Over the past couple of decades communication
has evolved from postage and telephone to connecting with each other
instantaneously. In the past businesses
have used basically two types of networks—telephone networks and computer
networks. Now these two networks are
merging into one Internet-based technology network.
A simple computer network consists of two or
more computers, a network operating system residing on a dedicated server
computer, wiring connecting the devices, network interface cards (NICs),
switches, and a router. A network
operating system (NOS) directs and manages communications on the network and
coordinates network resources. A server
computer is a computer on a network that performs important network functions
for client computers. Network interface
cards are cards in a computer that enable it to connect to the network. A router is a communications processor used
to move packets of data through different networks making sure it reaches the
correct address. By linking many small local
area networks to other local area networks and to business-wide corporate
networks, a network infrastructure for a large corporation is formed.
Contemporary networks and the Internet are
shaped on three main technologies:
client/server computing, packet switching, and TCP/IT and
connectivity. Client/server computing is
a distributed computing model where some of the processing power is located
within small, inexpensive client computers.
Packet switching is where data is grouped into small packets, which are
transmitted independently over various communications channels and reassembled
at their final destination. Transmission
Control Protocol/Internet Protocol (TCP/IP) transmits data among different
types of computers over long distances.
A protocol is a set of rules and procedures governing transmission of
information between two points in a network.
TCP establishes a connection between the computers, sequences the
transfer of packets, and acknowledges the packets sent. IP is responsible for the delivery of packets
and includes the dissembling and reassembling of packets during transmission.
Two ways to communicate a message in a network
are by analog signal or digital signal.
An analog signal is characterized by a continuous waveform that passes
through a communications medium and has been used for voice communication,
e.g., telephone handset, speaker on computer, iPod earphone. A digital signal is a discrete, binary
waveform that communicates information as strings of two discrete states—one bit
and zero bits. A modem converts digital
signals from a computer into analog signals that can be sent over and/or
received from telephone lines, cable lines, or wireless media that use analog
signals.
One way to classify networks is according to
their geographic range. Local Area
Networks (LANs) are designed to connect personal computers and other digital
devices that are within close range of each other. They are also able to link long-distance
networks using the Internet. LANs are
sometimes described by their topologies (the way their components are connected
together). A star topology is where all
devices on the network connect to a single hub.
A bus topology is where one station transmits signals, which travel in
both directions along a single transmission segment. A ring topology connects network components
in a closed loop. Another type of
network based on geographic range is a wide area network (WAN). These networks span over a larger
geographical range. The Internet is the
most useful WAN. WANs connect computers
through public networks or through leased lines or satellites. A metropolitan area network (MAN) spans over
an area between a LAN and a WAN.
Networks use different types of physical
transmission media. Twisted wire
consists of strands of copper wire twisted in pairs. It is an older type of transmission
medium. Coaxial cable consists of
thickly insulated copper wire than can transmit a larger volume of data than
twisted wire. It is used today for
longer runs in large buildings.
Fiber-optic cable consists of bound strands of clear glass fiber. It is much faster, lighter, and more durable
than wire media, and it is well suited for systems that transfer large volumes
of data. Wireless transmission media is
based on radio signals of various frequencies.
Three types are microwave, cellular, and Wi-Fi.
The Internet is a worldwide network of
networks. It is based on the TCP/IP
networking protocol. Each computer is
assigned an Internet Protocol (IP) address indicating a unique computer
location on the Internet. The Domain
Name System (DNS) converts domain names to IP addresses. The domain name is the English-like name that
corresponds to the unique IP address number.
Worldwide Internet policies are established by a number of professional
organizations and government bodies, including the Internet Architecture Board
(IAB), which helps define the overall structure of the Internet; the Internet
Corporation for Assigned Names and Numbers (ICANN), which assigns IP addresses;
and the World Wide Web Consortium (W3C), which sets Hypertext Markup Language
and other programming standards for the web.
These organizations help to keep the Internet operating as efficient as
possible.
The Internet is based on client/server
technology. Individuals using the
Internet control what they do through client applications on their
computer. In turn the client uses the
Internet to request information from a particular Web server on a distant
computer, and the server sends the requested information back to the client
over the Internet. Client programs
include PCs and other computers, cell phones, and small handheld digital
devices. Services used to connect a
client computer to the Internet include email, electronic discussion groups,
chatting and instant messaging, Telnet, File Transfer Protocol (FTP), and the
Web. One or more software programs
implement each of these services. Voice
transmission and corporate networking and virtual private networks are other
platforms used by the Internet.
The Web is the most used Internet service with universally
accepted standards for storing, retrieving, formatting, and displaying
information using a client/server architecture.
A Web site is a collection of Web pages linked to a home page. Hypertext Markup Language (HTML) is a page
description language that describes how data should be presented in the form of
Web pages. Hypertext Transfer Protocol
(HTTP) is the communications standard used to transfer pages on the Web that
defines how messages are formatted and transmitted. A uniform resource locator (URL) tells the
browser software exactly where to look for a specific address on the Internet. A Web server is software that locates the Web
pages requested by a user on the computer where they are stored and delivers
them to the user’s computer.
Search engines are used to find useful
information on the Web nearly instantly.
The top three are Google, Yahoo, and Bing. In addition to search engines, shopping bots
are used to search for and find information.
They use intelligent agent software for searching the Internet for
shopping information.
Web 2.0 is a second-generation interactive
Internet-based service that allows people to collaborate, share information,
and create new services and content online.
It has four defining features, which include interactivity, real-time
user control, social participation (sharing), and user-generated content. Technologies and services behind these
features are cloud computing, software mashups and widgets, blogs, RSS, wikis,
and social networks. Web 3.0 is a future
version of the Web where all digital information is woven together with intelligent
search capabilities. This is also known
as the Semantic Web.
Cell phones, laptops, and small handheld
devices have evolved into portable computing platforms. In the United States the major computing
standard for digital cellular service is the Code Division Multiple Access
(CDMA). 3G and 4G are cellular networks
that allow high-speed, high-bandwidth, digital packet-switched transmission. Standards for wireless computer networks,
such as Bluetooth and Wi-Fi, allow computer users to have access to the
Internet without being connected with a wire or cable.
In addition to the wireless systems, radio
frequency identification systems and wireless sensor networks are having a
major impact. Radio frequency
identification (RFID) systems allow for tracking the movement of goods by using
tiny tags with embedded microchips containing data about an item and its
location to transmit radio signals over a short distance for processing. Wireless sensor networks (WSNs) are networks
of interconnected wireless devices that are embedded into the physical
environment to provide measurements of many points over large spaces.
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