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ASIC (Application Specific Integrated Circuit)

A chip that is custom designed for a specific application rather than a general-purpose chip such as a microprocessor. The use of ASICs improve performance over general-purpose CPUs, because ASICs are "hardwired" to do a specific job and do not incur the overhead of fetching and interpreting stored instructions. An ASIC chip performs an electronic operation as fast as it is possible to do so, providing, of course, that the circuit design is efficiently architected.

ASSP (Application Specific Standard Part/Product)

Another term for an ASIC chip.

CSIC (Customer Specific Integrated Circuit)

Pronounced "C-sick." Another term for ASIC, which was coined by Motorola. Some feel this is a more accurate description of an ASIC chip, since ASICs can be used for a variety of purposes. CSIC is somewhat a redundant reference to an ASIC chip. ASICs are already customized for a specific use.

gate array

An unfinished chip with electronic components that have not been connected. The chip is completed by designing and adhering the top metal layers which provide the interconnecting pathways. This final masking stage is less costly than designing the chip from scratch. The gate array is made up of basic cells, each cell containing some number of transistors and resistors depending on the vendor. Using a cell library (gates, registers, etc.) and a macro library (more complex functions), the customer designs the chip, and the vendor's software generates the masks that connect the transistors.

hard macro

The design of a logic function that specifies how the required logic elements are interconnected and specifies the physical pathways and wiring patterns between the components. Also called a "macro cell."

soft macro

The design of a logic function that specifies how the required logic elements are interconnected, but not the physical wiring pattern on the chip. Contrast with hard macro.

NVM (non-volatile memory)

Memory that holds its content without power. ROMs, PROMs, EPROMs and flash memory are examples. Disks and tapes may be called non-volatile memory, but they are usually considered storage devices. Sometimes the term refers to memory that is inherently volatile, but maintains its content because it is connected to a battery at all times.

ROM (Read Only Memory)

A memory chip that permanently stores instructions and data. Its contents are created at the time of manufacture and cannot be altered. ROM chips are used to store control routines in personal computers (ROM BIOS), peripheral controllers and other electronic equipment. They are also often the sole contents inside a cartridge that plugs into printers, video games and other systems. When computers are used in hand-held instruments, appliances, automobiles and any other such devices, the instructions for their routines are generally stored in ROM chips or some other non-volatile chip such as a PROM or EPROM. Instructions may also be stored in a ROM section within a general-purpose computer on a chip.

PROM (Programmable Read Only Memory)

A permanent memory chip that is programmed, or filled, by the customer rather than by the chip manufacturer. It differs from a ROM, which is programmed at the time of manufacture. PROMs have been mostly superseded by EPROMs, which can be reprogrammed.

EPROM (Erasable Programmable ROM)

A programmable and reusable chip that holds its content until erased under ultraviolet light. EPROMS have a lifespan of a few hundred write cycles. EPROMS are expected to eventually give way to flash memory.

EEPROM (Electrically Erasable Programmable Read Only Memory)

A memory chip that holds its content without power. It can be erased, either within the computer or externally and usually requires more voltage for erasure than the common +5 volts used in logic circuits. It functions like non-volatile RAM, but writing to EEPROM is slower than writing to RAM. EEPROMs are used in devices that must keep data up-to-date without power. For example, a price list could be maintained in EEPROM chips in a point of sale terminal that is turned off at night. When prices change, the EEPROMs can be updated from a central computer during the day. EEPROMs have a lifespan of between 10K and 100K write cycles.

flash memory

A memory chip that holds its content without power. Derived from the EEPROM chip technology, which can be erased in place, flash memory is less expensive and more dense. Unlike DRAM and SRAM memory chips, in which a single byte can be written, flash memory must be erased and written in fixed blocks, typically ranging from 512 bytes up to 256KB. The term was coined by Toshiba for its ability to be erased "in a flash." Flash chips have been used in various communications and industrial products as well as to replace ROM BIOS chips so that the BIOS could be updated. Flash chips generally have lifespans from 100K to 300K write cycles. Flash memory chips are conveniently packaged as "flash cards," using the PC Card, CompactFlash, Smart Media and similar formats. They have become widely used as film in digital cameras as well as auxiliary storage in a variety of handheld commercial and consumer devices. There are two types of flash interfaces. The earlier linear flash, which is also used to execute a program directly from the chip (XIP), requires Flash Translation Layer (FTL) or Flash File System (FFS) software to make it look like a disk drive. There are various implementations of FTL and FFS. The second type is the ATA interface, which is widely used for hard disks and has the same 512-byte block (sector) size.

Smart Media

An ultra-compact flash memory format developed by Toshiba. About the size of CompactFlash, but as thin as a credit card, Smart Media cards are popular storage for digital cameras. Available in 3.3 and 5 volt variations, Smart Media cards require no assembly in manufacture as they are actually flash memory chips in a unique chip package. The cards can be plugged into a Smart Media socket or into a standard Type II PC Card slot with an adapter. Capacities up to 64MB are expected by late 1999.

Memory Stick

A flash memory card from Sony designed for handheld digital appliances such as cameras and camcorders. Introduced in 1998 with 4 and 8MB capacities, the tiny modules are less than 1x2" and about a tenth of an inch thick (.85 x 1.97 x .11"). Transfer to a PC is made via a PC Card adapter.

PROM programmer

A device that writes instructions and data into PROM chips. The bits in a new PROM are all 1s (continuous lines). The PROM programmer only creates 0s, by "blowing" the middle out of the 1s. Some earlier units were capable of programming both PROMs and EPROMs.

FPGA (Field Programmable Gate Array)

A programmable logic chip (PLD) with a high density of gates. There are a variety of FPGA architectures, some of which can be very sophisticated, including not only programmable logic blocks, but programmable interconnects and switches between the blocks.

PLD (Programmable Logic Device)

A logic chip that is programmed at the customer's site. It uses either fusible links, which are "blown" to open the lines or Actel's Antifuse technology to fuse them together. There are a wide variety of PLD techniques; however, most PLDs are of the PLA (Programmable Logic Array) or PAL (Programmable Array Logic) variety, which provide different configurations of AND and OR gates. Unlike gate arrays, which require the final masking fabrication process, PLDs are easily programmable in the field. PLDs are always used for logical functions, but programmable storage chips such as PROMs and EPROMs may also be considered as PLDs if they contain program code rather than just data.

SPLD (Simple PLD)

A programmable logic device that provides an array of logic blocks that can be programmed.

CPLD (Complex PLD)

A programmable logic device that includes a programmable interconnect between the logic blocks.

Antifuse

A PLD technology from Actel Corporation, that works the opposite of typical programmable chip methods. Instead of creating open circuits (blowing the fuse), closed circuits are created. Two metal layers sandwich a layer of non-conductive, amorphous silicon. When voltage is applied to this middle layer, the amorphous silicon is turned into polysilicon, which is conductive.

EDA (Electronic Design Automation)

Using the computer to design and simulate the performance of electronic circuits on a chip.

VHDL (VHSIC Hardware Description Language)

A hardware description language (HDL) used to design electronic systems at the component, board and system level. VHDL allows models to be developed at a very high level of abstraction. Initially conceived as a documentation language only, most of the language can today be used for simulation and logic synthesis. VHDL is an IEEE standard, but was initially developed for the U.S. military's VHSIC program.

Verilog

A hardware description language (HDL) used to design electronic systems at the component, board and system level. Developed by Phil Morby, it was initially developed as a simulation language that could also be used to describe the stimulus (test factors). By the late 1980s, Verilog was the de facto standard for proprietary HDLs. After Cadence put it into the public domain, it became an IEEE standard. A Verilog simulator is a separate entity, but the term by itself typically refers to the language (HDL).

VHSIC (Very High Speed Integrated Circuit)

Pronounced "vizik." Ultra-high-speed chips employing LSI and VLSI technologies.

logic synthesis

The conversion of a high-level electronic circuit description into a list of logic gates and their interconnections, called the netlist. Every logic synthesis program understands some subset of Verilog and VHDL. The market leader in logic synthesis software is Synopsis.

silicon compiler

Software that translates the electronic design of a chip into the layout of the logic gates, including the actual masking from one transistor to another. The source of the compilation is either a high-level description or the netlist.

netlist

A list of logic gate and their interconnections which make up a circuit.

back end

The support components of a computer system. It typically refers to the database management system (DBMS), which is the storehouse for the data.

front end

The head, starting point or input side in a system. For example, it may refer to the graphical interface on a user's workstation where all data is entered or to a communications system, such as a front end processor or TP monitor that accepts incoming transactions and messages.

MCM (MultiChip Module or MicroChip Module)

A chip housing that uses a ceramic base and contains two or more raw chips closely connected with high-density lines. This packaging method saves space and speeds processing due to short leads between chips. MCMs were originally called microcircuits or hybrid microcircuits, since this technique was suited for mixing analog and digital components together. MCMs offer a more workable solution to wafer scale integration, in essence, building the "superchip," which has been very difficult to implement.

hybrid microcircuit

An electronic circuit composed of different types of integrated circuits and discrete components, mounted on a ceramic base. Used in military and communications applications, it is especially suited for building custom analog circuits including A/D and D/A converters, amplifiers and modulators.

embedded system

An embedded system implies a fixed set of functions programmed into a non-volatile memory (ROM, flash memory, etc.) in contrast to a general-purpose computing machine.

realtime system

A computer system that responds to input signals fast enough to keep an operation moving at its required speed.

RTOS (RealTime Operating System)

An operating system designed for use in a realtime computer system.

SONET (Synchronous Optical NETwork)

A fiber-optic transmission system for high-speed digital traffic. Employed by telephone companies and common carriers, SONET speeds range from 51 megabits to multiple gigabits per second. SONET is an intelligent system that provides advanced network management and a standard optical interface. It uses a self-healing ring architecture that is able to reroute traffic if a line goes down. SONET backbones are widely used to aggregate lower-speed T1 and T3 lines. SONET is specified in the Broadband ISDN (BISDN) standard. The European counterpart is SDH. Following are the levels of service. OC (Optical Carrier) refers to the optical signal, and STS (Synchronous Transport Signal) refers to the electrical signal, which is the same speed.
 
SONET Circuits Service Speed (Mbps) Implementation
OC-1, STS-1 51.84 28 DS1s or 1 DS3
OC-3, STS-3 155.52 3 STS-1s
OC-3c, STS-3c 155.52 Concatenated
OC-12, STS-12 622.08 12 STS-1, 4 STS-3
OC-12c, STS-12c 622.08 12 STS-1, 4 STS-3c
OC-48, STS-48 2488.32 48 STS-1, 16 STS-3
OC-192, STS-192 9953.28 192 STS-1, 64 STS-3
OC-768, STS-768 38813.12 768 STS-1, 256 STS-3

SDH (Synchronous Digital Hierarchy)

The European counterpart to SONET.

ISDN (Integrated Services Digital Network)

An international telecommunications standard for transmitting voice, video and data over digital lines running at 64 Kbps. The telephone companies commonly use a 64 Kbps channel for digitized, two-way voice conversations. ISDN service is available in most parts of the U.S. ISDN uses 64 Kbps circuit-switched channels, called B channels, or "bearer" channels, to carry voice and data. It uses a separate D channel, or "delta," channel for control signals. The D channel is used to signal the telephone company computer to make calls, put them on hold and activate features such as conference calling and call forwarding. It also receives information about incoming calls, such as the identity of the caller. ISDN's basic service is Basic Rate Interface (BRI), which is made up of two 64 Kbps B channels and one 16 Kbps D channel (2B+D). If both channels are combined into one, called bonding, the total data rate becomes 128 Kbps and is four and a half times the bandwidth of a V.34 modem (28.8 Kbps). ISDN's high-speed service is Primary Rate Interface (PRI). It provides 23 B channels and one 64 Kbps D channel (23B+D), which is equivalent to the 24 channels of a T1 line. When several channels are bonded together, high data rates can be achieved. For example, it is common to bond six channels for quality videoconferencing at 384 Kbps. In Europe, PRI includes 30 B channels and one D channel, equivalent to an E1 line.

BISDN (Broadband ISDN)

A second-generation ISDN standard that uses fiber-optic cables for speeds of 155 Mbps and higher. BISDN's bottom three layers of implementation comprise ATM (asynchronous transfer mode), which by itself is gaining ground as a networking technology for LANs and WANs.

CO (central office)

A local telephone company switching facility that covers a geographic area such as a small town or a part of a city. It is where subscribers' telephone lines in the local loop are connected to intracity and intercity trunks. There are more than 25,000 central offices in the U.S.

PSTN (Public Switched Telephone Network)

The worldwide voice telephone network. Once only an analog system, the heart of most telephone networks today is all digital. In the U.S., most of the remaining analog lines are the ones from your house or office to the telephone company's central office (CO).

AMPS (Advanced Mobile Phone Service)

The analog cellular mobile phone system in North and South America and more than 35 other countries. It uses the FDMA transmission technology. AMPS is the cellular equivalent of POTS.

POTS (Plain Old Telephone Service)

 

VPN (Virtual Private Network)

A private network that is configured within a public network. For years, common carriers have built VPNs that appear as private national or international networks to the customer, but physically share backbone trunks with other customers. VPNs have been built over X.25, Switched 56, frame relay and ATM technologies. Today, there is tremendous interest in building VPNs over the Internet. In order to maintain privacy in a public environment, VPNs use access control and encryption.

broadband

(1) High-speed transmission. The term is commonly used to refer to communications lines or services at T1 rates (1.544 Mbps) and above. (2) A technique for transmitting data, voice and video using the same frequency division multiplexing (FDM) technique as cable TV. Modems are required for this method, because the digital data has to be modulated onto the line.

baseband

A communications technique in which digital signals are placed onto the transmission line without change in modulation. It is usually limited to a few miles and does not require the complex modems used in broadband transmission. Common baseband LAN techniques are token passing ring (Token Ring) and CSMA/CD (Ethernet). In baseband, the full bandwidth of the channel is used, and simultaneous transmission of multiple sets of data is accomplished by interleaving pulses using TDM (time division multiplexing). Contrast with broadband transmission, which transmits data, voice and video simultaneously by modulating each signal onto a different frequency, using FDM (frequency division multiplexing).

narrowband

In communications, transmission rates from 50 bps to 64 Kbps. Earlier uses of the term referred to 2,400 bps or less or to sub-voice grade transmission from 50 to 150 bps. Contrast with wideband and broadband.

wideband

In communications, transmission rates from 64 Kbps to 2 Mbps.

SIMD (Single Instruction stream Multiple Data stream)

A computer architecture that performs one operation on multiple sets of data, for example, an array processor. One computer or processor is used for the control logic and the remaining processors are used as slaves, each executing the same instruction. Contrast with MIMD.

MIMD (Multiple Instruction stream Multiple Data stream)

A computer architecture that uses multiple processors, each processing its own set of instructions simultaneously and independently of the others. Contrast with SIMD.

VLIW (Very Long Instruction Word)

A CPU architecture that reads a group of instructions and executes them at the same time. For example, the group (word) might contain four instructions, and the compiler ensures that those four instructions are not dependent on each other so they can be executed simultaneously. Otherwise, it places no-ops (blank instructions) in the word where necessary.

prediction

A VLIW concept. In CPU instruction execution, predicting the outcome of a branch so that those instructions may be executed in parallel with the current instructions. If the CPU guesses the wrong branch, it will take extra machine cycles to go back and execute the correct one; however, on average, if the prediction algorithms are good, overall performance is increased.

EPIC (Explicitly Parallel Instruction Computing)

The parallel architecture used in Intel's IA-64 chips. It was originally developed by HP.

IA-64 (Intel Architecture-64)

The 64-bit architecture used in Intel's upcoming Merced chip. Instead of the variable-length instructions of the x86, which are from one to 14 bytes in length, IA-64 uses four-byte, fixed-length instructions bundled in sets of three (long instruction words). IA-64 chips use 256 registers for integer and floating point operations compared to 16 in the x86. It also employs a technique called predication, where both sides of a branch instruction are executed in parallel. When the correct branch is determined, the results for the incorrect side are discarded. With IA-64, compilers have to be much more intelligent, placing codes into the instruction bundles that tell the CPU how to execute instructions in parallel. They also have to place instructions in interleaved order for predication. If predication is not set up, the CPU will perform traditional branch prediction, whereby it attempts to guess the outcome of a branch and executes those instructions in parallel. IA-64 also supports speculative loading, which loads data into its registers before the instructions actually need to process it. Explicitly Parallel Instruction Computing (EPIC) is Intel's brand name for its new parallel architecture.

Merced

Intel's next-generation CPU architecture, also known as the P7. Expected in 2000, it is jointly designed by Intel and HP. Although it uses a new 64-bit instruction architecture (IA-64), Merced is also expected to run x86 and PA-RISC software natively with clock speeds at 600MHz and beyond. In order to take full advantage of the 64-bit architecture, applications have to be upgraded. Merced chips should contain more than 10 million transistors using .18 micron technology, and its IA-64 architecture is designed for fast parallel instruction execution. The bottom line is that Merced was designed at the end of the 20th century, whereas x86 chips hark back to an architecture from the early 1970s, which was based on a fraction of the number of transistors available today. The Merced should be a formidable product. In addition, not only will HP-UX and Windows NT run on Merced, but Digital Unix, SCO UnixWare and Solaris are expected to be ported to the new chip family.

superscalar

A CPU architecture that allows more than one instruction to be executed in one clock cycle.

DSP (Digital Signal Processor)

A special-purpose CPU used for digital signal processing. It provides ultra-fast instruction sequences, such as shift and add, and multiply and add, which are commonly used in math-intensive signal processing applications. DSP chips are widely used in myriads of devices, including sound cards, fax machines, modems, cellular phones, high-capacity hard disks and digital TVs (see definition 2 below). The first DSP chip used in a commercial product was believed to be from TI, which was used in its very popular Speak & Spell game in the late 1970s.

firmware

A category of memory chips that hold their content without electrical power and include ROM, PROM, EPROM and EEPROM technologies. Firmware becomes "hard software" when holding program code.

yacc (Yet Another Compiler Compiler)

A UNIX compiler that is used to create C compilers. Part of its code is included in the generated compiler.

bison

The Free Software Foundation's version of yacc.

DSLAM (DSL Access Multiplexor)

A central office (CO) device for ADSL service that intermixes voice traffic and DSL traffic onto a customer's DSL line. It also separates incoming phone and data signals and directs them onto the appropriate carrier's network.

DS (Digital Signal)

A classification of digital circuits. The DS technically refers to the rate and format of the signal, while the T designation refers to the equipment providing the signals. In practice, "DS" and "T" are used synonymously; for example, DS1 and T1.
NORTH AMERICA, JAPAN, KOREA, ETC.
Voice Service Channels Speed
DS0 1 64 Kbps
DS1 24 1.544 Mbps (T1)
DS1C 48 3.152 Mbps (T1C)
DS2 96 6.312 Mbps (T2)
DS3 672 44.736 Mbps (T3)
DS4 4032 274.176 Mbps (T4)
EUROPE (ITU)
Voice Service Channels Speed (Mbps)
E1 30 2.048
E2 120 8.448
E3 480 34.368
E4 1920 139.264
E5 7680 565.148

set-top box

The cable TV box that "sits on top" of the TV set. A variety of new set-top boxes are emerging for Internet TV and other interactive services.

MMU (Memory Management Unit)

A virtual memory circuit that translates logical addresses into physical addresses.

NIS (Network Information Services)

A naming service from SunSoft that allows resources to be easily added, deleted or relocated. Formerly called Yellow Pages, NIS is a de facto UNIX standard. NIS+ is a redesigned NIS for Solaris 2.0 products. The combination of TCP/IP, NFS and NIS comprise the primary networking components of UNIX.

NFS (Network File System)

The UNIX networking protocol that allows files and printers to be shared across the network. This de facto UNIX standard, which is widely known as a distributed file system, was developed by Sun. NFS services are also available on Windows NT servers, which enables UNIX workstations to gain access to its files and printers. The counterpart of NFS in the DOS, Windows and OS/2 world is SMB (Server Message Block), and in NetWare, NCP (NetWare Core Protocol). NFS, SMB and NCP are all high-level protocols (layers 5 to 7) that provide open and close file and read and write functions as well as access control. They ride on top of the transport protocols (TCP/IP, NetBEUI, IPX/SPX), which manage the transfer. See WebNFS, SMB and NCP.

DSU/CSU (Digital Service Unit/Channel Service Unit)

A pair of communications devices that connect an inhouse line to an external digital circuit (T1, DDS, etc.). It is similar to a modem, but connects a digital circuit rather than an analog one. The CSU terminates the external line at the customer's premises. It also provides diagnostics and allows for remote testing. If the customer's communications devices are T1 ready and have the proper interface, then the CSU is not required, only the DSU. The DSU does the actual transmission and receiving of the signal and provides buffering and flow control. The DSU and CSU are often in the same unit. The DSU may also be built into the multiplexor, commonly used to combine digital signals for high-speed lines.

Switched 56

A dial-up digital service provided by local and long distance telephone companies. There is a monthly fee and per-minute charge like the analog voice network. For connection, a DSU/CSU is used instead of a modem. Switched 56 uses a 64 Kbps channel, but one bit per byte is used for in band signaling, leaving 56 Kbps for data.

X.25

An ITU standard (1976) for packet switching networks. Public X.25 communications networks have been available worldwide for many years, which provide a switched data service at 56 Kbps or less. Such networks are widely used for point of sale (POS) terminals, credit card verifications and automatic teller machine transactions. New packet-switched networks employ frame relay and SMDS technologies rather than X.25.

frame relay

A high-speed packet switching protocol used in wide area networks (WANs). It has become popular for LAN to LAN connections across remote distances, and services are provided by all the major carriers. Frame relay is faster than traditional X.25 networks, because it was designed for today's reliable circuits and performs less rigorous error detection. Frame relay provides for a granular service up to DS3 rates of 44.736 Mbps and is suited for data and image transfer. Because of its variable-length packet architecture, it is not the most efficient technology for realtime voice and video.

SMDS (Switched Multimegabit Data Service)

A high-speed, switched data communications service offered by the local telephone companies for interconnecting LANs in different locations. It was introduced in 1992 and became generally available nationwide by 1995. Connection to an SMDS service can be made from a variety of devices, including bridges, routers, CSU/DSUs as well as via frame relay and ATM networks. SMDS can employ various networking technologies. Early implementations use the IEEE 802.6 DQDB MAN technology at rates up to 45 Mbps. Data is framed for transmission using the SMDS Interface Protocol (SIP), which packages data as Level 3 Protocol Data Units (L3_PDU). The L3_PDU contains source and destination addresses and a data field that holds up to 9188 bytes.

ATM (Asynchronous Transfer Mode)

A network technology for both LANs and WANs that supports realtime voice and video as well as data. The topology uses switches that establish a logical circuit from end to end, which guarantees a quality of service (QoS) for that transmission. However, unlike telephone switches that dedicate circuits end to end, unused bandwidth in ATM's logical circuits can be appropriated whenever available. For example, idle bandwidth in a videoconference circuit can be used to transfer data. ATM is also highly scalable and supports transmission speeds of 1.5, 25, 100, 155, 622 and 2488 Mbps. ATM is also running as slow as 9.6 Kbps between ships at sea. An ATM switch can be added into the middle of a switch fabric to enhance total capacity, and the new switch is automatically updated using ATM's PNNI routing protocol.
Cell Switching
ATM works by transmitting all traffic as fixed-length, 53-byte cells. This fixed unit allows very fast switches to be built, because the processing associated with variable-length packets is eliminated (finding the end of the frame). The small ATM packet also ensures that voice and video can be inserted into the stream often enough for realtime transmission.
Quality of Service (Qos)
The ability to speficy a quality of service is one of ATM's most important features, allowing voice and video to be transmitted smoothly. Constant Bit Rate (CBR) guarantees bandwidth for realtime voice and video. Available Bit Rate (ABR) adjusts bandwidth according to congestion levels for LAN traffic. Unspecified Bit Rate (UBR) provides a best effort for remote users. Realtime variable Bit Rate (rt-VBR) supports interactive multimedia that requires minimal delays, and non-realtime variable bit rate (nrt-VBR) is used for bursty transaction traffic.
Integration with Legacy LANs
Network applications use protocols, such as TCP/IP, IPX, AppleTalk and DECnet, and there are tens of millions of Ethernet and Token Ring clients in existence. ATM has to coexist with these legacy protocols and networks. MPOA is an ATM standard that routes legacy protocols while preserving ATM quality of service. LANE (LAN Emulation) interconnects legacy LANs by encapsulating Ethernet and Token Ring frames into LANE packets and then converting them into ATM cells. It supports existing protocols without changes to Ethernet and Token Ring clients, but uses MPOA route servers or traditional routers for internetworking between LAN segments.

MPOA (MultiProtocol Over ATM)

An ATM Forum standard that provides routing of legacy protocols (IP, IPX, etc.) over ATM networks. MPOA separates the routing processing from the actual forwarding. A route server performs the routing calculations and sends its results to the ATM switches and edge devices which perform high-speed forwarding of the packets.

PNNI (Private Network-to-Network Interface)

A routing protocol used between ATM switches in an ATM network. It lets the switches inform each other about network topology so they can make appropriate forwarding decisions. PNNI is based on the OSPF protocol, but also measures line capacities and delays rather than just simple cost metrics. Thus, ATM switches can dynamically reroute packets based on current line conditions.

OSPF (Open Shortest Path First)

A routing protocol that determines the best path for routing IP traffic over a TCP/IP network. OSPF is an interior gateway protocol (IGP), which is designed to work within an autonomous system. It is also a link state protocol that provides less router to router update traffic than the RIP protocol (distance vector protocol) that it was designed to replace.

RIP (Routing Information Protocol)

A simple routing protocol that is part of the TCP/IP protocol suite. It determines a route based on the smallest hop count between source and destination. RIP is a distance vector protocol that routinely broadcasts routing information to its neighboring routers and is known to waste bandwidth. AppleTalk, DECnet, TCP/IP, NetWare and VINES all use incompatible versions of RIP.

IGP (Interior Gateway Protocol)

A broad category of routing protocols that support a single, confined geographic area such as a local area network (LAN). Contrast with EGP.

EGP (Exterior Gateway Protocol)

A broad category of routing protocols that are designed to span different autonomous systems. Contrast with IGP.

IGRP (Interior Gateway Routing Protocol)

A proprietary routing protocol from Cisco that was developed in 1988 to overcome the shortcomings of RIP. IGRP takes bandwidth, latency, reliability and current traffic load into consideration. It is typically used within an autonomous system, such as an Internet domain. IGRP was superseded by Enhanced IGRP (EIGRP), which provides enhancements such as the ability to detect a loop in the network.

AppleTalk

Apple's local area network architecture introduced in 1985. It supports Apple's proprietary LocalTalk access method as well as Ethernet and Token Ring. The AppleTalk network manager and the LocalTalk access method are built into all Macintoshes and LaserWriters. With other products from Apple and third parties, AppleTalk can run in PCs, VAXs and UNIX workstations. Since AppleTalk is patterned after the OSI model, it is a routable protocol that contains a network layer (OSI layer 3).

DECnet

Digital's communications network, which supports Ethernet-style LANs and baseband and broadband WANs over private and public lines. It interconnects PDPs, VAXs, PCs, Macs and workstations. In DECnet philosophy, a node must be an intelligent machine and not simply a terminal as in other systems. DECnet/DOS allows DOS machines to function as end nodes in DECnet networks, and DECnet/OSI is the implementation of DECnet Phase V that supports OSI and provides compatibility with DECnet Phase IV and TCP/IP.

LocalTalk

A LAN access method from Apple that uses twisted pair wires and transmits at 230,400 bps. It runs under AppleTalk and uses a daisy chain topology that can connect up to 32 devices within a distance of 1,000 feet. Third party products allow it to hook up with bus, passive star and active star topologies. Apple's LocalTalk PC Card lets a PC gain access to an AppleTalk network.

VINES (VIrtual NEtworking System)

A UNIX System V-based network operating system from Banyan Systems Inc., Westboro, MA, that runs on DOS and OS/2-based servers. It provides internetworking of PCs, minis, mainframes and other computer resources providing information sharing across organizations of unlimited size. Incorporating mainframe-like security with a global directory service called Streettalk, VINES allows access to all network users and resources. Options include printer sharing, e-mail, remote PC dial-in, bridges and gateways.

VAX (Virtual Address eXtension)

A family of 32-bit computers from Digital introduced in 1977 with the VAX-11/780 model. VAXes range from desktop personal computers to mainframes all running the same VMS operating system. Large models can be clustered in a multiprocessing environment to serve thousands of users. Software compatibility between models caused the VAX family to achieve outstanding success during the 1980s. VAXes also provide PDP emulation.

PDP (Programmed Data Processor)

A minicomputer family from Digital that started with the 18-bit PDP-1 in 1959. Its $120,000 price was much less than the million dollar machines of the time and 50 units were built. In 1965, Digital legitimized the minicomputer industry with the PDP-8, which sold for about $20,000. By the late 1970s, the PDP-8 processor was put on a single chip and used in DECmate workstations. Other PDPs were built, including 12-bit, 18-bit and 36-bit machines, the larger ones evolving into DECsystem models. In 1970, Digital introduced the 16-bit PDP-11, which became the most widely used minicomputer with more than 50,000 systems sold. The VAX series was introduced in 1977, but PDP machines lingered on for many years.

PC Card

A credit-card sized, removable module for portable computers standardized by PCMCIA. PC Cards are also known as "PCMCIA cards." PC Cards are 16-bit devices that are used to attach modems, network adapters, sound cards, radio transceivers, solid state disks and hard disks to a portable computer. The PC Card is a "plug and play" device, which is configured automatically by the Card Services software. All PC Cards are 85.6 mm long by 54 mm wide (3.37" x 2.126") and use a 68-pin connector. The original Type I card is 3.3 mm thick and is typically used to hold memory. Type II cards (5.0 mm thick) are commonly used for memory, modems and LAN adapters in laptops. Type III cards (10.5 mm thick) are used to hold a hard disk, wireless transceiver or other peripheral that needs more space. The Type III slot can hold two Type II cards. Toshiba introduced a 16 mm Type IV card, but this has not been officially adopted by the PCMCIA. Smaller cards will work in a Type IV slot.
Card and Socket Services
In order to use a PC Card slot in the computer, Card and Socket services must be loaded, typically at system startup. Card and Socket Services software is generally included with laptops that have PC Card slots. It also comes packaged with PC Cards. Card Services manage system resources required by the PC Card, and, on PCs, determines which IRQs and memory and I/O addresses are assigned. They also manage hot swapping and pass changes in events to higher-level drivers written for specific cards. Card Services talk to Socket Services, which is the lowest level of software that communicates directly with the PC Card controller chips. Socket Services can be built into the system BIOS or added via software.
CardBus
In early 1995, PCMCIA introduced the 32-bit CardBus standard. Although electrically different, the CardBus is architecturally identical to the PCI bus. The CardBus supports bus mastering and accommodates cards operating at different voltages. Its advanced power managment features allows the computer to take advantage of CardBus cards designed to idle or turn off in order to increase battery life. The CardBus specification allows data transfer up to 132 Mbytes/sec over a 33MHz, 32-bit data path.

PCMCIA (Personal Computer Memory Card International Association)

An international standards body and trade association that was founded in 1989 to establish a standard for connecting peripherals to portable computers. PCMCIA created the PC Card. For more information, visit www.pc-card.com.

DDS (Dataphone Digital Service)

An AT&T private line digital service with data rates from 2400 bps to 56Kbps. Private analog lines can be connected to DDS lines.

T1

A 1.544 Mbps point-to-point dedicated, digital circuit provided by the telephone companies. The monthly cost is typically based on distance. T1 lines are widely used for private networks as well as interconnections between an organization's PBX or LAN and the telco. The first T1 line was tariffed by AT&T in January 1983. However, starting in the early 1960s, T1 was deployed in intercity trunks by AT&T to improve signal quality and make more efficient use of the network. A T1 line uses two wire pairs (one for transmit, one for receive) and time division multiplexing (TDM) to interleave 24 64-Kbps voice or data channels. The standard T1 frame is 193 bits long, which holds 24 8-bit voice samples and one synchronization bit with 8,000 frames transmitted per second. T1 is not restricted to digital voice or to 64 Kbps data streams. Channels may be combined and the total 1.544 Mbps capacity can be broken up as required.

PBX (Private Branch eXchange)

An inhouse telephone switching system that interconnects telephone extensions to each other, as well as to the outside telephone network. It may include functions such as least cost routing for outside calls, call forwarding, conference calling and call accounting. Modern PBXs use all-digital methods for switching and can often handle digital terminals and telephones along with analog telephones.

CSMA/CD (Carrier Sense Multiple Access/Collision Detection)

The LAN access method used in Ethernet. When a device wants to gain access to the network, it checks to see if the network is free. If it is not, it waits a random amount of time before retrying. If the network is free and two devices access the line at exactly the same time, their signals collide. When the collision is detected, they both back off and each wait a random amount of time before retrying.

CLEC (Competitive Local Exchange Carrier)

An organization offering local telephone services. Although most CLECs are established as a telecommunications service organization, any large company, university or city government has the option of becoming a CLEC and supplying its own staff with dial tone at reduced cost. It must have a telephone switch, satisfy state regulations, pay significant filing fees and also make its services available to outside customers. This was all sanctioned by the Telecommunications Act of 1996. Contrast with ILEC.

ILEC (Incumbent Local Exchange Carrier)

A traditional local telephone company such as one of the Regional Bell companies (RBOCs). Contrast with CLEC.

ELEC (Enterprise LEC)

An organization that is large enough (about 2500 or more employees) to file for CLEC status and become its own customer. As a CLEC, it can purchase telephone service at wholesale rates that it can sell to itself as well as to others to further reduce costs. The Yankee Group coined the term.

LEC (Local Exchange Carrier)

An organization that provides local telephone service, which includes the RBOCs, large companies such as GTE and hundreds of small, rural telephone companies. A LEC controls the service from its central office (CO) to subscribers within a local geographic area.

DSL (Digital Subscriber Line)

A technology that dramatically increases the digital capacity of ordinary telephone lines (the local loops) into the home or office. DSL speeds are very much tied to the distance between the customer and the telco central office. The technology is geared to Internet access with its asymmetric versions (faster downstream than upstream) and short haul connections with symmetric versions (same rate coming and going). Unlike ISDN, which is also digital but travels through the switched telephone network, DSL provides "always-on" operation. At the telco central office, DSL traffic is aggregated in a unit called the DSL Access Multiplexor (DSLAM) and forwarded to the appropriate ISP or data network. Although DSL technologies are just emerging, there have been more versions and alphabet soup than most any other new transmission technology. The widely-touted Asymmetrical DSL (ADSL) is available in two modulation schemes: Discrete Multitone (DMT) or Carrierless Amplitude Phase (CAP). DMT is expected to prevail. ADSL and its variants can share the same line as the telephone, because they use higher frequencies than the voice band. However, a POTSsplitter must be installed on the customer's premises to separate the line between voice and ADSL. A version of ADSL, known as G.lite or Universal ADSL (also ADSL Lite and splitterless ADSL), eliminates the splitter, but other phones on the line may have to plug into low-pass filters to isolate them from the ADSL frequencies. Stay tuned! CDSL (Consumer DSL) is an asymmetric flavor that supports regular 56 Kbps V.90 modem access if ADSL is not available. RADSL (Rate adaptive DSL) adjusts speeds based on signal quality. IDSL (ISDN DSL) merely provides ISDN speeds. It does not support voice or go through the switched telephone network as does ISDN. HDSL (High Bit Rate DSL) has been the most widely-used DSL technology, providing T1 speeds over existing twisted pair without requiring the additional provisioning required for setting up T1 circuits. SDSL (Single Line DSL) is an HDSL variation that uses only one pair of cables instead of two. HDSL and SDSL cannot share lines with telephones. VDSL (Very High Bit Rate DSL) is expected to be used as the final drop from a fiber optic junction point to nearby customers. VDSL's extremely high capacity would let an entire apartment or office complex obtain high-bandwidth services using existing copper wires without having to replace the entire infrastructure with optical fiber. Like ADSL, VDSL can share the line with the telephone.
ASYMMETRIC DSL (Can share telephone line)
Type Upstream Downstream Pairs Cable Distance (ft)
ADSL 64-800 Kbps 0.5-8 Mbps 1 12-18000
ADSL Lite 64-384 Kbps 1-1.5 Mbps 1 22-25000
CDSL 128 Kbps 1 Mbps 1 12-18000
RADSL 128-1024 Kbps 0.6-7 Mbps 1 18-25000
VDSL 1.6 Mbps 13 Mbps 1 1000-4500
  3.2 Mbps 26 Mbps 1 1000-4500
  6.4 Mbps 52 Mbps 1 1000-4500
SYMMETRIC DSL (Cannot share telephone line except for VDSL)
Type Upstream & Downstream Pairs Cable Distance (ft)
HDSL 768 Kbps 2 12000
  1.544 Mbps (T1) 2 12000
  2.048 Mbps (E1) 3 12000
HDSL-2 1.544 Mbps (T1) 1 12000
  2.048 Mbps (E1) 1 12000
SDSL 384 Kbps 1 5-10000
  768 Kbps 1 5-10000
IDSL 144 Kbps 1 18000
VDSL** 26 Mbps 1 1000-4500
**can share telephone line

ATU (ADSL Transceiver Unit)

A device that provides ADSL (see DSL) modulation of the telephone line. The device at the telco side is the ATU-C (Central), which is a line card plugged into the DSLAM. The unit at the customer's side is the ATU-R (Remote), which is either an external modem or a card plugged into the PC.

V.90

An ITU standard (1998) for a modem that communicates at 56 Kbps downstream and 33.6 Kbps upstream. It is intended for use only with ISPs and online services that are digitally attached to the telephone system. Most service providers are typically connected with high-speed digital T1 or T3 circuits. In practice, the downstream link isn't generally faster than 45 Kbps in these PCM modems, so called because they use pulse code modulation downstream and standard V.34 upstream. Initially, two incompatible technologies competed in this arena: x2 from U.S. Robotics and K56Flex from Rockwell and Lucent. Such modems can be upgraded to V.90 if they contain software-upgradable memory chips.

MAPI (Mail API)

A programming interface that enables an application to send and receive mail over the Microsoft Mail messaging system. Simple MAPI is a subset of MAPI that includes a dozen functions for sending and retrieving mail.

TAPI (Telephony API)

A programming interface from Microsoft and Intel that is part of Microsoft's WOSA architecture. It allows Windows client applications to access voice services on a server. TAPI is designed to provide interoperability between PCs and telephone equipment, including phone systems and PBXs.

WOSA (Windows Open System Architecture)

An umbrella term for a variety of programming interfaces from Microsoft designed to provide application interoperability across the Windows environment. It provides a common denominator for front-end Windows applications to access back-end services from different vendors. For example, any WOSA-compliant query program from one vendor can gain access to any WOSA-compliant DBMS from any another vendor. See SPI. WOSA Interface Provides access to: ODBC Databases (DBMSs), MAPI Messaging systems, TAPI Telephone network services, LSAPI Software licensing, Windows SNA IBM SNA networks, Windows Sockets Internet, TCP/IP networks, Microsoft RPC Run remote procedures, Financial Services Banking services, WOSA/XRT News, stock market, etc.

SPI (Service Provider Interface)

The programming interface for developing Windows drivers under WOSA. In order to provide common access to services, the application (query, word processor, e-mail program, etc.) is written to a particular WOSA-supported interface, such as ODBC or MAPI, and the developer of the service software (database manager, document manager, print spooler, etc.) writes to the SPI for that class of service.

NetBIOS

The native networking protocol in DOS and Windows networks. Although originally combined with its transport layer protocol (NetBEUI), NetBIOS today provides a programming interface for applications at the session layer (layer 5). NetBIOS can ride over NetBEUI, its native transport, which is not routable, or over TCP/IP and SPX/IPX, which are routable protocols. NetBIOS computers are identified by a unique 15-character name, and Windows machines (NetBIOS machines) periodically broadcast their names over the network so that Network Neighborhood can catalog them. For TCP/IP networks, NetBIOS names are turned into IP addresses via manual configuration in an LMHOSTS file or a WINS server. There are two NetBIOS modes. The Datagram mode is the fastest mode, but does not guarantee delivery. It uses a self-contained packet with send and receive name, usually limited to 512 bytes. If the recipient device is not listening for messages, the datagram is lost. The Session mode establishes a connection until broken. It guarantees delivery of messages up to 64KB long.

WINS (Windows Internet Naming Service)

Name resolution software from Microsoft that runs under Windows NT Server and converts NetBIOS names to IP addresses. Windows machines are assigned NetBIOS names, which must be converted to IP addresses if the underlying transport protocol is TCP/IP.
Windows machines identify themselves to the WINS server, so that other Windows machines can query the server to find the IP address. Since, the WINS server is contacted by IP address, which can be routed across subnets, WINS allows Windows machines on one LAN segment to locate Windows machines on other LAN segments.
When a computer is moved to another subnet and a new IP address is assigned by DHCP, the WINS database is updated. WINS is used in a Windows network, and both DNS and WINS are used in a mixed environment. Microsoft's DNS server integrates the two systems. When a UNIX station wants to resolve the name for a PC, it queries the Microsoft DNS server, which in turn queries the WINS server if it does not already have it.

LDAP (Lightweight Directory Access Protocol)

A smaller X.500 directory service that provides authentication and certificate management.

cdmaOne™ 2G

A brand name, trademarked and reserved for the exclusive use of CDG member companies, that describes a complete wireless system that incorporates the IS-95 CDMA air interface, the ANSI-41 network standard for switch interconnection and many other standards that make up a complete wireless system.

cdma2000 3G (or Wideband cdmaOne)

A name identifying the TIA standard for third generation technology that is an evolutionary outgrowth of cdmaOne offering operators who have deployed a second generation cdmaOne system a seamless migration path that economically supports upgrade to 3G features and services within existing spectrum allocations for both cellular and PCS operators. The network interface defined for cdma2000 supports the second generation network aspect of all existing operators regardless of technology (cdmaOne, IS-136 TDMA, or GSM). This standard has been submitted by the TIA to the ITU as part of the IMT-2000 3G process. To gracefully migrate cdmaOne to cdma2000 capabilities offering advanced features to the market in a flexible and timely manner, implementation has been broken into evolutionary phases. The first phase capabilities have been defined in a standard known as 1XRTT. Scheduled for publication in the first quarter of 1999, 1XRTT introduces 144 kbps packet data in a mobile environment and speeds beyond this in a fixed environment. Features available with 1XRTT are a two-fold increase in both voice capacity and standby time, more than 300 kbps data capability, advanced packet data services, as well as greatly extended battery life and improved sleep mode technology. All of these capabilities will be available in an existing cdmaOne 1.25 MHz channel. cdmaOne evolution to the complete capabilities of cdma2000 will continue in phase two and incorporate the capabilities of 1XRTT, support all channel sizes (5 MHz, 10 MHz, etc.), provide circuit and packet data rates up to 2 Mbps, incorporate advanced multimedia capabilities, and include a framework for advanced 3G voice services and vocoders, including voice over packet and circuit data.

W-CDMA 3G (Wideband CDMA)

A name identifying the ETSI and NTT DoCoMo standards for third generation technology submitted to the ITU as part of the IMT-2000 3G process. This standard encompasses an air interface that uses the CDMA technique but it is not compatible as defined for both air and network interfaces with cdmaOne, cdma2000 or IS-136. The air interface specification is not compatible with GSM and therefore does not support evolutionary migration.

3G (third generation communication systems)

Capable of supporting higher data rates and multimedia.

CDMA (Code Division Multiple Access)

A digital cellular phone technology from Qualcomm, Inc., San Diego, CA, that operates in the 800MHz and 1.9GHz (PCS) bands. CDMA phones are noted for their excellent call quality and long battery life, and some phones can switch between both bands. CDMA uses a spread spectrum technique that codes each digital packet and allows multiple calls to be placed on one channel, boosting caller capacity 20 to 35 times that of the analog network. CDMA has become widely used in North America.


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