J

Java
Java is an interpreted, platform-independent, high-level programming language developed by Sun Microsystems. Java is a powerful language with many features that make it attractive for the Web.

JavaScript
JavaScript is an interpreted, client-side scripting language developed by Netscape. All major browsers offer built-in support for JavaScript, and can interpret blocks of JavaScript code embedded in an HTML page. An international open standard called ECMAScript is based on JavaScript.

Jitter
A signal distortion caused when a carrier signal is not synchronized to its reference timing positions is referred to as jitter. Jitter can cause transmission errors and loss of synchronization for high-speed synchronous communication links.

JScript
As Microsoft's implementation of ECMAScript, JScript is the international standard based on Netscape's JavaScript. JScript is natively supported by Microsoft ASP, and is preferred for writing ASP client-side script blocks.

Joint Photographic Experts Group (JPEG)
JPEG is an open standard that defines a method of compressing still images. See JPEG File Interchange Format.

JPEG File Interchange Format (JFIF)
JFIF is a public domain graphic compression format that conforms to the JPEG standard for image compression. It is one of two popular graphic image formats used in HTML pages (GIF is the other). JPEG/JFIF files offer higher resolution, with up to 16.7 million colors, and are generally used in continuous-tone images such as photographs. However, JPEG/JFIF compression is lossy; even at the highest quality setting, some image information is lost.

K

Kludge
Kludge (pronounced "klooj") is an ugly solution to a technical problem, often using techniques or hardware to do jobs they were not designed for. Kludge is a last-ditch approach that gets a job done, but it is not something to be proud of. See hack.

L

LAN
A LAN is a grouping of computers via a network, typically confined to a single building or floor of a building.

LAN Emulation (LANE)
LANE is a standard, developed by the ATM Forum, that allows connection-oriented ATM to interoperate with existing equipment that supports connectionless LAN protocols such as Ethernet. ATM-attached devices can form LANE services that operate as VLANs within a connectionless LAN. Each of the LANE services (or emulated LANs) includes multiple LE clients, a single LE server, and a single BUS.

LAN Emulation Client (LEC)
An LEC is a process residing in an ATM end system that is a member of an emulated LAN, or LANE service. Each LE client is identified by a 48-bit MAC address, and provides MAC-level emulation of an Ethernet or Token Ring LAN ser­vice to higher layer protocols. See ATM, LANE, and LES.

LAN Emulation Server (LES)
LES is a process residing in an ATM system that provides the control functions necessary for an emulated LAN, or LANE service. LES may be implemented in an ATM-attached server, router, or switch, and may be centralized or distributed throughout the network. An LES registers and resolves MAC addresses to ATM addresses. When an LEC joins an emulated LAN, it registers its LAN destination with the LES, mapping its MAC address to its ATM address. See ATM, LANE, and LEC.

Latency
Latency is the transmission delay created as a device processes a frame or packet. It is the duration from the time a device reads the first byte of a frame or packet, until the time it forwards that byte.

Laser
The term laser is an acronym that stands for Light Amplification by Stimulated Emission of Radiation. A laser creates a very narrow beam of light that consists of 1 wavelength. The waves of this light are radiated "in phase," or are perfectly aligned with each other. This purity and alignment, called coherence, makes laser light very powerful and efficient; a beam of laser light can travel extremely long distances without dispersing.

Light Emitting Diode (LED)
LED is an electronic component that emits light when an electrical signal flows through the component. LEDs are used, for example, to indicate network activity for a networking device such as a hub, or as a light source for fiber optic cable (multimode) implementations.

Link Control Protocol (LCP)
LCP is a transmission protocol used by PPP to set up and test a serial connection.

Link Segments
Segments of cable, without nodes attached, used to extend the length of an Ethernet network are referred to as link segments.

Load Balancing
Spreading processing work or communications requests evenly across multiple devices or communications links is referred to as load balancing. For example, large Web sites use two or more identical Web servers, and use load balancing to divide the work among them.

Lobe
A lobe is a single loop of a Token Ring network. A Token Ring network can contain many individual lobes. The lobe wire connects the token ring node to the hub/MAU.

Local Area Network (LAN) Segment
A LAN segment is a section of a network connected to a bridge, switch, or router port.

Local Exchange Carrier (LEC)
See below.

Local Exchange Carrier
A local exchange or central office (CO) is a telephone company facility where local loops are terminated. The function of a CO is to connect individual telephones through a series of switches. COs are tied together in a hierarchy for efficiency in switching. Other terms for CO are wiring center, and public exchange.

Local Loop
A local loop is a span of copper cabling that exists between a telephone subscriber and the closest telephone office (local exchange).

Logical Link Control (LLC)
LLC is a Data Link Layer protocol used to control the flow of information across a physical link. LLC is often used in Ethernet networks that use the Institute of Electrical and Electronics Engineers (IEEE) frame type, which does not include a type field.