Transcript الشريحة 1

A local area network (LAN) is a group of
computers and associated devices that
share a common communications line or
wireless link. Typically, connected
devices share the resources of a single
processor or server within a small
geographic area (for example, within an
office building). Usually, the server has
applications and data storage that are
shared in common by multiple computer
users. A local area network may serve as
few as two or three users (for example, in
a home network) or as many as
thousands of users (for example, in an
FDDI network
A metropolitan area network (MAN) is a network that
interconnects users with computer resources in a
geographic area or region larger than that covered
by even a large local area network (LAN) but smaller
than the area covered by a wide area network (WAN).
The term is applied to the interconnection of
networks in a city into a single larger network (which
may then also offer efficient connection to a wide
area network). It is also used to mean the
interconnection of several local area networks by
bridging them with backbone lines. The latter usage
is also sometimes referred to as a campus network.
A wide area network (WAN) is a computer network that covers a
broad area (i.e. any network whose communications links cross
metropolitan, regional, or national boundaries [1]). Less formally, a
WAN is a network that uses routers and public communications
links. Contrast with personal area networks (PANs), local area
networks (LANs), campus area networks (CANs), or metropolitan
area networks (MANs), which are usually limited to a room, building,
campus or specific metropolitan area (e.g., a city) respectively. The
largest and most well-known example of a WAN is the Internet. A
WAN is a data communications network that covers a relatively
broad geographic area (i.e. one city to another and one country to
another country) and that often uses transmission facilities provided
by common carriers, such as telephone companies. WAN
technologies generally function at the lower three layers of the OSI
reference model: the physical layer, the data link layer, and the
Like the familiar Local Area Network (LAN) used to connect computers
within an office or building, a Small Area Network (SAN) is used to
connect Integrated Circuit (IC) components on a printed circuit board, or
within a box or system. Due to its low cost, flexibility, and space saving
characteristics, Small Area Networks provide device control, media
security, and health monitoring connectivity in electronic products
ranging from cell phones, to PCs, to large computer server system.
Small Area Networks typically include one or more master devices that
communicate with one or more slave devices using a serial (one bit at a
time) protocol over a common wire bus that connects all the devices
together. A master can get the attention of a slave device by sending the
slave address over the common wire bus, or by applying a signal to
separate device select lines.
There are a wide variety of Small Area Networks in use today. These
include Inter-Intergrated Circuit Bus (I2C Bus), System Management Bus
(SMBus), Serial Peripheral Interface (SPI), 1-Wire, and more. Each bus
type offers characteristics such as cost and flexibility that can make it
better suited to specific applications
A data center (sometimes spelled datacenter) is a
centralized repository, either physical or virtual, for the
storage, management, and dissemination of data and
information organized around a particular body of
knowledge or pertaining to a particular business. The
National Climatic Data Center (NCDC), for example, is a
public data center that maintains the world's largest
archive of weather information. A private data center
may exist within an organization's facilities or may be
maintained as a specialized facility. According to Carrie
Higbie, of Global Network Applications, every
organization has a data center, although it might be
referred to as a server room or even a computer closet.
In that sense, data center may be synonymous with
network operations center (NOC), a restricted access
area containing automated systems that constantly
monitor server activity, Web traffic, and network
performance