Networks

Mr Arthur

Aims of Lesson 1

1. Introduce networks

2. LANs

3. WANS

4. Transmission Media

5. Client Server and Peer-to-peer networks

Stand Alone/Networked

A Stand Alone computer system is a computer that is not connected to any other

A network is a linked set of computer systems that are capable of sharing programs, data and sending messages

Local Area Networks

A LAN is a network of computers connected over a small geographical area, usually inside the 1 building

Examples School LAN Network in a library

Uses Sharing resources Sharing peripherals Email

Transmission Media Copper Wire, Fibre Optic and Wireless

Wide Area Networks

A WAN is a network of computers over a large geographical area, such as across a country or the world.

Examples The Internet Companies like the BBC communicating across the world

Uses video-conferencing, use of e-mail, live chat Sharing Information - access to databases, E-commerce and entertainment

Transmission Media Fibre Optic, Microwave transmission and Satellite

Client Server Network A client-server network is where all resources are stored

centrally on the server and are assessed by the client stations

Advantages Increased security as each user needs to log in Different levels of access are available Users can work on the same document at the same time Flexible uses of station, you can log on to a number of clients

and access your files Backup copies are completed centrally

Disadvantages If the file server is down there is no access to data More expensive as you need to buy a server and server

software

Peer to Peer Network

A peer-to-peer network is where each station has its own local storage device.

Advantages Easier to setup operating systems on stations in a peer-

to-peer Cheaper as no server is required

Disadvantages No central file storage – users must log in to the same

station to access files Users must backup their own data Peer-to-peer is less secure as users may not be required

to log in

Aims of Lesson 2

Last Lesson Introduce networks LANs WANS Transmission Media Client Server and

Peer-to-peer networks

Today’s Lesson

1. Network Topologies

2. Network Interface Cards

3. Hotspots

Star Topology

All peripheral nodes are connected to a central node

If a peripheral node fails it has no effect on the network

If the central node fails the whole network is “down” Advantage = Easy to add new

stations Disadvantage = Central node may

get congested with network traffic

Ring Topology

Signals are sent around the network from node to node

If a node is faulty, then there must be a method of bypassing the failed node

If a communications channel fails, the network fails

Bus Topology

The bus topology has each node connected to a main communication channel (The Bus)

If one node is faulty this has no effect on the rest of the network

If the bus is faulty, the whole network is “down” Advantage = Easy to add new stations Disadvantage = Each node may have to

compete with each other in order to transmit and receive data

Mesh Topology

A mesh topology has multiple direct connections between each node

The internet is an example of a Mesh network Advantage = A node failure

has no effect on the rest of the network

Disadvantage = Expensive to set up with a lot of cabling

Network Quiz

1. Give 3 functions of a LAN

2. Give 3 transmission media you would associate with a LAN

3. Describe a client server network (2)

4. Give 2 advantages of a client server over a peer to peer network

5. Describe a peer to peer network

Aims of Lesson 3

Last Lesson Introduce networks LANs WANS Transmission Media Client Server and

Peer-to-peer networks Network Topologies

Today’s Lesson

1. Network Interface Cards

2. Hotspots

3. Router

4. Hubs

Network Interface Cards

Network Interface Cards = a small printed circuit board inside the computer system allowing it to communicate with the network.

The NIC provides the computer with a unique Media Access Control (MAC) address made up of 6 bytes

Hotspots

An area where network signals may be received

Usually located in built up areas

May be deliberate hotspots in a University or may be accidentally created Warchalking Wardriving

Router A router is a device

which links 2 or more networks

The router takes packets of data and decides which route through the network the packet should take

HUBs

A hub is a device with multiple ports which allows more than 1 device to share the same wire

The hub will also boost or amplify signals

Multi-port repeater

Switch

A switch operates like a smart hub

The switch separates the network into segments

More than one machine can speak at once and only the intended recipients receives the signal

Aims of Lesson 4

Last Lesson Introduce networks LANs WANS Transmission Media Client Server and Peer-to-

peer networks Network Topologies Network Interface Cards Hotspots Router Hubs

Today’s Lesson1. Mainframes/Super

computers2. Current network trends3. Technical reasons for

increasing number of networks

Mainframes and Supercomputers

Mainframes A large powerful computer

which can process a very large amount of data at a high speed

May be connected to hundreds of dumb terminals

Multi-programming Multi-tasking Multi-processors

Supercomputers More powerful than a

Mainframe Supercomputers are used

for intensive mathematical calculations like weather forecasting, aerospace engineering

Current Network Trends

Higher Bandwidth Increasing amount of data carried

along communications channel Virgin Media advertising 20Mbps!!! There will be a limit however,

depending on the distance from subscriber and the telephone exchange

Wireless Functions WiFi, Bluetooth, Zigbee

Technical Reasons for Increasing Number of Networks

Advances in computer hardware Faster, Multiple processors Cheaper, higher capacity RAM chips Increasing Backing storage capacities Increasing data transfer rates

Improved Network software Browsers = improved functionality using

plug-ins, allowing streamed video, animated graphics to be displayed

Operating Systems designed with networking functions built in

Final Network LessonLast Lesson Introduce networks LANs WANS Transmission Media Client Server and Peer-to-peer

networks Network Topologies Network Interface Cards Hotspots Router Hubs Mainframes/Super computers Current network trends Technical reasons for

increasing number of networks

Today’s Lesson File, Print and Web servers Legislation

Computer Misuse Act Copyright Designs and

patents act Data Protection Act

File/Print/Web Servers

File Server A file server provides central disk

storage for user’s programs and data on the network

The file server will run 24 hours a day and must have a fast processor, lots of RAM and much larger hard disk capacity

Controls security on the network Backed up using a Digital Audio

Tape (DAT) Print Server

A print server will allow multiple clients share the same printer

The print server will use a spooler program and the printer will probably have a buffer as well

Web server A web server is a computer

that provides WWW services to a network

You have the benefit of “always on” fast access to pages

Every computer that host a website must have a web server program

Misuse of Networks

Copyright Designs and Patents Act This makes it illegal to copy music,

programs, movies etc without the permission of the owner

Computer Misuse Makes it illegal to hack or spread viruses

Data Protection Act Controls the storage of personal

information