Networks
What is a Computer Network ?
Computer Network : is a system that connects computers and other devices (e.g. printers) via communications media so that data and information can be transmitted among them.
◆Work together.
◇Are interdependent.
◆Exchange data with each other.
Bandwidth : refers to the transmission capacity of network, it is stated in bits per second.
Broadband : refers to network transmission capacities ranging from approximately 1 million bits per second (megabits/s) to as much as 20 megabits/s with fiber-to-the-home.
Broadband connections such as⇨digital subscriber line (DSL) and cable in homes and dorms.
Types of computer networks :
⇨personal area networks(PANs)
⇨Local area networks(LANs)
⇨Metropolitan area networks(MANs)
⇨Wide area networks(WANs)
⇨Internet.
Local Area Network (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. Most LAN today use Ethernet.
Every device in the LAN has a network interface card (NIC) allows the device to physically connect to the LAN's communications medium. This medium is typically unshielded twisted-pair wire (UTP).
LANs have a file server or network server.
Network server : Contains various software (operating system) and data for the network.
Wide Area Network (WAN) : Are networks, that cover large geographic areas. WANs typically connect multiple LANs.
WANs generally are provided by common carriers such as telephone companies and international networks of global communications services providers. WANs have large capacity.
e.g. of WAN is Internet.
WANs contain routers.
Router : Is a communications processor that routes messages from LAN to the Internet, across several connected LANs, or across a wide area network such as the Internet.
Enterprise Networks : A network, encompassing an organization, composed of interconnected multiple LANs and WANs.
Backbone networks : Are high-speed central networks to which multiple smaller networks (such as LANs and smaller WANs) connect. Tle LANs are called embedded LANs because they connect to the backbone WAN.
Network Fundamentals :
Networks transmit information with two types of signals :
1) Analog Signals : Are continuous waves that transmit information by altering the characteristics of the waves. Analog signals have two parameters, amplitude (the higher the wave) and frequency (more closely packed).
2) Digital signals : Are discrete pulses that are either on or off, representing a series of bits (0s and 1s). This quality allows digital signals to convey information in a binary from that can be interpreted by computers.
Modem (modulator-demodulator) : Converts digital signals to analog signals⇨aprocess called modulation, and analog signals to digital signals⇨a process called demodulation.
There are three types of modems :
✔Dial-up modems.
Dial-up modems have transmission speeds of up to 56Kbps.
✔Cable modems.
Cable modems are that operate over coaxial cable⇨e.g.TV cable.
✔DSL modems.
DSL (digital subscriber line).modems operate on the same lines as voice telephones and dil-up modems.
Communication Media and channels :
Communication Media and channels : the pathways for communicating data from one location to another.
Two type of media :
cable (wireline media) : use physical wires or cable to transmit data and information.
Twisted-pair wire, and coaxial cable ➡made of copper.
Fiber-optic cable ➡ made of glass.
Discretion
|
Advantages
|
Disadvantages
| |
Twisted-Pair Wire
|
is the prevalent form of communications wiring, it used for almost all business telephone wiring. It consists of strands of copper wire twisted in pairs.
|
✔Inexpensive.
✔Widely available.
✔Easy to work with.
✔Unobtrusive.
|
✘Slow (low bandwidth).
✘Subject to interference.
✘Easily tapped (low security).
|
Coaxial Cable
|
consists of insulated copper wire, it commonly used to carry high-speed data traffic as well as television signals.
|
✔Higher bandwidth than twisted-pair.
✔Less susceptible to electromagnetic interference.
|
✘Relatively expensive and inflexible.
✘Easily tapped (low-to-medium security).
✘Somewhat difficult to work with.
|
Fiber Optic Cable
|
consist of thousands of very thin filaments of fibers that transmit information via light pulses generated by lasers. it surrounded by cladding, a coating that prevents the light from leaking out of the fiber.
|
✔Very high bandwidth.
✔Relatively inexpensive.
✔Difficult to tap (good security).
|
✘Difficult to work (difficult to splice).
|
broadcast (wireless media) : communications channels that use electromagnetic media (the "air waves") to transmit data (e.g. microwave, satellite, radio, and infrared).
********************************************************************
Transmission Technologies :
Transmission Technologies : a number of telecommunications technologies enable users to transmit high-volume data quickly and accurately over any type of network.
◆Digital Subscriber Line(DSL) ⇨provide high-speed transmission of digital data from homes and businesses over existing telephone lines.
⇨DSL systems must include modem.
⇨DSLs offer bandwidth from 128Kbps 3Mbps.
⇨DSL service available only within 18000 feet of provider central office.
◇Asynchronous Transfer Mode(ATM) ⇨networks allow users to access almost unlimited bandwidth on demand.
⇨ATM Provide support for data, video, and voice transmission on single communications line.
⇨ATM requires fiber-optic cable.
⇨can transmit up to 2.5 Gbps.
⇨More expensive than DSL.
◆synchronous Optical Network ⇨is an interface standard designed to carry large volumes of traffic over relatively long distances using fiber-optic line.
⇨SONET defines optical line rates(optical carrier(OC).
◇T-Carrier System⇨ is a digital transmission system that defines circuits that operate at different rates all of which are multiples of the basic 64Kbps used to transport a single voice call.
Network Protocols :
☆Ethernet⇨a common LAN protocol.
☆Transmission Control Protocol/Internet protocol(TCP/IP) ⇨is the protocol of the Internet.
⇨Transmission Control Protocol(TCP) performs three basic function: (1) It manages the movement of packets between computers by establishing a connection between the computers. (2)It sequences the transfer of packets. (3)It acknowledges the packets that have been transmitted.
⇨Interent protocol(IP): is responsible for disassembling, delivering, and reassembling the data during transmission.
● 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.
The (TCP/IP) function in four layers :
- Application.⇨hypertext transfer protocol(HTTP): defines how messages are formulated and how they are interpreted by their receivers.
- Transport.
- Internet.
- Network interface.
Distributed processing: Network architecture that divides processing work between two or more computers, linked together in a network.
A common type of distributed processing is client/server processing. A special type of client/server processing is peer-to-peer processing.
✳Client/Server Computing⇨links two or more computers in an arrangement in which some machines, called servers, provide computing services for user PCs called clients.
Client/server computing leads to the ideas of " fat" clients and "thin" clients. Fat clients have large storage and processing power and therefore can run local programs such as Microsoft Office application. In contrast thin clients my have no local storage and limited processing power.
Peer-to-Peer Processing⇨A type of client/server distributed processing that allows two or more computers to pool their recourse's, making each computer both a client and a server.
type of peer-to-peer processing:
- Accesses unused CPU power among networked computers⇨e.g. SETI@home.
- Person-to-person collaboration⇨e.g. Microsoft SharePoint Workspace.
- Advanced search and file sharing⇨e.g. BitTorrent.
The Internet (the Net) : The massive network that connects computer networks of businesses, organizations, government agencies, and schools around the world, quickly, seamlessly, and inexpensively. For the Internet the backbone is a fiber-optic network, that is operated by large telecommunications companies.
The Internet grew out an experimental project of the Advanced Research Project Agency (ARPA) of the U.S Department of Defence in 1966 (ARPAnet).
Intranet :is a network that uses Internet protocols so that users can take advantage of familiar applications and work habits. It support discovery, communication, and collaboration inside organization.
Extranet :is a network that connects parts of the intranets of different organizations. It enables business partners to communicate securely over the Internet using virtual private networks.
Accessing the Internet :
★Connecting via an Online Service.
⇨Internet Service Provider(ISP)⇨Is telecommunication company that offers Internet connections for a fee. To find a local ISP access www.thelist.com .
ISPs connect to one another through NAPs.
⇨Network Access Point(NAP)⇨Computers that act as exchange points for Internet traffic and determine how traffic is routed.
★Connecting via Other Means.
There have been several attempts to make access to the Internet cheaper, faster, and easier.e.g. terminals known as Internet kiosks have been located in public places like libraries and airports. Accessing the Internet from smartphones and ipads is common, and fiber-to-the-home(FTTH) is growing rapidly , which involve connecting fiber-optic cable directly to individual homes.
★Addresses on the Internet.
⇨Internet Protocol (IP) address⇨An assigned address that distinguishes each computer on the Internet from all other computers. IP address consists of numbers in 4 parts separated by dots. e.g. 135.62.128.91.
IP address must be unique, The Internet Corporation for Assigned Names(ICANN)(www.icann.com) coordinate these unique address throughout the world.
ICANN accredits certain companies called registrars to register these names,which are derived from system called the domain name system (DNS).
⇨Domain Name System (DNS)⇨ The system administered by the ICANN that assigns name to each site on the Internet.
⇨Domain Name⇨ the name assigned to an Internet site, consisting of multiple parts, separated by dots which are translated from right to left.
e.g domain name :
com commercial sites
edu educational sites
mil military government sites
gov civilian government sites
org organization
The future of the Internet :
consumer demand for content delivered over the Internet is increasing 60% per year. As result Internet 2 has been developed by more than 200 U.S universities in collaboration with industry and government.
consumer demand for content delivered over the Internet is increasing 60% per year. As result Internet 2 has been developed by more than 200 U.S universities in collaboration with industry and government.
Internet 2 : A new, faster telecommunications network that deploys advanced network applications such as remote medical diagnosis, digital libraries, distance education, online simulation, and virtual laboratories.
The world wide web :
The World Wide Web( the web, WWW, or W3) : A system of universally accepted standards for storing, retrieving, formatting, and displaying information via a client/server architecture, it uses the transport functions of the Internet.
✳Website⇨ collectively, all of the web pages of a particular company or individual .
✳Uniform Resource Locator(URL)⇨ the set of letters that identifies the address of a specific resource on the web.
✳Browsers⇨ software applications through which users primarily access the web.
Network Applications :
Discovery :
Discovery: the Internet allows users to borrows and search data sources in all topic areas on the web.
Search Engines and Metasearch Engines
⇨Search engine ⇨is a computer program that searches for specific information by key words and then reports the results.
e.g. of search engins :
➡Google (www.google.com)
➡Yahoo! (www.yahoo.com)
➡Microsoft Network (now called Bing, www.msn.com)
➡FilesTube (www.filestube.com)
⇨Metasearch engines⇨searches several engines at once and integrate the findings of the various search engines to answer queries posted by users.
e.g. of metasearch engines :
➡Surf-wax (www.surfwax.com)
➡Metacrawler (www.metacrawler.com)
➡Mamma (www.mamma.com)
➡KartOO (www.kartoo.com)
publication of Material in Foreign Languages .
Information's available in different languages, in order to access this information's, people can use an automatic translation of web pages.
e.g. of major translation products are :
↘Altavista (http://babelfish.altavista.com)
↖Google (www.google.com/language_tools)
↘Trados (www.trados.com)
companies should care about providing their web sites in multiple languages, because of nature of the business environment. Companies increasingly are looking outside their home markets to grow revenues and attract new customers. To reach 80% of the world's Internet users, a web site need to support a minimum of 10 languages.
✔ http://oman-qaboos.net/ supports 14 different languages.
Portals.
⇨Portal⇨is a web-based personalized gateway to information and knowledge that provides relevant information from different IT systems and the Internet using advanced search and indexing techniques.
Four types of portals :
Commercial (public) Portals⇨a website that offers fairly routine content for diverse audiences, offers customization only at the user interface. It is the most popular portals on the Internet.⇨e.g. Lycos(www.lycos.com) & Microsoft Network(www.msn.com).
Affinity Portals⇨offer a single point of entry to an entire community of affiliated interests such as hobby group or political party.⇨e.g (www.techweb.com) & (www.zdnet.com).
Corporate Portals⇨offer a personalized, single point of access through a web browser to critical business information located inside and outside an organization. Also known as enterprise portals, information portals and enterprise information portal.
Industrywide Portals⇨offer a single point of entry to information for an entire industry. ⇨e.g. TruckNet(www.truck.net)
➡it offer information about:
▧ Professional drivers.
▧ Owner/operators.
▧ Trucking companies
▧ Trucking jobs.
▧ Drivers(virtual) round table.
Communication :
Electronic Mail.
⇨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.
Web-Based Call Centers.
⇨Web-Based Call Centers (customer call center)⇨are services that provide effective personalize customer contact as an important part of web based customer support. It also known as customer care centers. e.g. if you need to contact a software vendor for technical support, you usually will communicate with the vendor's web-based call center, using email, a telephone conversation, or a simultaneous voice/web session.
Web based call center are located in foreign countries such as India.
Electronic Chat Room.
⇨Electronic Chat⇨an arrangement whereby participants exchange conversational messages in real time.
⇨Chat Room⇨ is a virtual meeting place where many people (in fact, anyone) come to "gap"/E-Chitchat. Chat programs allow you to send messages to people who are connected to the same channel of communication at the same time.
Two types of chat programs:
☆web-based chat program, which allows you to send messages to Internet users by visiting a web chat site⇨e.g. (http://messenger.yahoo.com).
☆an e-mail-based (text-only)program called Internet Relay Chat (IRC)
Voice Communication.
⇨Internet Technology/Voice-Over Internet Protocol(VOIP)⇨The use of the Internet as the transmission medium for telephone calls. That is, it digitizes your analog voice signals, sections them into packets, and sends them over the Internet.
VOIP can reduce monthly phone bill. However, packet switching can cause garbled communication, but this less of an problem than in the past, because VOIP software continues to improve.
e.g. ⇨ Skype & Vonage.
Unified Communications.
⇨Unified Communications(UC)⇨simplifies and integrates all forms of communicatios—voice, voice mail, fax, chat, e-mail, instant messaging, short message service, presence (location) services, and videoconferencing—on a common hardware and software platform.
UC unifies all forms of human and computer communications into a common user experience.
Collaboration:
Collaboration: refers to efforts by two or more entities—that is, individuals, teams, groups or organizations—who work together to accomplish certain tasks.
Work Group: refers specifically to two or more individuals who act together to perform some task.
Workflow: Is 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.
Virtual Group (team): is when group members are in different locations. Virtual groups conduct virtual meetings, that is, they meet electronically.
virtual collaboration (e-collaboration): the use of digital technologies that enable organizations or individuals to collaboratively plan, design, develop, manage, and research products, services, and innovative applications.
Type of collaborations :
Crowdsourcing refers to outsourcing a task to an undefined, generally large group of people in the form of an open call.
Synchronous collaboration meaning that all team members meet at the same time.
Asynchronous collaboration when team members can not meet at the same time. Members are located throughout the world, must collaborate asynchronously.
Groupware: software products that support groups of people who share common task or goal and who collaborate to accomplish it.
Major collaboration software products:
Microsoft SharePoint.
Provides shared content with version control. SharePoint supports document directories and has features that enable users to create and manage surveys, discussion forums, wikis,member blogs, member websites, and workflow. example of a company that has used SharePoint effectively is Continental Airlines.
Google Docs
Is free web-based word processor, spreadsheet, and presentation application. It enables users to create and edit documents online while collaborating with other users
IBM Lotus Quickr
product provides shared content with version control in the form of document directories with check-in and check-out features based on user privileges. Quickr provides online team space where members can share and collaborate by utilizing team calenders, discussion forums,blogs,wikis, and other collaboration tools for managing projects and other content. Compagine d'Enterprises(CFE) one of the largest construction companies has put the collaboration tools of Quickr to good use.
Jive
newest product, Clearspace, uses web collaboration and communication tools such as forums, wikis and blogs to allow people to share content with version management, via discussion rooms, calendars, and to-do lists.
Electronic Teleconferencing
⇨Teleconferencing⇨ is the use of electronic communication technology that enables two or more people at different locations to hold a simultaneous conference. The biggest disadvantages of conference calls is that they do not allow participants to communicate face to face.
participants at other locations and can share data and graphics by electronic means.The latest version of videoconferencing, called telepresence, enables participants to seamlessly share data, voice, pictures, graphics,and animation electronically.Web Conferencing: videoconferencing conducted over the Internet.Real-Time Collaboration Tools: support synchronous communication of graphical and text-based information e.g. computer-based whiteboards.⇨Teleconferencing⇨ is the use of electronic communication technology that enables two or more people at different locations to hold a simultaneous conference. The biggest disadvantages of conference calls is that they do not allow participants to communicate face to face.
E-Learning and Distance Learning :
E-learning: refers to learning supported by web, can be done inside traditional classrooms or in virtual classrooms.
e.g. Easy Learning by Oman Tel.
E-learning is a part of distance learning.
Distance learning (DL):refers to any learning situation in which teachers and students do not meet face-to-face.
✳Benifits of E-Learning :
✔Students have the flexibility, of learning from any place at any time at their own pace.
✔Online materials deliver high-quality, current content.
✔Training cost can be reduced.
✳Drowbacks of E-Learning:
✘Instructors may need training to be able to teach electronically.
✘Students must be computer literate.
✘There are issues with assessing student's work.
Virtual Universities :
Virtual Universities:are online universities in which students take classes from home or at an off-site location, via the Internet.
e.g of virtual universities : University of Phoneix (www.phoneix.edu) ,California Virtual Campus (www.cvc.edu), & University of Maryland (www.umuc.edu/gen/virtuniv.shtml).
Telecommuting :
Telecommuting/Teleworking :A work arrangement whereby employees work at home, at the customer's premises, in special workplaces, or while traveling, usually using computer linked to their place of employment.
In simple words, It allow workers to work at anytime and anyplace.
✳Benefits of Telecommuting :
For Employees:
✔Reduce stress, improved family life.
✔Employment opportunities for single parents and persons with disabilities.
For Employers:
✔increased productivity.
✔ Ability to retain skilled employees.
✳Drowbacks of Telecommuting :
For Employees:
✘Feeling of isolation.
✘No workplace visibility.
✘Potential for slower promotions.
For Employers:
✘Difficulties in supervising work.
✘Potential information security problems.
✘Additional training cost.