J277.1.3.1.revision

1.3.Network revision

Types of networks

Factors that affect the performance of a network

Client-server and peer to peer to network

Hardware needed for local area network

The internet

Star and Mesh topologies

Types of network

LAN:

Local area network

A network that is formed when devices in the same building or on a single site are connected.

Types of network

characteristic of LAN:

one characteristic of a local area network is that the infrastructure (cabling and network communication devices) will be owned and maintained by the organisation (or they may employ someone to do this for them).

Types of network

WAN:

When two or more networks are connected across a large geographical area, they form a wide area network (WAN).

e.g. Bank connecting all of it's cash machines together across the country.

Types of network

characteristic of WAN:

Many wide area networks will make use of telecommunication links owned and managed by other companies.

Organisations that run their own WANs will often lease bandwidth from telecommunications companies.

Technologies exist to allow different organisations to transmit securely across shared or public communication links.

Multiple Choice

What is a Local Area Network (LAN)?

• A group of computers and other devices owned by the same company

• A group of computers and devices spread over a large geographical area

• A group of computers and devices located within a single building

• A group of computers and other devices located on a single site

Multiple Choice

A network set up across a school site is an example of a…

• Wide Area Network

• Virtual Area Network

• Personal Area Network

• Local Area Network

Multiple Choice

Which of the following statements does not match the description of a LAN?

• Located over a large geographical area

• Covers a small geographical area

• Wired with UTP cable and fibre optic

• All hardware is usually owned by the organisation using it

Multiple Choice

Which of the following are not typically used for data transmission on LANs?

• Copper cable

• Wi-Fi

• Fibre optic

• Satellite links

Multiple Choice

What is a Wide Area Network (WAN)?

• A group of computers and devices located within a single building

• A group of computers and devices spread over a large geographical area

• A group of computers and other devices located on a single site

• A group of computers and other devices owned by the same company

Multiple Choice

Hospitals, banks and supermarkets are all linked using which network type?

• WAN

• LAN

• BUS

• WiFi

Factors that affect the performance of network

Bit rate- Bit rate is the measure of the amount of data (in bits) that is transferred per second.

Bandwidth- Bandwidth is the theoretical maximum amount of data that a communications channel can carry at one time.

Network range- The range of a network is the distance over which data can be reliably transmitted. The most important component in determining range is the transmission media.

Number of devices connected-

Latency

Factors that affect the performance of network

Number of devices connected-

All of the devices on a local area network will share its bandwidth.

In most LANs, whether wired or wireless, only one device can communicate at a time and this means that a busy network will be much slower than a quiet network.

Strictly speaking, it is not the number of devices on a network that impacts network speed but what these devices are doing.

Factors that affect the performance of network

Latency-

Latency is the delay between the time a signal is transmitted and the time a signal is received.

Some communication systems have naturally high latency. For example, there is a delay of around a quarter of a second for a signal from a ground-based transmitter to reach a satellite in geostationary orbit.

Multiple Choice

Which of the following factors does not have a major impact on network performance?

• Wireless SSID

• Bandwidth

• Latency

• Errors in transmission

Multiple Choice

Which factor affecting the performance of a network is described as: 'the amount of data that can be sent and received in a given time. This is not a measure of how fast data travels, but how much data can be sent on the transmission media.'

• User load

• Latency

• Bandwidth

• Error rate

Multiple Choice

Which factor affecting the performance of a network is described as, 'the delay from transmitting data to receiving it.'

• Transmission media

• Error rate

• Bandwidth

• Latency

Multiple Choice

What is the most likely affect of installing CCTV cameras to an existing network infrastructure?

• The devices will not work

• The performance will increase

• The performance will decrease

• There will be no change

Client server network

Client–server networks allow you to access your files and emails from any authorised device.

Client server network

A server is a program on a computer that shares resources with, or provides services to, any authorised client.

There are many types of server:

• File servers store and provide files.

• Web servers store and provide webpages.

• Email servers store and forward emails. Some email servers filter out spam.

• Database servers store databases, run queries, and allow data to be manipulated.

• Print servers provide printing services across the network and manage print queues.

Client server network

A client is a program that typically runs on a device used by an end-user such as a laptop or mobile phone.

A client sends a request to the server.

The server processes the request and then sends a response back to the client. For example, when you want to view a webpage, you will use a web browser (which is a web client).

The browser will request the page from a web server. The server will send the page back to the browser and the page will be displayed.

Peer to peer network

In a peer-to-peer network, there are no central servers. Every computer can be configured to share its resources.

This can involve sharing files (e.g. games, movies, and music), software, processing power, or internet bandwidth. Peers can also share hardware such as printers or optical disc drives.

Peer to peer network

Computers must be switched on to share resources. Peers communicate directly with each other.

The owner of each device gives permission to access some or all of the device's resources.

This needs to be done with care; if you give someone write-access to your disk drive, they would be able to delete all of your files.

Multiple Choice

All the user files are stored on one drive and access is restricted by the central network operating system. What type of network is most likely being described?

• Virtual network

• Peer-to-peer

• Client-server

• Metropolitan area network

Multiple Choice

A characteristic of peer-to-peer networking is…

• A single point of failure - users will lose access if the server fails

• Easy to manage security of files

• It can be difficult to maintain a well ordered file store

• Can be expensive to set up and maintain

Multiple Choice

A characteristic of client-server networking is…

• The network is less secure

• No dependency on a single machine

• Cheaper to set up - no expensive hardware required

• Requires IT specialists to maintain

Multiple Choice

Which of the following is not a characteristic of the client-server model?

• Central server manages access to the internet

• Computers make requests to server for data and connections

• Each computer responsible for its own security

• Easier to install software updates

Multiple Choice

A characteristic of client-server networking is…

• High security of access to files

• Users will need to manage their own backups

• Very easy to maintain - specialist staff are not required

• No dependency on a single machine

Multiple Choice

A characteristic of peer-to-peer networking is…

• Easy to maintain - specialist staff are not required

• Easy to install software updates

• Easy to manage security of files

• Easy to take backups of all shared files

Multiple Choice

All the user files are stored on one drive and access is restricted by the central network operating system. What type of network is most likely being described?

• Virtual network

• Peer-to-peer

• Client-server

• Metropolitan area network

Multiple Choice

Which of the following is not a characteristic of the peer-to-peer model?

• Each computer uses a central server to manage printing

• Each computer is responsible for its own security

• Each computer is responsible for backing up its own data

• Each computer is considered equal

The internet

The internet is a global system of interconnected computer networks.

The internet facilitates a wide range of services, including the World Wide Web, email, internet telephony, and file sharing.

In order to communicate to do any of those things, computers must use a common set of protocols referred to as the TCP/IP stack.

Domain name system(DNS)

Whenever you want to browse a website, play an online game, or collect your email, you need to access the relevant server via its specific IP address.

Most servers have a user-friendly name that saves us from having to remember its IP address. These are called domain names and each domain names maps to a specific IP address.

Domain name service(DNS)

Domain names are usually chosen to represent the name of the company or organisation that is providing a service, so they are often easy to guess.

The domain name system converts domain names to the IP addresses needed to locate resources on the internet.

The domain name system converts domain names to the IP addresses needed to locate resources on the internet.

Domain name service

The domain name service (DNS) comprises multiple domain name servers.

The role of a domain name server is to look up a domain name to find the corresponding IP address, so that content from a server located at that IP address can be requested and sent to the user’s computer.

Domain name service

The domain name service (DNS) comprises multiple domain name servers.

The role of a domain name server is to look up a domain name to find the corresponding IP address, so that content from a server located at that IP address can be requested and sent to the user’s computer.

Example

When a user enters a URL (e.g. https://www.raspberrypi.org/learn/index.html) into a web browser's address bar, this sequence of events happens:

• The browser sends the domain name part of the URL, including the ‘www’ part (e.g. www.raspberrypi.org), to a domain name server. This is usually provided by your ISP.

• The domain name server checks for the URL in its lookup table

• The domain name server sends the corresponding IP address back to the browser

• The browser sends a request for the resource identified in the path (/learn/index.html) to the web server located at the IP address

• The resource is then returned to the browser

What happens if the URL is not in the domain name server's lookup table?

This is why the domain name system comprises multiple domain name servers. There is a hierarchy of DNS servers based on the hierarchical structure of the domain names.

Imagine we are looking to resolve www.raspberrypi.org

• 'org' is the Top Level Domain.

• 'raspberrypi' is the Domain.

• 'www' is the Subdomain.

If the local domain name server does not find the URL in its lookup table, it passes the request to a Top Level domain name server.

There are separate servers for most of the top-level domains such as '.com' , '.org' and '.uk', each administered by a different authority.

The request is therefore passed to the domain name server for '.org'

Multiple Choice

What does DNS stand for?

• Detailed Name Server

• Dominate Naming System

• Dedicated Naming System

• Domain Name Server/System

Multiple Choice

What is the purpose of a Domain Name Service?

• To prevent more than one URL mapping to the same IP address

• To allow users to connect to The Internet to retrieve webpages

• To store copies of websites to serve to users when they type in URLs

• To maintain an index of mapped URLs to IP addresses and serve web pages

Multiple Choice

What is the name for a service which translates a web address into an IP address?

• Dominate Naming Server

• Domain Name Service

• Dedicated Name Server

• Domain Nominated Server

​What is the cloud?

The term 'the cloud' refers to a set of computing services that are accessed over the internet.

Cloud computing services are run out of server farms: huge warehouses full of servers attached to extremely large storage devices.

​What is the cloud?

The term 'the cloud' refers to a set of computing services that are accessed over the internet.

Cloud computing services are run out of server farms: huge warehouses full of servers attached to extremely large storage devices.

Cloud services allow users to run applications and use storage online.

​The cloud services

Storage- Online storage for it's users e.g. one drive, G-drive

Computation- Using server farms for additional processing power. e.g. creating 3d models or task that will require 6 hours on normal computer.

Software as a service( SaaS)- cloud applications - IaaS provides web hosting, data centres, servers, and storage networks that are all hosted by the service provider.

Multiple Choice

What is meant by 'the cloud'?

• A collective term for a company intranet

• It is another term for 'the internet', or 'world wide web'

• Remote servers that store data and software that can be accessed over the internet

• It refers to the DNS server which links your requested URL to an IP address

Multiple Choice

Which of the following is an advantage of storing data in 'the cloud'?

• Security of access to files is increased

• It makes collaboration on a file a possibility

• Malware is less likely to spread to other computers

• The byte-for-byte cost of storing data is lower compared to local drives

Multiple Choice

Which of the following is an advantage of storing data in 'the cloud'?

• Security of access to files is increased

• Automatic backups can be taken

• It does not require a username and password to access

• Malware is less likely to spread to other computers

Multiple Choice

Which of the following is a disadvantage of storing data in 'the cloud'?

• Automatic backups can be taken

• Access to files anytime, anywhere

• The cost of large volumes of storage

• It gives you the ability to easily share files

Multiple Choice

Which of the following is an advantage of storing data in 'the cloud'?

• The byte-for-byte cost of storing data is lower compared to local drives

• Malware is less likely to spread to other computers

• Security of access to files is increased

• Access files anytime, anywhere

Topologies

The different arrangements of computer connections and devices are called topologies.

Star and Mesh topologies in your spec.

each device on the network is connected to a central communication device, such as a Hub or a Switch

​

Star topology

a switch uses a table that maps each device to the port it is connected to. In this way, the switch is able to direct messages to the correct recipient (receiving device).

Switch

network signals that reach the hub are sent out to all connected devices.

Hub

Hub or Switch

Central switch fails then network will fail.

Central point of failure

Disadvantages

Easy to add or remove individual devices.

Individual cable failure would not affect network.

Individual station failure would not affect network.

Advantages

Features of star topologies

Mesh Topology

In a mesh network, there is no central communications point.

Instead there are multiple paths between the communication devices (e.g. switches and routers) that form the network.

Each communications device connects directly, and non-hierarchically, to as many other communication devices as possible to provide many communication pathways.

Each communications device connects directly, and non-hierarchically, to as many other communication devices as possible to provide many communication pathways.

​Most messages that are sent across the internet are broken into multiple packets and each packet can take a different path from source to destination.

At the end point, the packets are put back into order using a sequence number that is part of the packet's header information.

Multiple Choice

What is a network topology?

• How the network interacts with other devices

• A layout of a network

Multiple Choice

The advantage of a star network is

• It uses less cable than other topologies

• It requires no extra hardware such as hubs and switches

• It is easy to install and expand with extra nodes

• It is unaffected by a breakdown of the central computer

Multiple Choice

What type of topology is this?

• Mesh

• Ring

• Star

• Line

• Bus

Multiple Choice

Which network topology needs a switch or hub?

• Mesh

• Partial Mesh

• Star

• Bus

Multiple Choice

This is what kind of topology?

• BUS

• RING

• STAR

• MESH

Multiple Choice

Each node is connected to every other node.

• Partially-connected mesh topology

• Mesh topology

• Fully-connected mesh topology

• Semi-connected mesh topology

Multiple Select

Which of these are disadvantages of mesh topology?

• They are slower.

• The cost of building the network is higher.

• They are only compatible with certain computers.

• The network requires more maintenance.

Multiple Choice

Which of these is an advantage of mesh topologies?

• They allow you to communicate over long distances.

• They make the computer run faster.

• They are easy to build.

• Many devices can transmit data simultaneously.