Section 5 - Networks and web technologies

Question 1

What does URL stand for?

Answer 1

Uniform Resource Locator

Question 2

What does the DHCP do?

Answer 2

It dynamically gives any connecting clients a private IP on a network

Question 3

Why does DHCP give dynamic IP addresses?

Answer 3

So that the IP you connect to constantly changes and so can’t be accessed through other methods

Question 4

Why is the first checked server in the DNS tree the local client?

Answer 4

The local client server has a catch memory of previously visited websites so can be accessed quickly without finding the address in the DNS servers.

Question 5

What is the difference between physical and logical topologies?

Answer 5

The physical topology is how the devices are physically connected (cables etc) and the logical topology is how the devices communicate on the server.

Question 6

What is circuit switching?

Answer 6

Creating a communication network between two endpoints for the duration of a phone call or file transfer.

Question 7

What is a transfer between two routers known as?

Answer 7

A hop

Question 8

What data about a network does a router hold?

Answer 8

The available routes to the destination node.

Question 9

What does a router do?

Answer 9

Look up the destination IP address in its routing table to find the best router to send a packet.

Question 10

What’s the difference between a router and a hub?

Answer 10

A hub doesn’t know where data needs to go or the fastest route to get there. The router knows both.

Question 11

What is the difference between a switch and a router.

Answer 11

A switch knows the destination address but not how to get there

Question 12

What data is in a packet?

Answer 12

The header, Payload and trailer

Question 13

How big is a typical packet?

Answer 13

between 500 and 1500 bytes

Question 14

What does the header on a packet contain?

Answer 14

Senders IP
Recipients IP
Protocol
Packet number
Time to live (hop limit)

Question 15

What is contained in the trailer of a packet?

Answer 15

Error checking components to maintain the payload integrity
Techniques to check the data by the receiving host (CRCs)

Question 16

When is the checksum calculated during file transfer?

Answer 16

When the packet reaches it’s destination

Question 17

What happens if the checksums after file transfer do not match?

Answer 17

The data is corrupted and rejected so new data is requested.

Question 18

Why does TCP and other protocols exist?

Answer 18

So data is handled the same way in every computer

Question 19

What is a gateway in a network?

Answer 19

A gateway is a physical appliance that removes the headers from packets and reapplies them with the correct format for that network.

Question 20

What are the 4 stages of the TCP/IP process?

Answer 20

Application
Transport
Internet
Link

Question 21

What happens at the application layer of TCP/IP?

Answer 21

The application layer provides the services for application that want to access the internet such as the protocol to be used

Question 22

What happens at the transport layer of TCP/IP?

Answer 22

Uses TCP to establish an end to end connection while it splits data into packets and numbers them. IT also adds a port number to be used based on HTTP protocol.

Question 23

What happens at the internet layer of the TCP/IP process?

Answer 23

Gives every packet a source and destination IP address

Question 24

What happens at the link layer of the TCP/IP process?

Answer 24

The link layer operates the physical connection between the computers and attaches the MAC address of the physical NIC that packets should be sent to

Question 25

What does the Link layer do upon receiving data?

Answer 25

Removes the MAC addresses and gives the packets to the internet layer

Question 26

What does the Internet layer do upon receiving data?

Answer 26

Removes the IP addresses from the packets and passes the data to the transport layer

Question 27

What does the Transport layer do upon receiving data?

Answer 27

Removes the port number from all the packets and reassembles the packets into the correct order before passing to the application layer.

Question 28

What does the Application layer do upon receiving data?

Answer 28

Takes the data and presents it in a browser.

Question 29

What are port numbers?

Answer 29

Numbers that represent the protocols with which data is being transferred

Question 30

What protocols does sending and receiving emails use?

Answer 30

SMTP (sending)
POP3 (viewing and deleting after download)
IMAP (viewing emails while saving a copy on the server)

Question 31

What is a firewall?

Answer 31

Hardware or software that controls access to and from a network.

Question 32

How does a firewall work?

Answer 32

It opens and closes ports within the firewall to only allow certain traffic through.

Question 33

What is packet filtering?

Answer 33

When packets are inspected by the firewall to check which port they are trying to access

Question 34

What is a proxy server?

Answer 34

A proxy is a server that you can connect to which hides your IP address by sending requests to the web server on your behalf.

Question 35

What are the functions of a proxy server?

Answer 35

Enables mostly anonymous surfing
Filters undesirable online content
Logs user data and requests
Provides a cache of previously visited sites.

Question 36

What is a worm?

Answer 36

A malicious program that self-replicates without needing to be run

Question 37

What is a trojan?

Answer 37

A malicious program that pretends to be something else

Question 38

What is phishing?

Answer 38

When people attempt to manipulate a victim into visiting fake websites and giving away personal information.

Question 39

What improvements could be made to code quality to aid against threats?

Answer 39

Guarding against buffer overflow attacks
Guarding against SQL injections
Use of strong passwords
Two-factor authentication
Use of access rights (permissions)