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An acronym for Layer 2 Forwarding (also known as level 2); a tunneling protocol from Cisco Systems. L2F has been submitted to the Internet Engineering Task Force (IETF) for approval as a standard. In addition, Northern Telecom Inc. (Nortel) and Shiva Corp. (Shiva is now owned by Intel) (Shiva), have all announced their support for L2F.


An acronym for Level 2. It is a designation of cache memory. Almost all current generation processors have the Level 2 (L2) Cache either in the same package module as the processor if not on the chip itself. Its size and speed must be taken into consideration. This is important because the most commonly used instructions can be stored there so the CPU doesn't have to reach into slower system memory to retrieve these most popular instructions. L2 cache is many times faster than system memory; therefore a CPU with little or no L2 cache is at a serious disadvantage. Often a smaller size cache can outperform a much larger one if the smaller one is significantly faster. This also depends on the CPU's instructions. With current processors the speed of the cache is either the same as the Megahertz (Mhz) of the CPU or half the speed of the CPU. Current sizes for L2 cache range from 128kb Celeron to 2 MB Pentium III (P3) and Xeon. To give you an understanding of how important the speed of the cache is we should look at the Celeron as opposed to the Pentium II (P2). The P2 and the Celeron share the same CPU core, the only difference being the way they use L2 cache. The Celeron has 128 kb of cache that runs at the full speed of the processor, while the P2 has 512 kb of cache that runs at half the speed of the processor. Even though the Celeron has 25% the amount of cache as the P2 it performs at a level almost identical to the P2 in cache operations.


An acronym for Layer 2 Switch (also known as level 2).


An acronym for Layer Two Tunneling Protocol (also known as level 2), an extension to the PPP protocol that enables ISPs to operate Virtual Private Networks (VPNs). L2TP merges the best features of two other tunneling protocols: PPTP from Microsoft and L2F from Cisco Systems. Like PPTP, L2TP requires that the ISP's routers support the protocl.


An acronym for Layer 3 Forwarding (also known as level 3); a tunneling protocol from Cisco Systems. L3F has been submitted to the Internet Engineering Task Force (IETF) for approval as a standard. In addition, Northern Telecom Inc. (Nortel) and Shiva Corp. (Shiva is now owned by Intel) (Shiva), as well as many other L2F supporting companies, have all announced their support for L3F.


An acronym for Layer 3 Switch (also known as level 3). Take a look at an interesting article on the subject from 3COM.


An acronym for Layer Three Tunneling Protocol (also known as level 3), an extension to the PPP protocol that enables ISPs to operate Virtual Private Networks (VPNs). L3TP merges the best features of three other tunneling protocols: PPTP from Microsoft, L2F and L3F both from Cisco Systems. Like PPTP, L2TP and L3TP require that the ISP's routers support the protocol.


See Local Area Network.


A set of protocols and syntax conditions that allow programming within a group on known conditions. Short (slang) for programming languages for more information.


A small portable computer; generally it is self contained.


An acronym for Light Amplification by the Stimulated Emission of Radiation. It is a device that creates a uniform and coherent light that is very different from an ordinary light bulb. The uses vary but in the computer industry, lasers are mainly used in networks as avenues for data transfer or lasers are the engine for many printers. Many lasers deliver light in an almost-perfectly parallel beam (collimated) that is very pure, approaching a single wavelength. Laser light can be focused down to a tiny spot as small as a single wavelength. Solid state lasers create the ultra-high-speed, minuscule pulses traveling in optical fibers traversing the backbones of all major communications networks. Light traveling in an optical fiber is impervious to external interference, a constant problem with electrical pulses in copper wire. In the case of printers, some new technology can put you in an awkward position. See details here.


1. A measure of the temporal delay. Typically, in xDSL, latency refers to the delay in time between the sending of a unit of data at one end of a connection, until the receipt of that unit at the destination. This is a frequent and important concern in satellite communications.
2. The amount of time that passes before something starts to happen after it has been given the instruction to start. An important technology consideration in any performance based evaluation, where high throughput computer devices often postpone transfers or other memory intensive actions based on internal decisions of protocol transaction overhead, device or software contention and other OS factors.


1. An imaginary line around the Earth parallel to the equator. Latitude is measured from the equator, with positive values going North and negative values going South. However, some databases do return South as positive. Be sure to verify on the legend of the map, information or database, which is positive.
2. The angular distance between an imaginary line around a heavenly body parallel to its equator and the equator itself.
3. Scope for freedom of e.g. action or thought; freedom from restriction. Freedom from normal restraints in conduct. Programmers love that one!

layer 2 switch

Please see L2S. Also see L2F and L2TP.

layer 3 switch

Please see L3S. Also see L3F and L3TP.


1. A particular form of video technology in portable devices, clocks, watches, and computing devices. An acronym for Liquid Crystal Display. LCD displays utilize two sheets of polarizing material with a liquid crystal solution between them. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal, therefore, is like a shutter, either allowing light to pass through or blocking the light. In clocks and counters that use LCDs, the pattern often emulates LEDs, though LCDs are NOT diodes. Monochrome LCD images usually appear as blue or dark gray images on top of a grayish-white background. Color LCD displays use two basic techniques for producing color, passive matrix is the less expensive of the two technologies. The other technology, called thin film transistor (TFT) or active matrix, produces color images that are as sharp as traditional CRT displays, but the technology is expensive. Recent passive matrix displays using new CSTN and DSTN technologies produce sharp colors rivaling active matrix displays. Most LCD screens used in notebook computers are backlit to make them easier to read.
2. An acronym for TV and early 2000s computer technology for flat screen displays. LCD monitors usually contain three separate LCD glass panels, one each for the red, green, and blue channels of the video signal being fed into the projector. As light passes through the LCD panels, individual pixels can be opened to allow light to pass or closed to block the light, either on or off. This activity modulates the light and produces the image that is projected onto the viewer's screen. The contrasting technology as of 2003 is DLP, and a quickly fading (no pun intended) hybrid technology called LCOS. See SDTV for more information.


An acronym for Liquid Crystal On Silicon, TV technology for flat screen displays; a technology that most major technology and equipment manufacturers have shunned after experimentation. It is kind of a hybrid of DLP, and LCD without some of the problems of either but also with the strong features of either. As of October 2004, Intel and early LCOS TV leading producer Phillips, have dropped the technology. See SDTV for more information.


This is an acronym for Lightweight Directory Access Protocol. It is a software protocol for enabling anyone to locate organizations, individuals, and other resources such as files and devices in a network, whether on the public Internet or on a corporate intranet. LDAP is a "lightweight" (smaller amount of code) version of Directory Access Protocol (DAP), which is part of X.500, a standard for directory services in a network. LDAP is lighter because in its initial version it did not include security features, an obvious shortcoming in today's world. LDAP originated at the University of Michigan and has been endorsed by at least 40 companies. Netscape includes it in its latest Communicator suite of products. Microsoft includes it as part of what it calls Active Directory in a number of products including Outlook Express. Novell's NetWare Directory Services interoperates with LDAP. Cisco also supports it in its networking products. In a network, a directory tells you where in the network something is located. On TCP/IP networks (including the Internet), the domain name system (DNS) is the directory system used to relate the domain name to a specific network address (a unique location on the network). However, you may not know the domain name. LDAP allows you to search for an individual without knowing where they're located (although additional information will help with the search). An LDAP directory is organized in a simple "tree" hierarchy consisting of the following levels:
1. The root directory (the starting place or the source of the tree), which branches out to
2. Countries, each of which branches out to
3. Organizations, which branch out to
4. Organizational units (divisions, departments, and so forth), which branches out to (includes an entry for)
5. Individuals (which includes people, files, and shared resources such as printers)

An LDAP directory can be distributed among many servers. Each server can have a replicated version of the total directory that is synchronized periodically. An LDAP server is called a Directory System Agent (DSA). An LDAP server that receives a request from a user takes responsibility for the request, passing it to other DSAs as necessary, but ensuring a single coordinated response for the user.


An acronym for Light Dependent Resistor. This is a special type of resistor and is sometimes called a photoconductor. LDRs are made so that their resistance decreases as the level of light falling on them increases.

leased line

A permanently established connection between computers over a dedicated phone line which is leased from a telephone carrier. See also dedicated line.


A telephony acronym for Local Exchange Carrier. An LEC is a company that provides intra-LATA (local exchange carrier) telecommunications services, like Verizon or Bell South.


1. An industry acronym for Light Emitting Diode. These are usually small little "bulbs" that glow in different colors (though usually red, blue, green or orange, all of which are problems to color blind people) when they are "turned on" (conduct current as a diode).
2. The generic term used for the lighted display on calculators and other numeric displays; they are made up of 7 distinct straight line "bar" diodes that when turned on display light in a "portion of a line" (instead of a dot) pattern. The pattern combinations can be turned on or off (does not conduct current) to form numbers or in some cases, alphanumeric characters. Some of these had an 8th "light" which was a decimal. LCDs emulate this pattern style, though they are NOT diodes. The first to use the style was the "nixie" tube from the early 50's. The pattern is still in use today, though nixies have gone to the vacuum tube graveyard. You can see our emulations of the LED style in our digital countdown timer and clock, or the clock or digital countdown timer individually.


A kind name for the historical or "old way" to do something in computers. (A nice way to say outdated and archaic.) Generally associated with Windows systems that refer to a DOS method or procedure. A DOS version of a program; sometimes associated with a COBOL programmer.

level 2 switch

Please see L2S. Also see L2F and L2TP.

level 3 switch

Please see L3S. Also see L3F and L3TP.

lexical scoping

Lexical scoping, often known as static scoping, is a style used in several programming languages that determines the definition and functionality of a variable so that it may only be recognized, utilized and accessed from inside the block of code in which it is defined. Some languages define it as a local variable while other variables are global. The scope is determined when the code is compiled as opposed to run time. A variable declared in this fashion is sometimes called a non-public variable. The opposite approach is known as dynamic scoping. Dynamic scoping creates variables that can be called from outside the block of code in which they are defined. A variable declared in this fashion is sometimes called a public or global variable.


Libraries are home to collections of programs, graphics, and other files related to the specific forum the library is located in. For a complete listing of files available on your service, a search for LIBRARY usually yields many options. Libraries are often used by programmers for common routines or subroutines that are called. In Windows architecture, call routines are in library files resident on your drive called dynamic link libraries, or as often called, DLLs.


This is an acronym used in accounting, inventory control and computer server buffering and cache technology, Last In First Out. In the world of computers, LIFO is seldom used in buffering and cache operations. In programming memory management, it means that instructions last placed in the Queue are handled in an order that is on a most recent request or instruction, first served basis, working backwards until caught up with the demand. This is most often used in computers in handling of memory stacks. Most computers use the opposite which is FIFO.


A technology that speeds the copying of information from main memory to CD-ROM. The conventional process for copying to CD-ROM, called magnetic-optico (MO) technology, requires that the disk pass at least twice under the head; once for erasing and once for copying (also called writing). LIMDOW modulates the laser's intensity for both processes to complete the writing in a single rotation.


1. A connection of some sort. This can be a phone line (POTS), a network cable line, and electrical power line. Often used in slang for the electrical trace paths on boards and computer cards. See leased line and dedicated line. Also see line filter and line noise.
2. A kind of high speed printer, usually associated with minicomputers and mainframes. It prints a line at a time from the buffer. Usually associated with band printing and dot matrix technology.
3. The thing that forms behind Bill Gates as he makes his daily Windows deposit at the bank. (Why do you think it is called a teller Window?)


1. A particular type of amplifier of RF and electrical signals. Slang term for an illegal CB amplifier.
2. A repeating calculable process.
3. A relationship between input and output in which the output varies in direct proportion to the input.

line filter

1. A device to trap and suppress analog and electrical spikes on either electrical or telephone lines. All spikes and noise show up in the form of electrical impulses. Clearing out the offending ones can often stabalize the operating conditions of a computer and/or modem.
2. Something often needed in singles' bars.

line noise

1. Noise or static on a phone line that can interfere with modem communications. Line noise is not always audible. Line noise can be inside or outside of your facility but that located or sourced outside can only be corrected by your phone company (Telco). Bad connections or loose connections are the normal cause of noise inside a user's facility. The term noise is associated with interference.
2. Noise or static on an electrical line or network line; can cause the system to lock up or crash. Some electrical line filters trap this kind of interference.


A highlighted word or picture within a hypertext document that when clicked bring you to another place within the document or to another document altogether. See also hyperlink. The term is often associated with the idea of a door to another site.


A list box on your ISP's service is a collection of links to web sites, ISP sites, chat rooms, message boards, software libraries, folders, documents, etc.


An Internet mailing list manager for E-Mail. All ISPs have some form of this.

list server

An automated mailing list distribution system. List servers maintain a list of E-Mail addresses to be used for mass E-Mailing. Subscribing and unsubscribing to the list is accomplished by sending a properly formatted E-Mail message to the list server.


An abbreviation of local loop in telephony.


An acronym for Logical Link Control. It is the higher of the two data link layer sublayers defined by the IEEE. The LLC sublayer handles error control, flow control, framing, and MAC sublayer addressing. The most prevalent LLC protocol is IEEE 802.2, which includes both connectionless and connection oriented variants. It now has further extensions and is called LLC2. The lower of the sublayers is media access control, MAC. See also application layer, MAC, network layer, physical layer, PQ, presentation layer, session layer, and transport layer.


An acronym for Logical Link Control, type 2. It is an extension of the connection oriented OSI LLC sublayer protocol. This is the current standard for LLC activity. See also application layer, MAC, network layer, physical layer, PQ, presentation layer, session layer, and transport layer.


A clock timer chip, made originally by Signetics, but now multi-sourced by National Semiconductor. See 555.


An acronym for Local Multipoint Distribution Services. This is a fixed point (non-mobile) wireless technology that operates in the 28 GHz band and offers line of sight coverage over distances up to 5 kilometers. It can deliver data and telephony services to 80,000 customers from a single node. LMDS is one solution for bringing high bandwidth services to homes and offices within the "local loop or last mile" of connectivity, an area where broadband cable or optical fiber may not be convenient or economical. Data transfer rates for LMDS can reach 1.5 Gbps to 2 Gbps, but a more realistic value may average downstream around 38 Mbps. See MMDS.

Lobby or Center

The main screen of the ISP service, the main chat and contact area.

Local Area Network - LAN

A group of computers at a single location (usually an office or home) that are connected by phone lines, network cables of various configurations or coaxial cable. Usually controlled and administered by the Sysop, system operator, or Admin, the network administrator. The current popular software for LANs is Novell and NT. Most are run on an Ethernet protocol but there are other options.

local loop

A generic term for the connection between the customerís premises (home, office, etc.) and the providerís serving central office (CO). Historically, this has been a wire line connection; however, wireless options are increasingly available for local loop capacity. Also colloquially referred to as "the last mile" (even though the actual distance can vary greatly).

Locate Member Online

An ISP feature that allows you to search for a member online. If the member is in a chat room, you will be informed which one.


1. This is one of the basic functions of multi-users systems. File locking is a critical in all multi-user computer systems, including LANs and WANs. When users share files, the operating system must maintain file integrity in that more than one user can not change or modify the same file simultaneously. It does this by locking the file to modification as soon as the first user opens it. However, all subsequent users may read the file, but they cannot write to it until the first user is finished. Even then, the operating system must recognize in a real-time environment that a user has relinquished control of the file and allow the next prioritized user to gain control. The process can be refined even more to the record level. In addition to file locking, many current database management systems, designed for multiple users, support record locking, in which a single record, rather than an entire file, is locked. This enables different users to access different records within the same file without interfering with one another. In very technically sophisticated database systems, the process can even go to the field level of a record. This however, is no longer a function of only the operating system. This is intrinsic to the software routines enabling the function within the database.
2. To make a file or other piece of data inaccessible.
3. A piece of hardware, often called a dongle or a pico, that must be accessed in order to gain permission to use a piece of software.
4. A software routine that maintains that in a multi-user environment, up to a maximum number of users can use a particular licensed program.
5. In Macintosh environments, locking a diskette means write-protecting it.
6. To keep a user from logging into a server or system.


The logging feature of some ISP's allows you to save all the text that appears on your screen to a text file that you can read offline. The 'chat' log option saves only the text from chat rooms and auditoriums. The 'session' log option saves all text that appears on your screen.


1. The study of the principles of reasoning, especially of the structure of propositions as distinguished from their content and of method and validity in deductive reasoning. The ability to make a decision.
2. A system of calculated reasoning, Aristotle's logic.
3. A mode of intense reasoning, such as, by that logic of earthquakes, we should plan for Palm Springs, CA to be beach front property.
4. The formal, guiding principles of a discipline, school, or science.
5. Valid reasoning, such as, your white paper lacks the logic to prove your theory of non-conductive electron flow.
6. The relationship between elements; and between an element and the whole in a set of objects, individuals, principles, or events, such as, there's a certain logic to the motion of rush-hour traffic. That logic definition suggests a repetitive nature, such that selections made once by logic will be made the same always, unless changes are made to the selection criteria.
7. In computer sciences, the non-arithmetic operations performed by a computer, such as sorting, comparing, and matching, that involve yes-no decisions. This is often termed programming logic. See Boolean.
8. In computer circuitry, a graphic block representation of computer circuitry. The idea is often called computer logic.

logic board

1. A physical diagram or chart showing the flow or decision making process of a program. Sometimes it is termed a flow chart. See logic.
2. A piece of computer hardware. See ALU.


1. A term used to describe the process of registering with an ID, name or number and a password combination to a server or service.
2. The actual ID assigned to use to attach yourself to a server or service. See username.


Laugh(ing) Out Loud, an example of online shorthand used in chat rooms and in E-Mail.


An imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator; all points on the same meridian have the same longitude. A line of longitude is often called a meridian, as in the prime meridian, the line that divides East from West. Longitude is measured from the Prime Meridian (which is the longitude that runs through Greenwich, England, the zero point of time measurement), with positive values going east and negative values going west. However, some databases do return West as positive. Be sure to verify on the legend of the map, information or database, which is positive.


1. A term used in slang to say a disk drive is being read. The system is looking. Also the term used for visiting your local computer store with a credit card that is already to the max.
2. Singles' bar activity.


A programming technique of creating a series of repeating actions. Usually, there is some event specified as part of the loop which triggers the ending of the repetitious action. A frequent error condition is known as "endless loop", where an action is repeated but there is not exit.

loop back test

Any test in which a test signal is injected at one end of a circuit, is looped back at the other end, and monitored at the originating end.

loop current

Depending on the Telco, loop current is typically 20 to 50 Ma (milliamps). Current that flows from the CO when a telecom device goes off hook.

loop start line

A type of calling signal that relies on a telecom device to allow DC current to flow when it goes into an off hook condition. The CO or PABX senses this current and intercepts it as a request for service. Also known as "POTS".


Loran-C, Long Range Navigation time, is an atomic time scale implemented by the atomic clocks in Loran-C chain transmitter sites for navigation systems. Loran time was zero at 0h 1-Jan-1958 and since it is not affected or altered by leap seconds it is now ahead of UTC by 22 seconds, as of this update. Check our Multiple Time Display Converter for current changes.


A communications abbreviation for Line Of Sight.


The zero voltage state in a logic circuit. Though it may not be actually zero, it is considered a logical zero. In TTL circuits, it is below 2.4 volts but the input sinks or draws current. In CMOS designs, it is below 3.2 volts and the input does NOT sink current. The supply voltage is assumed to be 5 volts.

low level format

The native format of the hard disk drive, based on the maximum speed and size available. Usually the condition the drive is in when shipped from the factory. In some cases, there is also a second, high level format.

low level language

A machine language or an assembly language. Low-level languages are closer to the hardware than are high-level programming languages, which are closer to human languages. High-level languages are reduced, interpretted or compiled to communicate with the hardware.


An acronym for Low-Pass Filter. A signal filter which would be installed in a customer premises ADSL modem (ATU-R), which would not modify the low frequencies present in its input signal (the POTS transmission is sent unmodified to a phone), but does prevent the high frequency components (data) from reaching a customerís telephone. See High-Pass Filter (HPF).


An abbreviation for Low Power Radio Service. See our frequency table and additional information and our Citizens Band Radio (CB) Frequency Table.


A motherboard form factor used in some desktop model PCs. This type motherboard was really popularized by the now defunct (an rightly so...) Packard Bell company during the 386 and 486 days. Partner NEC also had a heavy usage. Compact and IBM gave an attempt also but felt that speed and poor electrical contact were problems that could not be easily resolved in the design. The distinguishing characteristic of LPX is that expansion boards are inserted into a riser that contains several slots. So the expansion boards are parallel to the motherboard rather than perpendicular to it as in other common form factors, such as AT and ATX. The LPX design allows for smaller cases, but the number of expansion boards is usually limited to two or three. The LPX form factor has been gradually replaced by NLX.

LTNS (Long Time No See)

Long Time No See, a form of online shorthand commonly seen in chat rooms and E-Mail.


The industry name for communications giant Lucent Technologies. See them at WWW.LUCENT.COM.


To hang out in an area without directly participating. For example, when you're new to a discussion group or chat room, it's a good idea to lurk and become familiar with its scope and general rules before posting. Lurking is perfectly acceptable in cyberspace; the negative connotations of the standard English usage does not always apply, though it can. See also "delurk". A lurker is one who sits in a chat room, yet does not participate. To lurk is the process of sitting in the shadows. Who knows what evil... See hacker and wannabe.

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