Y8 CompSci - Unit 6 and Unit 7, The Internet / Decomposition, Abstraction

UNIT 6 KEYWORD: Data Packet

A small amount of data sent over a network. A header is attached to it providing extra info such as the source and destination address.

UNIT 6 KEYWORD: HTTP

Hypertext Transfer Protocol; important data transfer protocol used on the World Wide Web.

UNIT 6 KEYWORD: HTTPS

Hypertext Transfer Protocol Secure; secure data transfer protocol on the World Wide Web for transferring sensitive information.

UNIT 6 KEYWORD: Internet

A worldwide collection of computer networks linking together billions of digital devices.

UNIT 6 KEYWORD: Internet Protocol

A set of rules governing how devices communicate on the internet. This provides every computer on the internet with its own address.

UNIT 6 KEYWORD: Internet Service Provider (ISP)

An organisation that provides its customers with a connection to the internet.

UNIT 6 KEYWORD: Local Area Network (LAN)

Type of network that operates over a limited geographic area where everything is connected to a switch.

UNIT 6 KEYWORD: Packet Switching

A method of splitting data that is transmitted over a network into packets that travel to their destination independently and are reassembled in the correct order on arrival.

UNIT 6 KEYWORD: Protocol

A set of rules to allow communication between two computers.

UNIT 6 KEYWORD: Router

Hardware device which determines where to send data packets on a network, used to forward data from one network to another across the internet.

UNIT 6 KEYWORD: Server

A computer (program) which manages access to a centralised resource or service in a network.

UNIT 6 KEYWORD: Star Topology

Where every node is connected to a central node (switch).

UNIT 6 KEYWORD: Switch

A networking device that receives and forwards data to a destination node on a network without it passing through any other nodes en route.

UNIT 6 KEYWORD: Wireless Access Point (WAP)

A networking device that enables wireless devices to connect to a router to access the internet.

UNIT 7 KEYWORD: Procedural Abstraction

Removing unnecessary detail by grouping repeated elements into a named procedure that can be re-called.

UNIT 7 KEYWORD: Representational Abstraction

Removing unnecessary detail in our model of real-world objects by focusing on common characteristics to make them simpler.

UNIT 7 KEYWORD: Decomposition

The process of breaking down a single task/problem into several smaller tasks/problems to make it easier.

UNIT 7 KEYWORD: Subprogram

A smaller program within a larger program designed to perform a specific task that can be called by the main program or other subprograms when needed.

What can connecting local computers into a LAN enable? (3)

• Communication

• Sharing of data and devices

• Faster data transfer

Describe the most common arrangement of a LAN.

A star where all the devices are connected to a central device called a switch.

A networked device sends data as (1) which contains the (2) (3) of the (4) and (5) for the (6) to identify each device.

1. packets

2. MAC

3. Address

4. sender

5. recipient

6. switch

Each device in a LAN has a unique…

MAC Address

For a computer to send data to another in a LAN, what 3 things happen?
(Hint:

the… receives data from…

it looks up… using the…

it sends… onto the …)

1. the switch receives the packets from the sending device

2. it looks up the intended recipient using the MAC Address in the packet header

3. it then sends the packet onto the desired device

The 2 most common things used to connect all computers to a switch in a LAN is… (2)

• Ethernet copper cable

• WiFi radio signals

A home network is an example of a (1) where all the devices are connected to the (2) (acting as a switch) via (3) or an (4).

A switch may also contain a (5) to connect all devices wirelessly.

LAN

router

WiFi

ethernet copper cable

Wireless access point

What is the internet?

a group of computers connected all over the world that can communicate using cables that are made of glass fibres/copper wires or using radio waves with satellites.

Computers used everyday on the internet by people are called (1)

These are computers that can ask for (2) from (3) computer somewhere else in the world using a (4).

1. clients

2. information

3. another

4. server

What is a client?

A computer used by people in daily life that can request information from a server.

What is a server?

a computer that provides info to client computers such as websites.

Clients and servers send (1) to each other using (2) that form the (3). These (1 - again) are redirected to the right computer by (4).

1. packets

2. cables

3. internet

4. routers

To have access to a website, the (1) asks the (2) for information on the website and the (3) provides the (4) with that information. 

For these packets to know where to go, every computer on the internet has an (5) also known as an (6).

One is connected to the internet by one’s (7).

Routers do not use (8) to direct their packets; switches do that in LANs. Instead, they use (9).

Packets do not travel in a certain order; they just get (10) when they reach their destination.

1. client

2. server

3. server

4. client

5. Internet Protocol Address

6. IP Address

7. Internet Service Provider (ISP)

8. MAC Addresses

9. IP Addresses

10. re-arranged

The device provided by an ISP contains two things… 

• A (1) so that it can direct transmissions around your (2) (3) using (4) (5)

• A (6) so that it can connect your LAN to the (7) which is a (8) using (9) (10).

1. switch

2. home

3. LAN

4. MAC

5. Addresses

6. router

7. Internet

8. WAN

9. IP

10. Addresses

FILL IN THE BLANK:

A packet’s route on the internet is: 

1. Sent by the ________. 

2. Directed to the ________ on the LAN. 

3. Forwarded to the ________.

4. Passed through multiple ________ across the _________ until it reaches the ________. 

5. The _________ receives the packet, processes the ________, and sends packets containing the ________ back to the _______. 

client

switch

ISP

routers

internet

server

server

request

response

client

What is a packet’s route on the internet (5)

1. Sent by the client. 

2. Directed to the switch on the LAN. 

3. Forwarded to the ISP from the switch. 

4. Passed through multiple routers across the internet until it reaches the server. 

5. The server receives the packet, processes the request, and sends packets containing the response back to the client. 

The world wide web is one of the many (1) that runs on the (2).

It is a collection of (3) hosted on many different (4).

When you want to browse it, there is a (5) which is either (6) which stands for (7) or (8) which is more secure and stands for (9).

services

internet

web sites

web servers

protocol

HTTP

Hypertext transfer protocol

HTTPS

Hypertext transfer protocol secure

A web browser client software sends a HTTP(S) (1) to a web server, and the server sends a HTTP(S) (2) back to the client. 

The difference between HTTP and HTTPS is that…

1. request

2. response

3. HTTPS is more secure and harder for hackers to take data as everyone can access HTTP but not HTTPS.

FILL IN THE BLANKS:

The protocol for the WWW is that:

1. The client enters a _______ into the _______ software on your computer. 

2. Your _______ (the client) finds the ________ of the web server corresponding with the ______. 

3. The ________ sends the ________ to the server on the internet via your _______. 

4. The internet server sends a ________: a ________ file and any other _________ back to your computer (the client) 

5. When the ________ comes back, your ________ interprets and displays what it receives (or an error message if it cannot be found). 

URL

browser

browser

address

URL

response

HTML

resources

response

browser

What is the protocol for the WWW? (5)

1. The client enters a URL (Uniform Resource Locator) into the browser software on your computer. 

2. Your browser (the client) finds the address of the web server corresponding with the URL. 

3. The browser sends the request to the server on the internet via your ISP. 

4. The internet server sends a response: a HTML file and any other resources back to your computer (the client) 

5. When the response comes back, your browser interprets and displays what it receives (or an error message if it cannot be found). 

Advantages of abstraction. (3)

• Less code/storage if a repeated step in code is defined as a shorter subprogram. 

• Makes a program more ‘readable’. 

• Saves time; it takes less time to re-call a subprogram than to type it all out again. 

Advantages of decomposition. (2)

• Makes difficult/large tasks easier by breaking it down into smaller and more manageable tasks. 

• You can share the broken-down task with other people as a team so less overall time is taken.