In March 2004, Mix introduced its IT glossary for pro audio folks. The data dictionary continues this month. Italicized words were defined in past glossaries, some in upcoming installments.
HCA (Host Channel Adapter): 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.
Head: the multiplicity of 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, coated with ferromagnetic material. Each side of each platter has a head, but all of 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.
Header: 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, “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/second over a 50 twisted-pair copper PHY with a maximum length of 25 meters. A serial version uses a glass-fiber PHY at the same speed; future versions will scale up to 6.4 Gbits/second.
Host, to 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 rackmounted boxes on up to a refrigerator-sized “big iron” that can simultaneously process millions of complex financial transactions per second.
Hosting: the process of providing network services to other computers, such as providing Web, database or streaming services.
Hotspot:nodes or APs that provide 802.11 a/b/g services.
HRTF (Head-Related Transfer Function): mathematical models of the sound pressure that an arbitrary sound source produces upon an eardrum, either real or virtual. A monaural sound, when convolved or processed through an HRTF, can provide varying degrees of 3-D or phantom-image placement — also known as pseudostereophony. Because each person's body shape is different and each brain has adapted to that individuality, it's extremely difficult to create a single HRTF that produces convincing 3-D audio for a large sampling of people.
HTML: The basic markup language of the World Wide Web, HTML is a common way to deliver hypertext.
Hypertext: To quote inventor Ted Nelson's Literary Machines (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- and human-readable text that is linked in a nonsequential way. HTML is a common way to deliver hypertext.
IB (InfiniBand): 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.
IEEE: The Institute of Electrical and Electronics Engineers, or “eye triple-ee” as it's called, is the AES of all things electronic. According to its Website, the IEEE is a standards-setting body responsible for 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.” The IEEE is very aggressive in its standardization efforts, covering a broad range of technologies impacting every aspect of daily life.
IEEE 1394: the IEEE standard codifying Apple Computer's original FireWire standard. The original 1992 standard covers FireWire 400, a 400Mbps 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 change, but the transmission moved to dual simplex and channel coding changed to 8B10B. Also, other PHY choices were added, including UTP, POF and glass fiber.
IEEE 802.nx: the 802 working group of the IEEE sets the standards for data networking. There are many individual committees addressing specific applications. These include:
802.1:layer 2 wired LAN standards including ad (link aggregation), Q (support for VLANs, or virtual LANs) and p (packet prioritization).
802.3:Ethernet or wired LANs including 10, 100, 1,000, 10GBase-T (twisted-pair), Base-F (fiber) and Base-C (cable).
802.3af: POE (Power Over Ethernet) defines a standard way for network nodes to be powered over MDI, including 10/100Base-T.
802.11: wireless LAN standards including a (54 Mbps [18-22 Mbps throughput]), b (11 Mbps [6 Mbps throughput]), d (internationalization), e (enhanced Media Access Control layer for QoS) and g (harmonizes a and b).
802.15: low-power wireless PANs such as low-complexity Bluetooth, UWB-based high-rate PANs and mesh networks.
802.16: the Broadband Wireless Access Standard that provides secure, full-duplex, fixed wireless MAN service. Also known as WiMAX, throughput 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 one mile at full speed to 30 miles at reduced throughput.
802.20: Mobile Broadband Wireless Access (MBWA); mobile, as in vehicular.
IETF (Internet Engineering Task Force): 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, it's the Internet's standards-setting body.
IFCP (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. IFCP provides fault isolation.
ILEC (Incumbent Local Exchange Carrier): a commercial telecom entity that was in business prior to the Telecommunications Act of 1996. ILECs include tiny regional providers such as the Eastern Slope Rural Telephone Association in Hugo, Colo., and the original RBOCs (Regional Bell Operating Companies): Ameritech, Bell Atlantic, BellSouth, NYNEX, Pacific Bell, Southwestern Bell and US WEST.
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 refer to the passage of management, control or metadata related to network resources such as SAN nodes and LAN servers.
Internet: the IP-based public network that was created by the Defense Department's DARPA (Defense Advanced Research Projects Agency) for remote command and control.
IP (Internet Protocol): Residing in Layer 3 of the seven-layer OSI model, IP provides addressing and control of datagrams or IP packets, the containers or logical information units that 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 re-assembly of datagrams at the destination. IP is part of the modular TCP/IP protocol that makes Ethernet such a success.
IPP (Intellectual Property Protection): schemes to control the distribution and/or availability of a digital asset; usually integrated into such systems as watermarking and encryption.
ISCSI (Internet SCSI): an IETF standard providing carriage of SCSI commands via IP.
If you have a TLA or fragment of geek speak that you can't decode, then stop bywww.seneschal.netand drop me some mail.