1.1 Networks and protocols

Question 1

What is a network?

Answer 1

When two or more computers (nodes) are connected (wirelessly or wired) to each other used agreed protocols to communicate

Question 2

What is are network protocols?

Answer 2

A set of rules that govern how data is transmitted on a network

Question 3

What are the two server types?

Answer 3

Client Servers (CS)
Peer to Peer (P2P)

Question 4

What is a Client Server?

Answer 4

A network where different types of servers control the network and the clients (computers) send requests to use services and resources of these more powerful servers via a LAN or WAN

Question 5

What us a Peer to Peer server?

Answer 5

A simpler network where there is no central server controlling the network, instead the peers (nodes) are connected to one another and share/ access necessary recourses. Access rights to resources and services are authorised by setting sharing permissions on each computer. They can also download separate parts of a big file to improve download speeds

Question 6

What are the advantages and disadvantages of a Client Server?

Answer 6

Advantages
- Faster at processing tasks
- Can manage very large networks
- Easy Access to central data
Disadvantages
- If the server/ cable fails no user can continue to work
- More expensive and complicated to set up due to hardware and software
- Requires specialist personnel to manage systems

Question 7

What are the advantages and disadvantages of a P2P server?

Answer 7

Advantages
- Less vulnerable to central server crashes
- Simple to set up and maintain
- Initial start up cost is less and the operating systems are less complicated

Disadvantages
- Slower at processing tasks
- Only works well on smaller networks (e.g. <15)
- Security and backup are not centralised and are difficult to manage

Question 8

What are the network protocols to know?

Answer 8

TCP/ IP - Transmission Control Protocol/ Internet Protocol
FTP - File Transfer Protocol
DHCP - Dynamic Host Configuration Protocol
HTTP - Hyper Text Transfer Protocol
SMTP - Simple Mail Transfer Protocol
IMAP - Internet Message Access Protocol
UDP - User Diagram Protocol

Question 9

What is UDP?

Answer 9

• User Datagram Protocol is an alternative transport layer to TCP
• It sends messages instead of data packet which is much faster and has lower-latency.
• Therefore, it is used in time-sensitive transmission such as for gaming or video calls
• But can be unreliable as it does not setup a pathway before transmission

Uses messages, low-latency, less reliable (no pathways)

Question 10

What is TCP?

Answer 10

A protocol that slits data into data packets that are routed across a network and puts together at the end using the sequence number.

It adds reliability to packet delivery by adding a destination address, source address and error check so the packet will be sent to the source if an error occurred.

Question 11

What is FTP?

Answer 11

A protocol that governs the transfer of files across the internet between the server and client

Question 12

What is DHCP?

Answer 12

Dynamic Host Configuration Protocol automatically assigns each device in a network with a temporary network address out of available locations. Once it goes offline the address can be used by another device and can therefore change each time we use the internet.
This is how almost all people access the internet

Question 13

What is HTTP?

Answer 13

A protocol that transfers web pages from a web server to a client computer’s web browser

Question 14

What is SMTP?

Answer 14

Simple Mail Transfer Protocol sends and receives email messages from a client to a server

Question 15

What is IMAP?

Answer 15

Internet Message Accesses Protocol allows email messages to be accessed from a mail sever without it being deleted (allowing it to be accessed on multiple devices).

Question 16

What is the TCP protocol stack layers

Answer 16

Physical layer
Data layer
Network layer
Transport layer
Application layer
(Pineapples Do Not Trust Apples)

Question 17

What happens in the Physical Layer?

Answer 17

Converts data from the data link layer into bits and then transmits this raw data either electronically or optically.

Question 18

What happens in the Data Link Layer?

Answer 18

Defines how data will be physically transferred across the network by giving packets MAC addresses (destination and source) which will send it to the next router.

Question 19

What happens in the Network Layer?

Answer 19

This is when the packet is provided with an IP destination and source address
The routers work on this layer

Question 20

What happens in the Transport Layer?

Answer 20

• Establishes the connection between two different computers or ‘hosts’- an “end to end” connection
• Once the connection is made, it will split the data into packets with it’s sequence number
  TCP/UDP

Question 21

What happens in the Application layer?

Answer 21

• Selects a correct protocol to use depending on which application it is and what you are trying to do and requests connections. (E.g. HTTP for websites, IMAP/ SMTP for emails)

Question 22

How is traffic routed on a packet switched network?

Answer 22

Firstly, the data is split into packets that each have a destination address and a sequence number. These packets are then routed along the lowest cost (fastest) route by routers until they are reassembled at the destination address using the sequence number

Question 23

What is a data collision and how can this problem be solved?

Answer 23

This is when two sets of data are detected simultaneously. To solve this problem, the computer waits a short random amount of time until the data is sent again.

Question 24

Why are protocols put into stacks?

Answer 24

• Separation of logic (protocols) means that a single protocol can be dealt with in isolation- Easier to debug
• Protocols at different parts of the stack can be swapped out depending on the application
• Much more flexible when choosing what properties you want your network to have

Question 25

What are MAC addresses and their purpose in the TCP/IP stack

Answer 25

Media Access Control addresses are the address of a network interface card (NIC) that is factory loaded onto them.
Packets will be sent from one router to another using the MAC addresses of each one and the IP address of the destination

Question 26

What is simplex transmission mode?

Answer 26

When only one of the two devices can transmit and the other can only revive. (E.g. a radio)

Question 27

What is a half duplex transmission mode?

Answer 27

When each device can send and receive but not at the same time (e.g. a walkie talkie)

Question 28

What is handshaking?

Answer 28

A process in which two communicating devices agree on a set of protocols to use

Question 29

What is full duplex?

Answer 29

When data can travel in both directions at the same time. (e.g. a telephone/ video call)

Question 30

What is multiplexing?

Answer 30

This is where several independent data sources are combined and sent along a single route to a single destination. Several data streams can be combined and transmitted over the same wire

Question 31

What is the internet?

Answer 31

This is the physical networks of different networks which spans the globe. The physical connection between all devices

Question 32

What is the world wide web?

Answer 32

This is the web pages you see and interact with by your device communicating with a webserver over the internet