4.9.3.1 The Internet and how it works

Question 1

What is meant by the term packet switching?

Answer 1

Messages split into packets of equal sizes
Each packet given destination/source address
Each packet dispatched to the Internet through a router/gateway;
Packets sent independently and may travel a different route;
Packets given a packet/sequence number;
Routers forward packets (until they reach destination);
Best path of packet transfer determined by router/node(s);
Packets reassembled/reordered at the destination;

Question 2

Explain advantages of packet switching

Answer 2

Transmission is safer from interception because it is impossible to intercept all the packets as they use different routes
Very efficient use of network as each channel only used for short time / does not tie up a part of the network
If there is an error then only a small, identifiable, part of the data is affected this can be retransmitted easily

Question 3

What is the difference between the internet / world wide web

Answer 3

Internet - network of networks, networking infrastructure

WWW - way of transmitting information over the internet, interlinked documents and webpages on servers

Question 4

What is a router / gateway?

Answer 4

Routers - used to forward packets to another network. The router allocates IP addresses using DHCP protocol.
Gateway - A node in a network that connects two networks together, can be inside the router and used to access the internet
The router/gateway has an internal and external IP

Question 5

Explain how routing is achieved across the

Internet

Answer 5

The router analyses the header of the packet, the destination IP address, subnet mask, etc. and by using its routing table it will forward the packet into the best direction, depending on the amount of traffic.

Question 6

Describe the term ‘uniform resource locator’

URL

Answer 6

The protocol - e.g http / ftp
resource name includes: 
        sub domain e.g www,
        domain name e.g google, 
        top level domain e.g .com
file path - e.g index.html

Question 7

Explain the terms ‘fully qualified domain name’

(FQDN), ‘domain name’ and ‘IP address’

Answer 7

FQDN - the sub domain, domain name and top level domain. can then be turned into an Ip address using a DNS server
Domain name - used to identify one or more IP addresses. e.g microsoft.com

Question 8

What is a DNS server?

Answer 8

stores the url and its corresponding ip address so that the device can send a HTTP request to get the website
Takes a FQDN and returns an IP Address, maps FQDN to IP addresses

Question 9

Explain the service provided by Internet registries

and why they are needed.

Answer 9

There are regional internet registeries and national ones for countries, which are given a range of IP addresses they are allowed to use. They control how many IP addresses can be registered per country

Question 10

What is contained in a packet’s header information?

Answer 10

Port number
Destination IP / MAC address if known
Source IP / MAC
Packet number
Packet total
The data

Question 11

What is an IP address?

Answer 11

A numerical address stored in 4 bytes used to identify an individual computer or a network

Question 12

What is the intranet?

Answer 12

An internal website local to an organisation, which can only be viewed with access to the organisation

Question 13

What are the similarities between the internet and intranet?

Answer 13

Uses the same protocols and the same software to access them, both of them are used to share information and are client/server systems.
The internet is publicly available whilst the intranet is only accessible within a company, the intranet is private therefore it’s more secure.

Question 14

When is a DNS server unnecessary?

Answer 14

The local computer already has a copy of the IP address needed
The local computer has a cache of recent DNS queries.
The URL typed in already contains an IP address
The URL refers to a local resource e.g. file on the local computer.