13a The Internet

Question 1

What is the internet?

Answer 1

A wide area network connecting smaller networks around the globe together using established protocols.

Question 2

What is an intranet?

Answer 2

A private network within an organization. Operating using World Wide Web technology.
E.g. the school timetable login

Question 3

What is an extranet?

Answer 3

Extranets are intranets that can be partially accessed by external organizations allowing closely related businesses access.

Question 4

What is a URL?

Answer 4

Uniform Resource Locators are strings of characters that refer to the location of an internet source.

Question 5

How is the domain name (URL) below split up?
http://www.bbc.org.uk/index.html

Answer 5

http - protocol used to transfer information
www - third level/sub domain indicates the type of server being connected to
bbc - second level domain/domain name
org.uk - top level domain indicates country registered to and company type
index.html - page/path

Question 6

What is an IP address?

Answer 6

When joining a network the device is assigned an IP address not being used in that network. When it leaves, that IP becomes available again.

Question 7

What are the two different forms of IP?

Answer 7

IPv4 - 4 8 bit digits e.g. 234.57.255.123
IPv6 - 6 8 bit digits

Question 8

Why is IPv6 needed?

Answer 8

We ran out of combination of IPv4 so an extra 16 bits were added allowing for a possible 2^48 different combinations.

Question 9

What is a DNS?

Answer 9

A domain name server holds a database of URLs and the corresponding IP.

Question 10

If the DNS cannot map a domain name what happens?

Answer 10

The domain name is sent to other nearby servers until it is mapped to an IP.

Question 11

Why aren’t DNS’ always required?

Answer 11

The address may be stored locally if regularly accessed.
If the IP is entered directly.
If the URL refers to a resource stored locally.

Question 12

What port is used for websites?

Answer 12

Port 80

Question 13

What is a port?

Answer 13

Ports allow the device to tell which application should handle the data being received. Each port has a unique number to identify it. They are the points at which data is transferred

Question 14

What do port scanners check?

Answer 14

If the port is open
If the port is filtered
This is done by sending a request to the port and seeing its response

Question 15

What is SSH?

Answer 15

Secure shell protocol allows remote access to computers

Question 16

How can hackers abuse port scanning?

Answer 16

Use it check if there are open ports and send malicious data to those ports.

Question 17

What is a non routable ip?

Answer 17

A private IP that is only used for communicating in a LAN and isn’t used for internet access

Question 18

How does network address translation work?

Answer 18

All devices in a LAN are connected to a router. When the device tries to access the internet the router replaces its private IP with its own public IP.

Question 19

What are the advantages of Network address Translation?

Answer 19

Devices don’t all need a unique IP to join the internet.
More secure as the private IPs are not broadcasted.

Question 20

What is an API?

Answer 20

Allows two software applications to communicate.
E.g. google maps API is integrated into apps such as just eat

Question 21

What is a socket?

Answer 21

Sockets are the combination of an ip address and a port number.
The socket represents the destination for data.

Question 22

What is a web socket?

Answer 22

Web sockets are a higher protocol built on top of sockets that are specifically used for real time communication.
They use http/s

Question 23

What are subnets?

Answer 23

Segmented pieces of larger networks

Question 24

What are the benefits of web sockets?

Answer 24

Fast
Always open
Real time

Question 25

What are the types of web socket?

Answer 25

Simplex - one way Half duplex - both ways Full duplex - both ways at the same time

Question 26

What is subnetting?

Answer 26

A network is divided into segments

Question 27

What is subnet masking?

Answer 27

The process of dividing an ip into two parts. One for identifying the network and one for the host/device.

Question 28

How does subnet masking work?

Answer 28

A subnet mask is a 32 bit number similar to an ip. When anded with the ip the subnet mask returns the network id.

Question 29

Give the subnet mask for an ip which has a network number 24 bits large

Answer 29

255.255.255.0 When anded with the subnet IP the ones will return whatever is in the ip but the 0 will return nothing.

Question 30

What is DHCP

Answer 30

Dynamic host configuration protocol allows IP addresses to be reused by allocating devices on a network dynamic IPs that other devices can use when that device leaves.

Question 31

What is a gateway?

Answer 31

A gateway connects two different networks together like a router. It can also connect networks using two different protocols.

Question 32

What is a router?

Answer 32

Receives packets on a network and forwards them to the correct destination based on the address.

Question 33

How does packet switching work?

Answer 33

Method for sending data by dividing it into packets. 1. Messages are split into packets 2. Each packet is assigned a destination and sequence number 3. Packets are sent independently through a router 4. Routers forward packets until they reach the destination 5. Packets reassembled in order

Question 34

How are packets declared lost and what happens to lost packets?

Answer 34

Each packet is assigned a hop count which decrements each time it transferred between routers. If the hop count reaches 0 the packet is declared lost and is resent by the source.

Question 35

Name two advantages of packet switching

Answer 35

1. More secure 2. Less stress on cables

Question 36

What are 3 disadvantages of packet switching?

Answer 36

1. Easy to lose packets in high traffic times 2. Not good for real time applications as it is slow 3. If the file is small it isn’t worth splitting into packets

Question 37

What do internet registries do?

Answer 37

They are company’s that control the assigning of domains and IPs in certain regions.

Question 38

Why are internet registries needed?

Answer 38

To ensure each device on the internet has a unique IP address.