Unit 10 - The Internet

Question 1

What is the backbone of the internet?

Answer 1

The backbone is a set of dedicated connections that connect several large networks at various points across the world. These networks are connected to other regional networks, often controlled by ISPs.

Question 2

What is the name for the “www.bbc.co.uk” in “www.bbc.co.uk”?

Answer 2

It is a FQDN (Fully Qualified Domain Name).

Question 3

What is the name for the “www” in “www.bbc.co.uk”?

Answer 3

It is the host.

Question 4

What is the name for the “bbc.co.uk” in “www.bbc.co.uk”?

Answer 4

It is the domain name.

Question 5

What are the three components of a URL? (refer to http://www.bbc.co.uk/index.html for help)

Answer 5

• The protocol
• The Fully Qualified Domain Name
• The resource being accessed

Question 6

What is the purpose of DNS (Domain Name System) servers?

Answer 6

DNS servers are dedicated computers containing an index of domain names and their corresponding IP addresses.

Question 7

What are the five global Internet Registries and their purposes?

Answer 7

The five global Internet Registries are registries responsible for allocating IP addresses to specific domain names. This is to ensure all IP addresses are unique.

Question 8

What is the process of a data packet routing between networks?

Answer 8

Routers have information stored about available routes to the target destination. They then choose the best router to forward the packet onto, each pass is called a “hop”.

Question 9

What are the three components of a packet?

Answer 9

A packet contains a header, a payload and a trailer.

Question 10

What information is contained within a packet header?

Answer 10

• Recipient’s address
• Sender’s address
• Hop limit/TTL (Time To Live)

Question 11

What is contained within a packet trailer?

Answer 11

The packet trailer contains error checking components that verify the received data hasn’t been corrupted.

Question 12

When is a gateway required between networks?

Answer 12

A gateway is required when then two networks use different protocols and are often combined with routers. They modify data in the header to suit the change in protocols.

Question 13

What does a firewall do to protect a network?

Answer 13

Firewalls only open specific ports that allow certain packets to pass through while blocking others.

Question 14

Packet filtering process:

Answer 14

• Data packets are inspected by firewall

- If the packet is to be allowed through, the firewall temporarily opens the required port.

Question 15

Stateful inspection process:

Answer 15

The firewall inspects the payload of the packet before allowing access and remembers actions for future decisions.

Question 16

Functions of a proxy server:

Answer 16

• Makes web requests on behalf of a computer, hiding the request IP address from the recipient.
• Enables anonymous surfing.
• Can filter undesirable online content.
• Logs user data with their requests.
• Holds a cache of recently visited websites.

Question 17

The four layers of the TCP/IP protocol stack:

Answer 17

• Application layer
• Transport layer
• Network layer
• Link layer

Question 18

Purpose of application layer:

Answer 18

Provides services for applications that want to communicate across a network, such as SMTP and FTP protocols. Doesn’t actually sent the data, just decides the rules.

Question 19

Purpose of transport layer:

Answer 19

Uses TCP to establish a connection between sender and receiver. Data is split up into multiple packets, adding the port to be used. This layer at the receiving end confirms that packets have been sent and requests resends of those that are lost.

Question 20

Purpose of network layer:

Answer 20

Uses IP to address packets with source and destination IP addresses. Routers forward the packet towards the endpoint (socket) via a routing table.

Question 21

Purpose of link layer:

Answer 21

Adds the MAC address of the physical NIC that packets should be sent to at the IP address. MAC addresses change with each hop.

Question 22

What happens in the TCP/IP process when a message is recieved?

Answer 22

The message is passed back up through the layers, stripping what they each added. e.g. the link layer removes the MAC address.

Question 23

What is SSH?

Answer 23

SSH is an encrypted protocol that allows secure communication between nodes across a network.

Question 24

What does SSH do?

Answer 24

SSH can be used to create a tunnel through a network. This tunnel can allow passage of data that might usually be blocked.