Networks A network is two or more

computers & devices that are connected via communication devices and transmission media allowing computers to share resources

Standalone device, computer not connected.

Networks

NetworksFor successful communications you need:• Sending device, eg. computer, mobile phone,

GPS receivers• Communications device, eg. broadband router,

dial up modem• Communication channel or transmission media,

eg. phone line, optic fibre, ADSL2• Communications device to receive, eg.

computer, etc.

Networks: Advantages1. Facilitating communications

• Enabling easy communicating, email, facebook, instant messaging, chat rooms, video conferencing, etc.

2. Sharing hardware• Networked computers can access peripheral devices, eg.

printers, photocopiers, etc. leading to lower costs than each device requiring a printer

3. Sharing data and information• Any authorised computer can access and store data &

information stored on other computers, servers, etc.4. Sharing software

• Users access networked software based on a site licence; this costs less than buying individual copies of s/ware.

5. Transferring funds• Networks enable EFT; transfer money, deposit salaries,

pay bills online.

Networks: Disdvantages

1. User dependence• When network is down users are not able to access

devices, share data, share software or undertake transfers, etc.

2. Management of the network• Networks require work to set up and maintain• Require skilled network staff, manager and support

personnel

LANs – local Area Network

LANs – local Area Network

• Group of computers connected by a neighbouring geographic area

• Each computer or device on network is a node

• Geographically limited, usually to one site, 5 kms

• Usually cabled with CAT 5, (UTP), or wireless lan, WLAN.

• Network operating system, (NOS) is system software that organises, controls & coordinates activities on LAN.

LANs – local Area Network• NOS controls attached computer systems &

peripheral devices• NOS performs these tasks

• Administration, eg. adding, deleting users, backup• File management, locating & transferring files• Printer management• Security, restricting access to network resources• 3 providers of NOS, Microsoft, Novell and Apple

Peer-to-Peer (P2P) networks

Peer-to-Peer (P2P) networks

- Simple inexpensive network where each node shares hardware & data with all other computers on network

- No server, so costs are low and installation is simple- All computers and users have equal authority and

rights- Little protection of one workstation against another-Used at home or in small organisations with trusted users-Allows sharing of files, internet connection, printer-

Client-Server networks

Client-Server networks- One computer program (the ‘client’) asks another

computer program (the ‘server’ or host computer) to provide a service, such as looking up and providing data, delivering email, sending web pages, bank balances etc.; eg. server at school

- Server computer has more storage capacity and power than clients• Some different types of servers:• file servers, store files for use on client

computers • application servers, store applications to

enable clients access

Client-Server networks• print servers, accepts print jobs over the network

faster than a printer; workstation gets on with other tasks whilst printing is done

• Database server; hold d/bases and allows them to be used by many users

• web servers, connected to internet and serve webpages to viewers

- Advantages/disadvantages:- Costs significantly higher than peer-to-peer & ongoing

technical support- Advantages are economies of scale of sharing

resources, backup and security against viruses, etc.

Wide area networks, the internet• Wide Area Network (WAN) – broad geographic coverage

(e.g. state-wide, country-wide, international)• Communications carried by a medium owned by someone

who is not part of the organisation whose data is being transmitted

• Transmission media include microwave, fibre-optic, telephone lines & satellite.

• WANs include:• Statewide network• National area network• World wide network, eg. internet

Internet-Peer to Peer (P2P) networks

- Users must enable their computer to be accessed by others over the internet. This allows copying of files from one hard drive to another via the internet.

- P2P, enabling users with same networking software to connect to each other’s hard disks and exchange files directly

- Internet music sharing networks such as BitTorrent, Limewire & Kazza are software applications that support peer-to-peer

- This style of network can expose your computer to possible security violations.

Internet-Peer to Peer (P2P) networks

- Once connected you have access to their hard disks- Examples, Kazaa and Limewire- Exposure to possible security violations, eg. viruses

and trojans