Chapter 14 - Communication and Internet Technologies

Question 1

Why a protocol is essential for communication between computers

Answer 1

• Protocols set a standard for communication.
• all data is sent and received using the same rules and formats.
• Protocols enable communication between devices from different platforms.
• Communication is independent of hardware and software used.

Question 2

Show understanding of how protocol implementation can be viewed as a stack, where each layer has its own functionality

Answer 2

The protocols in a stack determine the interconnectivity rules for a Layered network module such as the TCP/IP model.

Question 3

TCP/IP

Answer 3

• A layered model with 4 layers
• Uses a set of protocols for transmission of data.

Question 4

4 Layers

Answer 4

• Application Layer: Provides user services
• Transport Layer: Handles packets
• Internet Layer: handles transmission using IP address
• Data link Layer: handles how packet is physically sent

Question 5

Application Layer

Answer 5

• Contains programs that exchanges data
• Sends files to the transport layer
• Allows applications to access the services used in other layers
• Defines the protocols that any app uses to allow the exchange of data

Question 6

File Transfer Protocols

Answer 6

• Anonymous FTP: access files anonymously
• FTP Commands: Carry out actions that can change files in FTP server
• FTP Server: Files that can be downloaded

Question 7

Application Layer Protocols

Answer 7

• HTTPS: for sending and receiving web pages (hypertext documents)
• FIP: For sending and receiving files over a network
• SMTP: For sending emails, push protocol
• POP3: For receiving emails, pull protocol

Question 8

IMAP

Question 9

Transport Layer

Answer 9

• Breaks data into manageable packets
• It controls the flow and sequence of the packets
• Sends them to the internet
• Handles packet loss.

Question 10

Internet Layer

Answer 10

• Identifies the extended network and host
• Transmits packets to the Data Link
• It routes the packets independently through the optimum route
• Addresses packets with source and destination IP address and uses them and port number to form a socket

Question 11

Data Link Layer

Answer 11

• To ensure correct network protocols are followed
• To enable upper layers to access the physical medium
• To form data into frames for transmission
• Maos IP address to MAC address

Question 12

How Applications use Bit torrent to exchange data

Answer 12

• Bit torrent software is made available
• A server called tracker keeps record of all the computers in the swarm and shares their IP addresses allowing them to connect with each other
• One computer in the swarm must have a complete copy of the torrent to be shared
• torrent is split into small pieces
• The prices of torrent are both uploaded and downloaded
• Once a computer has a piece, it becomes the seed and uploads
• Leeches download much more than they upload.

Question 13

What is Circuit switching

Answer 13

• A dedicated Circuit is established before transmission starts
• The whole bandwidth is used
• All data is transferred over the same route
  Eg: Video Streaming

Question 14

Where is Circuit Switching used

Answer 14

• When the whole bandwidth is required
• For real-time communications
  Eg: Video streaming

Question 15

Advantages of Circuit Switching

Answer 15

• Whole Bandwidth is available
• A dedicated channel increases the quality of transmission
• Data is received in the same order it has been sent so data does not need to be reassembled at the destination
• Simple method of data transmission and data can’t be lost

Question 16

Disadvantages of Circuit Switching

Answer 16

• A dedicated channel makes it impossible to transmit other data even if the channel is free
• No alternative route in case of failure
  -Not very secure as only one route is used
• Band width can’t be shared

Question 17

Packet Switching

Answer 17

• Date is equally split into packets
• Each packet is given its own route
• The routing of packets depends on congestion
• They might not arrive in the same order sent

Question 18

Where is Packet switching used

Answer 18

• Transmission of high-volume data
• For more security as packets are hashed and received in different routes
• In case of network change the packets are rerouted
• Data networks such as the internet to send large data files that do not need to be live-streamed
  Eg: Emails, VOPI

Question 19

Advantages of Packet switching

Answer 19

• More secure as hashed and take different routes to the destination
• Bandwidth can be shared
• Data reaches the destination with accuracy
• Missing packets can be detected and resent message is sent so the message arrives complete
• If the network changes the router can detect it and send the data another way ensuring it arrives

Question 20

Draw Backs of packet switchig

Answer 20

• Time delay as the packets need to be reassembled in the destination
• Uses complex protocols for transmission
• Not suitable for real-time transmission applications

Question 21

Explain how packet switching is used to pass messages across a network, including the internet

Answer 21

• A large message is divided into a small group of chucks the same size called packets.
• The packets have a header and payload
• The header contains the source and Destination IP address and sequence number
• Each packet is dispatched independently and many travel along different roots to the destination and reassemble
• If packet is missing a retransmission request is sent

Question 22

Show understanding of the function of a router in packet switching

Answer 22

• The router examines the packets header
• It reads the destination IP address
• The router had access to the routing table containing information of the gateway used and status of the routs along the route
• The route decides the best route and send the packet on to it’s next hop.