1.3.2 Networks

Question 1

What is a protocol?

Answer 1

A set of rules to govern communication across a network.

Question 2

What are some examples of protocols?

Answer 2

TCP
IP
POP
SMTP
IMAP
FTP

Question 3

What are the benefits of protocols?

Answer 3

Allow networks to communicate by ensuring all devices follow the same rules

This means devices interpret data in the same way

Question 4

Define and give examples of a standard.

Answer 4

An agreed way of doing things like USB, HTML, MP3

Question 5

What is the benefit of standards?

Answer 5

Standards make it easier for people to build programs and software that work on different systems in different countries.

Question 6

What is a DNS, and what is its purpose?

Answer 6

Domain Name System (DNS)

Used to convert a given URL to a corresponding IP address.

Question 7

What is the process used by a DNS?

Answer 7

URL (www.google.co.uk) is entered and sent to the DNS resolver

DNS servers map this domain to an IP address, by looking up in a lookup table/cache.

If the DNS server cannot find it, it passes the request (recursively) to the top-level domain name server.

If the IP address is found it updates the DNS servers that did not know it.

If it is not found then it will return an error

The original DNS Server sends the IP address to the browser so it can retrieve the website from the server on which it is hosted.

Question 8

What is an IP address?

Answer 8

Uniquely identifies a device on a network.

An IP address is a logical identifier. (e.g. 192.168.0.1)

Question 9

State the four layers of the TCP/IP Stack.

Answer 9

Application
Transport
Internet
Link

Question 10

Describe the application layer and give an example of a protocol used at this layer.

Answer 10

Sits at the top of the stack.
If a browser is used, then it will use HTTP protocols

Question 11

Describe the transport layer and give an example of a protocol used at this layer.

Answer 11

Uses the Transmission Control Protocol (TCP) to establish an end-to-end connection

Splits the data into packets

Adds the packet number, total, and port.

Question 12

Describe the internet layer and give an example of a protocol used at this layer.

Answer 12

Routers operate on this layer
Adds the IP address to the packet (to/from)

Question 13

Describe the link layer of the TCP/IP stack.

Answer 13

Source and destination MAC addresses added.

Question 14

What are the benefits of protocol layering?

Answer 14

Allows different layers to be worked on independently.

Allows layers to be upgraded without affecting others.

Allows for layers from different providers to be used interchangeably.

Question 15

What is a LAN?

Answer 15

LAN – Local Area Network

A group of devices connected over a small geographical area.

The equipment is owned by the network owner.

The range could include a building or campus.

Question 16

What is a WAN?

Answer 16

WAN – Wide Area Network

A group of devices connected over a large geographical area

Often uses third-party communication channels.

Range could include the entire world

Question 17

Define circuit switching and its associated pros and cons.

Answer 17

Creates a direct link between two devices for the duration of the communication. The public telephone system is an example.

• The connection is set up for the entire duration of the message so
  bandwidth is wasted during the periods when no data is being sent.
• The two devices must transmit and receive data at the same rate

+ Data packets arrive in the same order that they are sent, simplifying the process of reconstructing the message at the recipient end.

Question 18

Define packet switching.

Answer 18

Data is split into equal-sized packets.

Each packet has a header of information (including the destination address and the place of the packet in the complete message)

Each packet is placed on the network, each may travel by a different route, meaning they may arrive at different times.

At each node on the network, the destination address is read, and the best route is found.

Packets need to be reordered at the destination.

Question 19

What are the three benefits of packet switching?

Answer 19

Transmission is safer from interception because it is impossible to intercept all the packets as they use different routes.

Very efficient use of the network as it 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, and this can be retransmitted easily.

Question 20

What is a network?

Answer 20

A collection of two or more computers connected in order to exchange information and share resources.

Question 21

Why might someone use a network?

Answer 21

File and Data Sharing

Resource Sharing (Printers etc..)

Data Protection and Redundancy

Ease of Administration

Distributing Computing Power

Internal Communications

Question 22

What is a client-server network?

Answer 22

Client computers connect to and are controlled by a central server

The server provides access to a resource/service (depending on the user)

Question 23

What are the pros and cons of client-server networks?

Answer 23

+ Centrally administered in one location, including pushing out S/W updates and security patches.

+ One location to back up (file server)

+ Shared resources such as printers are not tied to a single computer

• Has a central point of failure (server)
• Can be expensive to maintain/set up (e.g. cabling costs, specialist staff.)

Question 24

What are the pros and cons of peer-to-peer networks?

Answer 24

+ Has no central point of failure

+ Cheap to set up and run.

• Multiple locations to back up
• Devices have to maintain their own security.
• Shared resources are lost when the connected computer is offline

Question 25

What is a peer-to-peer (P2P) network?

Answer 25

A network with no central server where all devices have equal status.