Networks

Question 1

Network

Answer 1

Set of interconnected devices that exchange data and resources with each other

Question 2

Internet

Answer 2

The largest public network (WAN), a network of interconnected networks. Contains a backbone, and a set of dedicated connections that connect large networks at various points in the world. Each point is connected to another regional network controlled by ISP’s.

Question 3

WiFi

Answer 3

Wireless networking tech providing high speed internet and network connection. A family of wireless network protocols.

Question 4

Station

Answer 4

Consists of NIC and computer

Question 5

Wireless Access Point

Answer 5

Point where devices connect to a wireless network. Requires connection to a router.

Question 6

Network switch

Answer 6

Connects devices on a LAN, receives and sends packets.

Question 7

IP Address

Answer 7

A unique identifier for every device on the internet. Made up of 4 or 6 octet values.

Question 8

URL

Answer 8

Used to specify the means of accessing a resource across a network and its location. Consists of protocol and domain name

Question 9

Web search procedure

Answer 9

DNS server maps domain to an IP address.
If it cannot resolve, it passes the request to the root DNS.
DNS server sends the IP address to the requested web browser.

Question 10

DNS servers

Answer 10

Domain Name system; dedicated computers with an index of domain names and their IP addresses.
When computers query a DNS server to domain, it returns an IP address for the computer to send a message to it.

Question 11

Topology

Answer 11

Arrangement of devices that make up a network

Question 12

Bus topology

Answer 12

Devices connected by a single cable(backbone).
Devices can be easily added, good for small networks.

Unidirectional,only one computer can transmit at a time,main cable is point of failure, performance lowers with heavy use due to collisions, poor security.

Question 13

Star Topology

Answer 13

Contains central hub which acts as connection point for devices. Computers connected to central node. Switch communicates to specific computer intended.

Good performance, easy to isolate problems, more secure

Expensive to set up, central device is point of failure.

Question 14

Physical vs logical topology

Answer 14

Physical: Defines how devices are physically connected
Logical: Defines how devices communicate across physical topology

Question 15

5 internet global registries

Answer 15

Allocate IP addresses to specific domain names, which must be unique.

Question 16

Protocols

Answer 16

Set of rules that define how data is transmitted across a network (i.e TCP/IP stack)

Must be standard across all devices for communication to work

Question 17

TCP/IP stack

Answer 17

Transmission control protocol/internet protocol consists of 4 layers:
Application
Transport
Internet
Link

Question 18

Application layer

Answer 18

Provides services for applications that want to communicate across a network. Uses high level protocols like SMTP, FTP,HTTP that set an agreed standard between end points.

Presents image data for user at destination

Question 19

Transport layer

Answer 19

Uses the TCP to establish end to end connection with receiver. Splits data into packets, numbers them sequentially, adds port number to be used based on HTTP. At receiving end, confirms if packets have been received, requests for missing packets to be resent.

Question 20

Internet layer

Answer 20

Uses the IP to address packet with source and destination IP address. Router forwards each packet to an endpoint, defined by combination of IP addresses and port numbers. Router uses routing table to instruct next hop

Question 21

Link Layer

Answer 21

Operates across a physical connection. Adds MAC address of physical NIC that packets should be sent to.

Question 22

FTP, SMTP, IMAP,POP3

Answer 22

FTP - used to transfer files
SMTP - send and receive emails
IMAP- manages emails
POP3- downloads emails

Question 23

Firewalls

Answer 23

Hardware/software that controls access to and from a network. Ports are opened to allow specific traffic (packets) to pass

Question 24

Packet filtering

Answer 24

Packets inspected by a firewall to see which port they are trying to access, if allowed through, port opened for duration of communication, otherwise firewall rejects.

Question 25

Proxy servers

Answer 25

Make a web request on behalf of users device, hiding true request’s IP address from receiver.
Enables anonymous surfing, can be used to filter undesirable online content, logs user data with their requests. Provides a cache of previously visited sites to speed access.

Question 26

Phishing

Answer 26

Using fake emails to manipulate victims into visiting a fake website to give away personal information.
Measures:
2fa,strong passwords, use of access rights, guard against SQL injection and buffer overflow, improving code quality.

Question 27

Malware

Answer 27

Malicious software, annoys users and damages their data.
Examples: trojans, viruses, worms

Question 28

Virus

Answer 28

Infects other programs ans data by self replicating. Need a user to spread

Question 29

Worms

Answer 29

Do not need a user to spread

Question 30

Trojans

Answer 30

Pretends to be harmless application. Cannot self replicate.

Question 31

Gateways

Answer 31

Alternative to routers.
Required when data is travelling from one network to another that use different protocols.
Required by networks using different transmission media.
Header data removed and reapplied using correct format of new network.
Can combine with router to create one integrated device.

Question 32

Routers

Answer 32

Forward data packets from one network to another
Shares data about available routes to destination
Looks up destination IP address in routing table to find best router to forward packets to,
Each transfer between routers=hop.

Question 33

Data packets

Answer 33

A segment of data that needs to be sent (size ~ 500-1500 bytes)
Kept small to ensure individual packets do not take time to transfer preventing other packets from moving.
Should not be too small as additional data makes transfer inefficient.

Question 34

Data packet format

Answer 34

Header- holds sender and receivers ip address, time to live/hop limit
Payload - holds data and protocol used as well as packet number
Trailer - Contains a checksum/CRC to detect transmission error. (done by obtaining a hash total calculated by adding number of 1’s in transmission)

Question 35

Packet switching

Answer 35

Packets sent across separate routes, determined by least congested route. Easily reassemble when reaching receiver. Packets that do not make it are resent.

Question 36

Circuit switching

Answer 36

Creates direct link between devices for duration of communication, even when data is not transmitted (a waste of bandwidth)
Very device specific as two devices need to transmit and receive at the same time.
Data segments are sent in order of arrival so simplification of restructuring packets at the receiving end.
Switches connecting and disconnecting circuits causes electrical interference, producing corrupt data.