Networking

A group of computers linked together to share resources. Common types are Local Area Networks (LAN), Wide Area Networks (WAN) and intranets.

Local Area Network (LAN)

Is a high-speed data network that covers a relatively small geographic area. It typically connects workstations, personal computers, printers, servers, and other devices.

LANs offer computer users many advantages including:

shared access to peripheral devices and applications

file exchange between connected users

communication between users via electronic mail and other applications

Network Interface Card

Allows a computer to communicate within a network. Small circuit board fitted inside the computer system.

Desktop computers are most likely to be connected to a LAN. Although laptops now come with network interface cards.

How does it work?

The NIC provides the computer with a unique address, made up of 6 bytes.

Wireless Network Interface (WiFi)

Allows a computer to communicate within a network from any where in the immediate vicinity of a wireless base.

Wireless Hotspot

Area where wireless network signals may be received and computers can connect to the network.

• Universities

• Hotels

• Trains

LAN - Cabling Used

Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs.

Twisted-pair copper cable

Bandwidth

(10 Mbps (Ethernet) 100 Mbps (Fast Ethernet))

Co-axial Cable

Bandwidth

(ranges up to 1 Gbps)

Fibre Optic Cable

Transmits light rather than electronic signals eliminating the problem of electrical interference.

Optical Fibre is fibres of glass, usually about 120 micrometres in diameter, which are used to carry signals in the form of pulses of light over distances up to 50 km without the need for repeaters.

a. Transmission media

c. Geographical spread

d. Functions

b. Bandwidth

In looking at the four categories of networks we will compare them using the following four characteristics:

Refers to the type of cabling or wireless method used to transfer data.

Relates to the speed at which data can be transferred throughout the network.

Looks at the size of the area which the network covers.

Considers what tasks the network can carry out for the users.

1. LAN

2. WAN

3. Internet

4. Intranet

a. Transmission media

c. Geographical spread

d. Functions

b. Bandwidth

Fibre-optic cable, Unshielded twisted pair(UTP) cable, co-axial cable (as used in a tv aerial.)

This depends on the cabling and hardware used. UTP cable allows data transfer at 10 – 100 Mbps

Physical cabling is laid to connect the network. Usually one building, school, office, factory.

Peripheral sharing, electronic mail, data sharing.

http://fcit.usf.edu/network

1. LAN

2. WAN

3. Internet

4. Intranet

a. Transmission media

c. Geographical spread

d. Functions

b. Bandwidth

Telecommunications systems covering large areas.

Slower than LAN. Depends on the link used. Modem dial-up up to 56 Kbps. ADSL up to 9 Mbps, dedicated line up to 45 Mbps.

WANs can cover any size of area. They use telecommunications which covers most of the earth.

Electronic mail, data sharing, conferencing.

1. LAN

2. WAN

3. Internet

4. Intranet

a. Transmission media

c. Geographical spread

d. Functions

b. Bandwidth

Telecommunications systems covering large areas.

Same as WAN. Depends on the link used. Modem dial-up up to 56 Kbps. ADSL up to 9 Mbps, dedicated line up to 45 Mbps.

The Internet can cover any size of area. They use telecommunications which covers most of the earth.

Electronic mail, information sharing using WWW, File sharing using FTP.

An internet is a network of networks

1. LAN

2. WAN

3. Internet

4. Intranet

a. Transmission media

c. Geographical spread

d. Functions

b. Bandwidth

Telecommunications systems covering large areas.

Slower than LAN. Depends on the link used. Modem dial-up up to 56 Kbps. ADSL up to 9 Mbps, dedicated line up to 45 Mbps.

Intranet can cover any size of area using telecommunications links which cover most of the earth. West Dunbartonshire Council has its own intranet.

An intranet is like the internet but confined to one organisation.

Electronic mail, information sharing using WWW, File sharing using FTP.

Intranet

Usually owned and managed by a company, an intranet enables a company to share its resources with its employees without confidential information being made available to everyone with Internet access.

Company News (warnings about thieves!)

Suppler Addresses

News on advertising (TV, News Paper)

Email other stores

Network ManagerPerson in charge of the network. He or she will be responsible for all the computer systems attached to the company network.

• Control software installation and upgrades centrally.• Control firewall protection• Provide virus checking• Do daily back-ups• Provide technical support• Implementing Network security measures (usernames and passwords)

A very large network may have several network managers.

Wide Area Network (WAN)

A computer network that spans a relatively large geographical area. The Internet is the best-known example of a wide area network.

Use a range of connection methods:

• Satellite

• Optical Fibre

Communication on a WAN

Email

Use email on Wide Area Networks. Users can transfer files by attachments. (selling)

Newsgroups

Allows people with similar interests to discuss and ask questions.

Electronic Forum

Similar to newsgroups, user needs to join before they can read and send messages. (e.g scholar)

Access to information on a WAN

Information Service

• News

• Technical Information

• Other data (study)

Search Engines

A program that searches documents for specified keywords and returns a list of the documents where the keywords were found. Google, Ask Jeeves etc

Entertainment Services Available

Internet Radio

Live Video

Networked Games (allows user to participate in tournaments and competitions)

Tele-working

Working from home instead of travelling to work.

Users use communication technology to keep in touch with their employer.

Advantages for Employee

• Save on travel time and cost.

• Look after young family. Save in child care.

Disadvantages for Employee

• Feeling of isolation.

• Work more hours.

• Need computer system at home

Advantages for Employer

• Employers save money on office space

• Tele-workers often harder at home

• Save money on wages by employing people in other parts of the world.

Disadvantages for Employer

• Train works on communication software

• Buy the computer system

Video Conferencing

Allows people to communicate with each other using sound, video and share data such as text and graphics even though they are miles apart.

• Requires a high bandwidth connection (expensive). However, can be cheaper than flying to the country.

• Specialised equipment (webcam)

Mainframes and Networks

Terminal

Terminal

Terminal

Terminal

Mainframes

A large, powerful computer serving many connected terminals and usually used by large, complex organizations.

Terminal (“Dumb”)

A device that allows you to send commands to a computer somewhere else. At a minimum, this usually means a keyboard and a display screen an some simple circuitry. No processing power.

Thin Client Networks

Low specification systems running off a very high specification server, small application tasks, eg browsing the internet.

The topology of a network refers to the shape of the network, how the computers are physically connected together.

A node is any device which is attached to the network.

A channel is the way in which data is transferred from one node to another.

e.g. a computer, printer, server, router.

This could a cable or some form of wireless technology.

Four topologies are covered in the Higher Course.

node

channel

Investigate Topolgies

• What type of network uses this topology

• How many channels connect the nodes

• Is communication seen by only one node or all

• What will happen in a node failure

• What will happen in a channel failure

1. Bus

2. Star

3. Ring

4. Mesh

Used in LANS.

All nodes are connected to a single channel.

A communication from one node is seen by all the other nodes.

Each node will recognise and accept communications which are addressed to it.

or

nodechannel

1. Bus

2. Star

3. Ring

4. Mesh

Node Failure

Channel Failure

There is typically a mechanism to bypass a failed node so failure of one node will only affect that node. Rest of network will still function.

A channel failure will cause the whole network to fail.

ornodechannel

1. Bus

2. Star

3. Ring

4. Mesh

Used in LANS.

Each node has its own channel to the central node.

The whole network depends on the proper functioning of the central node.

Cabling cost is high because each node has its own channel but it is easy to extend the network.

nodechannel

1. Bus

2. Star

3. Ring

4. Mesh

Node Failure

Channel Failure

A failure of one node will only affect that node. Failure of the central node will disable the entire network.

A channel failure will only affect the outer node on that channel.

nodechannel

1. Bus

2. Star

3. Ring

4. Mesh

Used in LANS.

Channels and nodes form a ring.

Only one node can transmit at a time and data passes between nodes until it reaches its destination.The network has to be disrupted when a new node is added. Designing and extending the network is more difficult than with a star network.

nodechannel

1. Bus

2. Star

3. Ring

4. Mesh

Node Failure

Channel Failure

A channel failure will disable the entire network.

nodechannel

There is typically a mechanism to bypass a failed node so a failure of one node will only affect that node.

1. Bus

2. Star

3. Ring

4. Mesh

Used in WANS. e.g. telephone grid.

There are alternative channels between nodes.

Several nodes can transmit at a time and data can be redirected when some channels are busy.

The extra cabling makes this an expensive type of network to set up but it is very robust.

nodechannel

1. Bus

2. Star

3. Ring

4. Mesh

Node Failure

Channel Failure

The failure of one node will only affect that node.

A channel failure will have no effect as alternative channels are available. It may, however, slow down traffic on the network.

nodechannel

Network Operating Systems

10 – 20 Years ago networks and their operating systems where:• Very expensive• Difficult to configure

Today’s NOS• Modern OS have network capability built into them• Very easy to configure and inexpensive

TCP/IP A common software standard for connecting a network, nowadays very easy and inexpensive.

Internet Protocol (IP)A packet-based protocol for delivering data across networks.

Features of NOS

• Multi User Access

• Privacy and Security of network

• File and Print Services

• Data Sharing

Protocol

An agreed upon format for transmitting data between two devices. Determines:

• error checking used

• data compression method

HTTP - Hyper Text Transfer Protocol

TCP-Transmission Control Protocol

• Ensure that packets travel safely on an internet.

• Keeps track of package

• Detects errors

Packet

Unit of data formatted for transmission on a network. Data is broken up into packets for sending over a packet switching network.

IP-Internet Protocol

• Responsible for moving packets of data.

• IP Address

There are two different types of network operating systems

Client/Server

Peer-to-Peer

Client/Server

Allows the network to centralise functions and applications in one or more dedicated file servers.

Server

Computer running software that enables it to serve specific requests from other computers. The servers are usually more powerful computers and are held in a central location

Server will need server software such as Windows NT® Server or Novell Netware®.

Client

A computer, usually a desktop. Which accesses data/information from the server on the network. Will have its own processor. Which it uses.

Client networks need client software which is installed on the desktops.

Client/Server

Question? What services does a client/server network provide?

Advantages

• Resources and data security are controlled through the server. (Centralised)

• New technology can be easily integrated (adding more cables and stations)

• Expensive peripherals can be shared

• Backup routines can be easily implemented

Disadvantages

When server goes down, operations will cease across the network.

Cable failure can bring down a segment of a network

Large networks will require network managers to ensure efficiency across the network

Large networks require initial investment

Peer-to-Peer & Client-Server

Allows users to share resources and files located on their computers and to access shared resources found on other computers.

(Peer=equal) All machines have equal status.

Works well in the home or a small office.

Advantages

Cheap and easy to implement, no need for dedicated server

Easy to share files, access peripherals and have several people using the internet.

Disadvantages

Does not provide the security available on a client/server network

Organisation and management can become a problem

Backup can become difficult

Difficult to set up email. Only one email account.

Types of Network Servers

A network may have several types of servers.

• File servers • Print servers• Application servers• Email Servers• Web Servers

Network TopologyThe physical topology of a network is the way in which the cables and computers are connected to each other.

The main types of physical topologies are:

• Bus • Star • Ring• Mesh

Node

Processing locations on a network. A node can be any device attached to a network, for example, a workstation, a server, and a printer.

Every node has a unique network address.

Bus

Has a single communication cable, running the length of the network.

Uses coaxial cable.

All nodes are connected to a single channel.DIAGRAM

Advantages

• Easy to install

• Cheap to install

• Loss of a single node does not hinder the network

Disadvantage

• Fault along bus cable will affect whole network

• Network can have a slow response

Star

Connects all computers to one central server.

A high speed computer will act as the central controller which allows for very fast communication.

The cables used in star topologies are either shielded or unshielded twisted pair wires (STP or UTP).

DIAGRAM

Advantages

• If the link fails only the node connected will fail

• Provides high security

Disadvantage

• Cabling is expensive (lots needed)

Ring

Messages are passed along a chain.

Data sent around the network can potentially be accessed by any device hooked onto it.

Data travels in one direction.DIAGRAM

Advantages

• Supports high data transfer

• Easy to add other nodes

• High bandwidth

Disadvantage

• Expensive to install

• Difficult to install (Electronics)

Mesh

Multiple channels between nodes on the network

Data can be sent through one of several routes through the network.

DIAGRAM

Advantages

• Failure of a node or channel (cable) does not affect the network

Disadvantage

• Expensive to install (cables)

Some nodes on a network are devices which are there to manage the flow of data.

When data is sent it includes a destination address.

Each node on the network has its own address to uniquely identify it.

1. Hub

2. Switch

3. Router

Three common devices used for managing the flow of data are:

Stackable hubs with 8, 16 or 24 ports can be linked to form large LANS.

Nodes are connected to a hub via channels.

When data is received from a node it is broadcast to all the other ports.

It may also amplify the signal if long distances are involved.

This is inefficient as the data is intended for only one of the other nodes.

1. Hub

2. Switch

3. Router

HubA common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN.

A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

Advantage

• No installation needed

• Cheap

Disadvantage

• All devices on the network share the same bandwidth

It is also more secure as nodes only see the data which is intended for them.

A switch is sometimes known as an intelligent hub.

When data is received from a node it is examined and then sent directly to the destination known.

Switches are more complex than hubs and are therefore more expensive.

This is more efficient than a hub as the data goes directly to the destination node.

1. Hub

2. Switch

3. Router

Switch – ‘Smart Hub’

Will look at traffic it receives and based on the destination address it will direct the traffic to the port.

EtherFast 4124 24-Port 10/100 Ethernet Switch will boost your network performance

Advantage

• Devices don’t share the same bandwidth.

• Packet is delivered to address port.

Disadvantage

• Require additional set-up

• Expensive

They connect LANS to telecommunications lines and the Internet.

Routers connect different networks together.

They control and manage the flow of data over the different networks.

They cope with the differences in topologies and transmission media.

They connect smaller networks into larger internetworks.

1. Hub

2. Switch

3. Router

Router

Much of the work to get a message from one computer to another is done by routers, because they're the crucial devices that let messages flow between networks, rather than within networks.

A router links the two networks and connects both networks to the Internet.

Wireless Communications

Wireless communication increases flexibility of use and is becoming more popular for home, office and public spaces.

• No wiring required and ability to move around.

• Problems - Can be affected by electrical interference.

• Problems - Easy to hack into unless firewall security is enabled.

There are many technical reasons for the increasingly widespread use of networks. These include:

• Advances in computer hardware.e.g processor speed, main memory capacity, backing storage, data transfer rates.

• Improvements in network related software.

including network browsers and network operating systems

The use of networks which can be local, national or even international poses legal problems for governments.

Three Acts in particular are relevant for possible network misuse.

Computer Misuse ActThis Act makes it illegal to breach network security for any reason.

“Hackers” can be fined or imprisoned for gaining access and looking at or altering data and also for introducing viruses.

Copyright, Designs & Patents Act

This Act makes it illegal to make unauthorised copies of material.

Offenders can be fined or imprisoned for being involved in this activity and FAST(The Federation Against Software Theft) have had many companies and individuals prosecuted.

It is very easy on a network to transfer audio, video and text at high speed. This has led to a huge increase in the unauthorised pirating of music, films and books.

Data Protection Act(1998)

The Act gives individuals(Data Subjects) rights to:

• gain access to their data.

• seek compensation if inaccurate information causes damage.

• "opt-out" of having their data used for direct marketing.

• "opt-out" of fully automated decision-making about them.

The principles of this Act also apply to network use.

http://www.informationcommissioner.gov.uk/

Data Protection Act(1998)

Organisations processing personal data ("controllers") must comply with the data protection principles. These require data to be:

• fairly and lawfully processed.

• processed for limited purposes.

• adequate, relevant and not excessive.

• Accurate.

Data Protection Act(1998)

• not kept longer than necessary.

• processed in accordance with individuals' rights.

• kept secure.

• not transferred to non-EEA (European Economic Area) countries without adequate protection.

Select suitable hardware, including peripherals, to support the following tasks:

Producing a multimedia catalogue

Setting up a LAN in a school

Developing a school website

Describe how each piece of hardware will help with the task.

Network Interface Card (NIC)

Card inserted in a computer so that it can be connected to a network.

Hardware Factors

• Continuing bandwidth explosion ( 1Mb – 10Mb)

• Use of intensive applications and need for more bandwidth (streaming video & audio, Virtual private networks)

• Falling costs of setting up networks

Need to consider:

Processor

Memory

Backing Storage

Processor

Performance – execute and process many application at a high speed.

Flexibility – adapt to change in OS and applications.

Power – power consumption.

Software Support – Compilers, operating systems and libraries are available.

Memory

• Shared , distributed or a combination of memory

• Size and type used

• Cache memory

Backing Storage

Network storage is about storing data so that can accessed by network clients.

Clients

Server

Hard Disk

Software Factors

Browser

Program that enables a computer to look at and interact with WWW. Internet explorer and Netscape.

Network Operating Systems

Is run on the server.

• Novell

• Windows NT

• Windows 2000 Server

Workstation Operating Systems

NT Workstation

Windows 98

Mac OS

Bandwidth

A measure of the capacity of a communications channel. The higher a channel's bandwidth, the more information it can carry.

LAN

Depend on the number of people sharing the network

Reducing Demand

Data Compression

Data is compressed before it is transmitted then it requires less bandwidth.

Caching

Data is stored locally, then data only needs to travel over short distance.

Wireless

A wireless network allows computers to share printers, files or an internet connection without any wires between them.

Disadvantage

Lower bandwidth. Slower than cabling

Advantage

No cables around office

No disruption during installation of network

Move around office with laptop

Bluetooth

A global initiative by Ericsson, IBM, Intel, Nokia and Toshiba to set a standard for cable-free connectivity between mobile phones, mobile PCs, handheld computers and other peripherals.

Problems

Security

Encryption

A way of coding the information in a file or e-mail message so that if it is intercepted by a third party as it travels over a network it cannot be read.

Social Issues

Many people will become physically more isolcated from each other.

Third world countries

Ethical Issues

Netiquette

A way of behaving when connected to the internet or sending email messages.

• Not sending spam (unsolicited commercial emails)

• Not SHOUTING when sending emails

• Avoid sending large attachments

Reading pages

Questions

1.