chapter 6

Chapter 6

Network

*What is a Computer Network?

Computer Network: a system that connects computers and other devices (e.g. printers, smart phones) via communications media so that data can be transmitted among them 

In a computer network, connected computers:

v  Work together

v  Are interdependent

v  Exchange data  with each other

Bandwidth: the transmission capacity of a network. It is stated in bits per second (bps)

 Broadband: Network transmission capacities ranging from approximately 1 million bps (megabits/second) up to several terabits / second

Types of Computer Networks

v   Local Area Networks (LAN)

connects two or more devices in a limited geographical region(usually within the same building) so that every device on the network can communicate with every other device.

Trade-offs between:

Ø   Speed

Ø    Distance

Ø    Cost

§  Every device in the LAN has a network interface card (NIC)

§   NIC allows the device to physically connects to the LAN’s 

   communication medium

§   Network Server : contains various software (operating system)

 and data for the network

v  Wide Area Networks (WAN)

§     covers a large geographical area and have large capacity

§     Provided by telecommunication companies

§     WANs also contain routers

Router: a communication processor that routes messages from LAN to the Internet , across several connected LANs

v  Enterprise Networks

§  A network, encompassing an organization, composed of interconnected multiple LANs and WANs

§  Backbone Network:

high-speed central network to which multiple smeller networks connect.

*Network Fundamentals:

Networks transmit information with two types of signals:

·         Analog Signals:

Continuous waves that transmit information by altering the

 characteristics of the waves. Have two parameters : amplitude (higher the wave) and

  frequency (more closely packed).

·         Digital Signals

Discrete pulses that are either ON or OFF , representing a series of bits (0s and 1s)

ü  Modem (modulator-demodulator)

Converts digital signals to analog signals and vice versa

D → A  = Modulation

A → D  = Demodulation  

ü  Communication Media and Channels

Pathways for communicating data from one location to another

1.      Wire line Media  (Cable)

v  Twisted-Pair Wire

v  Coaxial Cable

v  Fiber-optic Cable

2.      Wireless Media    (Broadcast)

v  Microwave

v  Satellite

v  Radio

v  Infrared

ü  Transmission Technologies:

Digital Subscriber Line (DSL)

A technology that provides high-speed transmission of digital data over existing

copper telephone lines

§  OmantTel ADSL offers bandwidth up to 40 Mbps

Asynchronous Transfer Mode (ATM)

§  Can transmit up to 2.5 Gbps

§  Requires fiber-optic cables

§  More expensive than DSL

ü  Network Protocol

Set of rules and procedures that govern transmission across a network

Ethernet

§  A common LAN protocol

Transmission Control Protocol / Internet Protocol (TCP/IP)

§  The Protocol of the Internet

Packet Switching

Technology that breaks blocks of text into small, fixed bundles of data and routes them in the most economical way through any available communication channel

ü  Types of Network Processing

Distributed Processing

Divides processing work among two or more computers

Client-Server Computing

Links two or more computers in an arrangement in which some

machines, called Servers, provide computing services of users PCs, called Clients.

Peer-to-peer (P2P) processing

A type of client-server distributed processing where each computer acts as both client and a server.

*The Internet and the World Wide Web

·         The Internet  (“the Net”): Grew out an experimental project of the Advanced Research Project Agency (ARPA) of USA DoD in 1969 [ARPAnet)

§  Intranet

§  Extranet

·         Internet Service Provider (ISP):

A telecommunication company that offers Internet connections for a fee   

ISPs connect to one another through NAPs

·         Addresses on the Internet

Internet Protocol Address (IP) Address) : An assigned address that distinguishes each computer on the Internet from all other computers 135.62.128.91

·         The Internet Corporation for Assigned Names (ICANN)

Responsible for coordinating IP addresses throughout the world

ICANN accredits certain companies called registrars to register names (called Domain Names) that are equivalent to the IP address.  

*Network Applications:

Discovery: the Internet allows users to browse and search data sources, in all topic areas, on the Web.

Search engines:  computer programs that search for specific information by keywords and report the results.

*Other Interesting Search Engines:

FilesTube :  http://www.filestube.com/

Search and download files from file sharing and upload sites

Burrp :  http://www.Burrp.com/

Urban lifestyle guide will help you find a Thai restaurant in New York or a night spot in Mumbai

Gnosh:    http://www.gnosh.org/

A search tool that lets you search large media sites as well as social search engines

*Metasearch Engines:

searches several engines at once and integrate the findings of  the various search engines to answer queries posted by users.

*Portals:

Portal: a Web-based, personalized gateway to information and knowledge that provides relevant information from different IS systems and the Internet using advanced search and indexing techniques.

Four types of portals:

1.  Commercial (public) portals: offer content for diverse communities and are the most popular portals on the Internet

2. Affinity portals: offer a single point of entry to an entire community of interest, such as a hoppy group or political party

3. Corporate/ Enterprise portals: offer a personalized single point of access to information located within the organization

4. Industrywide portals: offer a single point of entry to information for an entire industry

Offers information about:

-          Professional drivers

-          Owner/operators

-          Trucking companies

-          Trucking jobs

-          Drivers (virtual) round table

*Communication:

Ø  Electronic mail (e-mail): transmission of electronic messages over the Internet the largest-volume application running on the Internet .

90% of companies conduct business transactions via e-mail

Ø  Web-based call centers (customer call center): are services that provide effective personalize customer contact as an important part of Web based customer support

Ø  Electronic chat room: a virtual meeting place where groups of regulars come to “gab”/ E-Chitchat

Ø  Voice Communication:  

Internet Telephony/ Voice-over Internet Protocol (VoIP) : digitizes your analog voice signals, sections them into packets, and sends them over the Internet

Ø  Unified Communications: simplifies and integrates all forms of communications , voice mail, fax, chat, e-mail, instant messaging, short message service, presence (location) services, and videoconferencing – on a common hardware and software platform.

*Collaboration:  refers to efforts of two or more entities (individuals, teams, groups, or organizations) who work together to accomplish certain tasks.

o   Work group:  refers specifically to two or more individuals who act together to perform some task.

o   Virtual group (team) is when group members are in different locations.

Crowdsourcing

§  Synchronous collaboration 

§  Asynchronous collaboration

o   Virtual collaboration: the use of digital technologies that enable organizations or individuals to collaboratively plan, design, develop, manage and research products, services and innovative applications.

o   Workflow technologies: facilitate the movement of information as it flows through the sequence of steps that make up an organization’s work procedures. Includes workflow management and workflow systems.

o   Groupware: software products that support groups of people who share a common task or goal and who collaborate to accomplish it.

o   Teleconferencing: the use of electronic communication that allows two or more people at different locations to hold a simultaneous conference.

o   Videoconference: is when participants in one location can see participants at other locations and share data, voice, pictures, graphics and animation by electronic means

o   Web conferencing: videoconferencing conducted over the Internet.

o   Real-time collaboration tools: support synchronous communication of graphical and text-based information i.e. computer-based whiteboards.

*Telepresence Systems:

The latest version of videoconferencing enable participants to  seamlessly share data, voice, images, graphics, video, and animation electronically.

*E-Learning and Distance Learning:  learning supported by the Web

§  Benefits:

ü  Students have the flexibility of learning from any place at any time at their own pace.

ü  Online materials deliver high-quality, current content.

ü  Training costs can be reduced.

§  Drawbacks:

ü  Instructors may need training to be able to teach electronically

ü  Students must be computer literate

ü  There are issues with assessing students’ work

*Telecommuting:

allows workers to work anytime and anyplace

§  Benefits :

v  For Employees:

ü  Reduced stress, improved family life

ü  Employment opportunities for single parents and persons with disabilities

v  For Employers:

ü  Increased productivity

ü  Ability to retain skilled employees

§  Drawbacks :

v  For Employees:

ü  Feelings of isolation

ü  No workplace visibility

ü  Potential for slower promotions

v  For Employers:

ü  Difficulties in supervising work

ü  Potential information security problems

ü  Additional training costs