoft, is used to share Windows file systems over a network. The “Small Medium Business” version of SMB is a favorite of IT vendors, considering that sales to large scale businesses is increasingly flat. See CIFS.
SMIL — Synchronized Multimedia Integration Language
The W3C defines SMIL as “The Synchronized Multimedia Integration Language enables simple authoring of interactive audiovisual presentations.”
Known in Ye Olden Days as “programs,” software is a collection of instructions that cause a computer to perform some useful function.
SONET — Synchronous Optical Network
SONET is a Layer 1 physical, high bandwidth telephony transport protocol that provides interoperability between disparate carriers’ optical infrastructure.
A stateful paradigm refers to maintaining a well defined state, as opposed to stateless or impromptu operation. Stateful operation can be applied to an application running in a memory partition on a computer or a telephone call with it’s switched circuit connection. In a phone call, a temporary circuit is built and the two or more parties are patched in. That temporary circuit or “state” is then broken down after the phone call is terminated.
Also known as connectionless, a stateless paradigm refers to moment by moment operation. Ethernet is an example of a stateless, packet–switched protocol, where there is no fixed connection between end nodes.
In the world of IT, storage refers to any device or subsystem that holds some data for future use. Storage is usually implied to be nonvolatile and can employ magnetic, physical, optical or quantum techniques to store the information.
store & forward
In a store and forward approach to data transfer, a download is initiated and the desired data is stored, then operated on, locally. This is the opposite of streaming.
STP — shielded twisted pair
In IT land, shield cable is more rare than unshielded varieties and is only used for very high speed Bs or in “hostile” environments, where high levels of RFI and EMI are present.
A stream of data refers to a realtime flow and use of data from a source, usually a web server, to a sink or destination, usually a web client or browser. This differs from the store and forward method in that a stream is not usually, or casually, saved to the local client. Streaming can be thought of as transitory data transfer, which is by design, since streaming is used by content providers to lessen a consumer’s ability to redistribute the streamed content. As with all attempts to selectively prohibit unauthorized use and reuse of digital content, modern software allows streams to be captured locally for later reuse.
switch, to switch
A switch connects multiple nodes together in a direct, virtual point–to–point method rather than a broadcast method. A switch specializes in exchanging packets within a subnet. In the TCP/IP world of Ethernet, a switch is typically a Layer 2 or Data Link Layer device that provides filtering and forwarding of packets. Layer 3 switches are also manufactured, providing routing via hardware at “wire speeds.” Switches can either be “managed,” meaning they have remote control over operating parameters or “unmanaged,” which mean all parameters are factory preset. Unmanaged switches are also known as “dumb” switches.
A switch-fabric architecture decouples I/O operations from memory by using channel–based point–to–point connections rather than the shared bus, load and store configuration of older technologies.
In IT Land, a symbol is the logical equivalent of some physical variable that encodes a datum.
The opposite of asynchronous, synchronous means either that two or more data paths require a common timing signal or that two or more signals are operating at the same symbol rate or employ identical symbol sequences.
Used to designate various tiers of leased telco services, T1 or T-1 represents a stateful connection or circuit that provide 1.544 Mbps of symmetrical bandwidth between end points. T-1, quite costly relative to newer packet–based WAN services, is also available in “fractional” increments of 128 kbps, which reduces the monthly cost in trade for less bandwidth.
A target can be thought of as a device, such as a disk array or network adapter, that receives command from another node, device, application or service.
A terabyte, though not precisely so, is commonly thought of as 1,000 Megabytes.
TCA — Target Channel Adapter
A Target Channel Adapter, is the IB component that connects an input/output device to other IB devices. TBAs only require support for capabilities appropriate to the particular input/output device. TCAs are used inside of or are attached to a device, such as a solid state memory cache, or device group, such as a tape library.
TCP, along with IP, is half of the modular TCP/IP protocol that has made ethernet such a success. TCP is responsible for packetizing or breaking up messages in order to send them over an uncertain pathway (the Internet) and reassembling the packets at the intended destination.
TDM — Time Domain Multiplex(ing)
A technique widely used since the 1960s, especially in the circuit–swtched telephony, to multiplex or interweave multiple data streams onto a single carrier channel by quickly chopping up each stream and sequentially assembling them into a composite data stream.
A telco is a telephone company, typically an ILEC.
Telecom, short for telecommunications, is the industry that was created with and has wrapped around the invention of the telephone.
Telephony refers to all things having to do with telephones and telephone services.
Terminals, also known as dumb terminals, have been reborn under the new rubric of “thin client.” Whether terminal or thin client, these low cost network nodes are basically a NIC, display and keyboard with little or no local processing capabilities. Thin clients are quite popular in corporate environments because they aren’t susceptible to viruses and other malware.
“3 nines” is another way of saying 99.9, and usually refers to percentage as in, 99.9%. “Four nines,” 99.99% and “five nines” or 99.999% are also common and related terms. All are used to typically denote up–time or availability, with higher percentages representing better average reliability.
See data rate.
TLAs are the linguistic currency of modern business and, more specifically, modern geekdom.
TLDs were devised to bring order to the then–new internet. The eight original TLDs included .com, .net, .org for commercial, network services and non–profits, respectively. In addition, there were .edu for educational institutions, with .int and .mil reserved for our military. Later, as the web spread across the globe, countries other than the US were assigned TLDs; .tv is for the tiny island of Tuvalu, .ca for Canada, .uk for the United Kingdom, .jp for Japan, .de for Germany, .fm for Micronesia, .no for Norway, et cetera. Recently, new TLD have been added, included .biz, .me, .mobi, .pro and .name. TLDs are assigned and controlled by ICANN.org, the Internet Corporation For Assigned Names and Numbers.
A description of the process of developing an DAM “solution” based on an understanding of the content’s context and end user’s needs. A top down approach, as opposed to the bottom up method, is the information sciences way of solving the problem.
As it relates to networks, topography refers to the physical layout or logical structure of a network.
In a hard disk drive, a track is the magnetic trace or path of an individual read/write head while the actuator arm on which it is mounted is stationary.
The opposite of a header, a trailers denote the end of the symbol sequence that a header “starts.”
Triple DES refers to a triple encryption of information using the DES algorithm. Since DES encryption is fairly easy to break, three successive encodings are enough to make it reasonable secure. Triple DES has largely been replaced by AES encryption.
UPD is a collection of stateless, connectionless (setup–free) network, transport and session (OSI Layer 3) protocols used to implement, among other things, NFS. UDP, like TCP, is layered on top of IP though, unlike TCP, doesn’t even try to guarantee delivery.
First developed by Bell Labs Unix is a powerful, flexible, interactive operating system. Unix was the first OS written in C, a high level language now widely used by programmers everywhere. Since it was first released in 1969, Unix has grown and evolved, often with the addition of free contributions of academic programmers. Solaris, AIX, HP-UX, Mac OS and IRIX are all Unix “distributions” or versions, while the increasingly popular Linux is modeled after Unix. UNIX™ is a trademarked Unix distribution owned by The Open Group.
Uptime, the opposite of downtime, refers to the amount or percentage of time that a product, system or service is operational.
A URL is a human–readable way of indirectly referring to a network node’s IP address and associated directory and file structure. The URL <http://www.seneschal.net/index.html> “tells” a web browser to use the HTTP protocol to open the file “index.html” at the IP address mapped to the domain “seneschal.net.” Index.html is the default file name that browsers “look for” when going to a bare domain name like <seneschal.net>. So, the index.html is implied if you only enter <www.seneschal.net> into your browser’s address field.
USB — Universal Serial Bus
A standard for host–based, wired or wireless serial data connectivity of computer peripherals over asynchronous transport. USB was developed by Intel to replace the RS-232 serial protocol and PHY.
UTP was first popularized by telcos for use as premises wiring. Once it became ubiquitous, UTP was pressed into service to replace the more costly and unwieldy coaxial cable that was first specified for Ethernet.
Virtualization refers to the increasingly valuable process or packaging of abstracting the specifics of a networked environment, typically networked storage or an entire “computer,” in order to better administer and utilize what are usually piecemeal “islands” of network assets. Virtualization is typically performed by proprietary software packages, though vendor–agnostic products are available. Virtualization is also available as embedded features of some vendor’s SAN “intelligence” or functionality.
A virus is self–replicating, self–executing code designed to install itself on as many hosts as possible. Viruses are usually malware, written specifically to either do harm to the host or to serve some other malicious purpose.
VoIP — Voice over IP
Voice over IP, pronounced “voyp,” is the process of passing digtized voice traffic over the internet as an alternative to traditional telco voice services. VoIP includes VoWLAN or Voice over a WLAN which includes VoWiFi or Voice over a WiF network. Both Vonage and Google Voice are examples of VoIP services.
VPN — Virtual Private Network
VPNs are encrypted connections over public networks, be they LANs, MANs or WANs, that use the internet to securely and inexpensively span long distances. To build or hire a private network for the same job would cost a great deal more than using a VPN.
VXA is a proprietary, entry level, linear data tape standard originally developed by Ecrix. VXA became part of the Exabyte family of products and has been retired.
W3C — the World Wide Web Consortium
The W3C is the World Wide Web’s standards setting body.
The web browser, first created as Mosaic by Sir Tim Berners-Lee, is the principal application used to interact with the Worldwide Web. Firefox, Opera and Safari are all examples of browsers while Internet Explorer, the most widely used example, is increasingly being supplanted by the above mentioned alternatives.
See Cloud Services.
WiFi or Wireless Fidelity (go figure) refers to wireless networking using 802.11b protocols. Public Wi-Fi APs and services have become so well accepted that it’s not uncommon to find McWi-Fi on the menu at urban McDonalds.
An ad hoc standard created by Microsoft which provides a scalable, cross–platform framework for a wide variety of media data types.
As the name implies, wireless means information transfer by means other than wires; radio, microwave, light (typically infrared) and smoke signals all are wireless forms of communication.
The opposite of wireless, wireline means to employ wires in a communications system.
Wire speed is a code word for hardware–based, as opposed to software–based.
WMA — Windows Media Audio
WMA is Microsoft’s family of codecs for packetized audio data. There are four members of the Windows Media audio family, a general codec, a “Professional” version support 24 bit word lengths and multiple channels, a “Lossless” version and a “Voice” version optimized primarily for reproducing speech.
A vague term that has come to describe a desktop computer of more than average capabilities. A “professional” version of a personal computer.
Invented by Sir Tim Berners–Lee, the “Web” is a combination of ad hoc and proprietary technologies, applications and standards that provide multilingual, interoperable electronic delivery of text, hypertext and audiovisual content. The Web is based on two key systems, the interconnected public and private network know as the Internet and the web browser.
A wrapper refers to a file format that encapsulates a variety of metadata and essence into one package.
WWW — world wide web
See Worldwide Web.
xBASEy refers to the nomenclature for designating IEEE 802.3 or ethernet cabling. The x is the design data rate, 10 through 40,000 Mbps while the y refers to the cabling type or category. Categories include the original thick coaxial cable (BASE-5), the second generation thin coax or “Thinnet” (BASE-2), the original voice grade UTP (BASE-VG), the more common improved UTP (BASE-T) and BASE-F for glass fibre, the PHY capable of supporting the highest data rates of all cabling types.
Xerox PARC — Xerox Palo Alto Research Center
Founded in 1970, PARC is Xerox’s attempt to drive competitiveness through innovation. An example of pure research yielding some impressive results, researchers at Xerox’s PARC were responsible for changing the face of modern personal computing, inventing, among other things, the graphical user interface, the computer mouse, “the Ethernet” and the laser printer. Despite their valuable contributions, Xerox neverseems to have been able to capitalize on its PARC investments.
SGML, the parent of all subsequent xML dialects, is a standardized language for describing or “marking up” the appearance of a document. SGML and it’s dialects separate the content from the appearance of a document. More recent standards include HTML, the Hypertext Markup Language used for web pages, VRML, the Virtual Reality Markup Language used for “VR” delivery, SAML, the Security Assertion Markup Language used for identification and authenication, and XML, the Extensible Markup Language, which is used for net services.