AS Level ICT - Topic 8 Networks

Basic Elements of an ICT Network

Communication Devices -> Pieces of hardware which are required to turn stand-alone computers into networked computers

Network Interface Card (NIC) -> Need to have one of these before a computer can be connected to a network -> They are cards which have circuitry along with a socket and their purpose is to convert data from the form in which it is stored into a form which can be transmitted through the network media -> It prepares data for sending over the network, it sends the data and it controls the flow of data from the computer terminal to the transmission medium

Hub - Simple device which is used to join computers in a network so that they are able to share files and an Internet connection

Switches (network switches) - Used to join multiple computers together in a network and they contain more intelligence than hubs as they are able to inspect packets of data so that they are forwarded appropriately -> This reduces quantity of data on network which therefore speeds up the network

Routers -> Hardware devices which join several wired or wireless networks together

Networking Software -> Networks need software to tell connected devices how to communicate with each other

- Network Operating Systems Software -> Examples include UNIX, Linux and Novell Netware

 - Network Management Software -> Helps with tasks like making sure that all the computers have up-to-date software with the latest security patches and keeping all application software up-to-date -> It helps you look after every computer to keep the network running

Data Transfer Media-> Material which data travels through from one computer to another within a network

- Metal Wires -> Offer high transmission speed but they do need to be installed and this can be expensive and there are three types (unshielded twisted pair, shielded twisted pair and non-metal cables) -> Unshielded twisted pair have thin wires which are twisted to help cancel out interference, for easier installation but only suitable for small networks -> Shielded twisted pair have wires that are twisted and they have copper braiding which protects the data from outside interference but they are more expensive but greater transmission speeds -> With non-metal cables light pulses are used to carry data because light travels faster than electricity

Fibre Optic Cable -> Data being passed is encoded as pulses of light through a very thing glass fibre and lots of fibres are utilised to carry the data to and from the network -> Advantages: Data travels much faster, lots of data can travel through a very small cable and they don't suffer from interference -> Disadvantages: Only one and that is the cost

No Cables at all -> Wireless communication and the data transfer medium is the air

Wireless -> Allow people to connect to the Internet or to a LAN wirelessly which means that they can work anywhere -> Places where you can access the Internet using WiFi are called hot spots -> How WiFi Works: Router is connected to the Internet by a high-speed broadband connection, then the router receives data from the Internet and it transmits the data as a radio signal using an antenna and finally, the computer's wireless adapter picks up the signal and turns the radio signal into data that the computer can understand (when sending data this all happens in reverse -> Advantages: Freedom of working anywhere, global set of standards, enables inexpensive LANs to be set up without cables etc. -> Disadvantages: Power consumption is high, health problems, security problems, limited range and interference

Network Standards and Procedures

- Standards are vital as one device could be sending data to another device in a form which the other device cannot understand if they weren't in place

 - Without proper procedures -> Security compromised, slow, fall foul of legislation, lose work, inconvenient and annoying actions and actions which would cost the company time

Characteristics of Networks and Stand-alone Computers

- Stand-alone -> Computer used on its own without any connection to other computers and if data needs to be passed to another department, it needs to be printed out on paper or copied onto disk before being transferred by someone to someone else for entry into their computer system

 - Network -> Group of computers connected together with cables

Advantages of Stand-alone Environment - Cheaper hardware and software, less IT knowledge needed, fewer problems with viruses and not as hardware dependent

Disadvantages of Using Stand-alone Computers - Transfer of files between computers, hard to keep data up-to-date, harder to install software, harder to update software and backups need to be kept by each user

Advantages of Networks - Ability to share files, hardware and software, lower software costs, improved security, easier to implement acceptable use policies, easier to back up files, improved communication and central maintenance and support

Disadvantages of Networks - Technical knowledge needed, lack of access when file server fails and they are very expensive (equipment and training required)

ICT Networks for Different Geographical Scales and Uses

LAN stands for Local Area Network and WAN stands for Wide Area Network

 - LANs are confined to one building or site and WANs are distributed over multiple sites

 - Features of LANs include -> Hardware and communications equipment is contained in one building or site, ownership of the communications equipment

 - Features of WANs include -> Hardware is spread over a wide geographical area and third party telecommunications equipment is used (rent)

Differences Between Internet and the World Wide Web

- Internet -> Internet is a huge group of networks joined together and each of these netowrks consist of smaller networks

 - WWW -> Means of accessing information contained on the Internet and it is an information-sharing model which is built on top of Internet and it uses HTTP to transmit info and it uses browser software to gain access to documents called webpages

Using the Internet you can use e-mail facilities, instant messaging, usenet news groups, FTP and P2P

Intranets

- Private network using the same technology used by the Internet for sending messages around the network -> Main use is to share organisational info and resources and only employees are able to use it

Extranets

- Customers, suppliers and other partners can access information but general public CANNOT

 - Data needs to be sent using third parties for the communication lines

 - If Internet is used for sending of data in an extranet there has to be security measures; gateways; firewalls; encryption; and user authentication

The Internet

Benefits and Developments -> Methods of cheap communication, video, radio stations, send and receive files, run / download educational games and programs, research, etc.

Disadvantages -> Inappropriate material, 'friendships' with strangers, cyberbullying, advertising pressures, health problems, instrusion of privacy, gambling addiction, incorrect and inaccurate information

Communications -> Instant messaging, webcam services, cheap phone calls, chat rooms and text messaging

E-mail Services

An e-mail is an electronic message sent from one communication device to another

Search -> Allows you to find an e-mail using keywords in the title or you can search for all the e-mails from or to a certain e-mail address

Reply -> Allows you to read an e-mail and then write the reply without having to enter the e-mail address

Forward -> You can forward an e-mail to people who you think should see it e.g. an e-mail sent to you by your boss could be forwarded to everyone who works with you in a team

Address Book -> Instead of having to type in the address you just have to click on the address(es) in the address book

Groups -> Lists of people and their e-mail addresses and they are used when a copy of an e-mail needs to be sent to all those people in that specific group and this saves time

File attachments -> You can attach files to e-mails never mind how many

Voice Mailboxes -> Voice messages are sent and received and the user is informed if they have a message

Accessing Information -> Access huge amounts of information like dictionaries and encyclopaedias via Internet

Advantages of E-mail - Virtually instantaneous, no need for familiarity of a letter, easily attach a copy of sender's message with your reply, virtually free to send, accessed using variety of devices and more environmentally friendly

Disadvantages of E-mail - Not everyone has e-mail, may make users more casual, junk mail, worries about security aspects, system relies on people checking e-mail regularly, viruses

FTP (File Transfer Protocol)

- Method for exchanging files over the Internet and FTP transfers files in a similar way to the way webpages are transferred from the file server to the user's web browser when the user is viewing information using the Internet -> FTP transmits any type of file by a process which collects data into packages -> Package of data is sent and when received, the receiving system checks the package to make sure that no errors have been introduced during transmission -> Then a message is sent back to the sender system to let it know that the package is OK and that it is ready to receive the next package of data

Newsgroups

- Place where data is stored in the form of messages from different users at different locations

 - Usually a discussion group where people are able to post messages or replies to messages on a whole variety of topics

Chat Rooms

- Allow users to conduct real-time on-line discussions with others

 - Some offer more than just text, as they can offer audio and video communication

On-line Shopping

- Lots of people do this even if it is for a few things (more detail in Topic 6a)

Accessing Information Using On-line Databases

- Accessing an on-line database when searching for a holiday or flight etc.

 - On-line databases are used by companies to store the details of the services or stock

Search Engine Selection

- Way of finding information on the Internet

 - It is an Internet tool which will search for Internet sites containing words which you designate as a search term and then it gives you results in the form of links to the sites which have your term(s)

 - Each search engine looks at different databases and they all have different levels of sophistication