Networks

Question 1

What is a computer network

Answer 1

Two or more computers connected together so that they can communicate

Question 2

What is a LAN

Answer 2

Local area network

Covers a small geographical area such as a single site building e.g school

Question 3

What is a MAN

Answer 3

Metropolitan Area Network
Covers a highly populated area such as a town or city
Technology such as fiber optic and wireless

Question 4

What is a WAN

Answer 4

Wide area network
Covers a large geographical area such as a country or globally e.g bank c2k
Technology such as telecoms ie underwater fiber optics mobile networks satellites etc

Question 5

What is a Network Interface controller (nic)

Answer 5

Every node on a network needs a NIC

Provides a our for cable to plug in or wireless protocol (WiFi)

Question 6

What is a media converter

Answer 6

Transforms the signal from one media type to another e.g Turing a hdmi signal into a usb or Ethernet to fiber optic

Question 7

What is a Wireless Acces point (WAP)

Answer 7

Connection point for multiple devices on a network

Turns WiFi protocol domhnall to Ethernet and vice versa

Question 8

What is a switched huh (switch)

Answer 8

Central Connection point
Bring multiple nodes together
Manages data traffic on network 
Passed data packets to the distinction node
Using Mac addresses 
Address table

Question 9

What is a repeater

Answer 9

Voltage drops over long distance
Resistance in copper cables
Eventually it is not understood by system
Repeated reconstructs the original signal and forwards it on
May need multiple repeaters over very long distances

Question 10

What is a file server

Answer 10

Allows users to log in 
Security such as access rights
Store all users files
Manage and share network resources
Print server
Proxy server
Email server

Question 11

What is a MAC address

Answer 11

12 hex digits
Every network or communication interface card has a unique MAC address assigned by manufacturer when created
Permanent cannot change
Used for LAN addressing

Question 12

What is an IP Address

Answer 12

4 denary numbers know as octets
IP addresses are assigned by DHCP server when device connects
Used for internet addressing
Every computer on internet has a unique IP address

Question 13

How is an IP address assigned??

Answer 13

DYNAMIC 
An IP address will be assigned to a device each time it connects to a network 
From a pool of available addresses
Within network range 
Can be different each time 

STATIC
An IP address is assigned the first time it connects
Same address is reserved for this device
Every time it’s connected
But the static address can be changed

Question 14

Compare Sever Based Network and a Peer to Peer Network

Answer 14

Server Based Network
One controlling computer on the network
.. Accepts request for services e.g. files, printing etc
.. Mist provide those services (allowed by security)
Centralized control
Lots of maintenance takes from one location
Backups
Security
Installing software

Peer to Peer Network
All computers are equal
Computers are both consumers of and provides of services e’g sharing files
Computers do not have to provide services e.cpu is busy
Each node make some resources available eg cpu files
Need to make changes to every individual computer e.g. security settings, installing new software updates backups etc.

Question 15

What is a bus topology

Answer 15

It is when 1 communication line is shared
…Data is transmitted in all directions on bus
… Data is seen by lo nodes
Which is ignored by all except the addressed node
Uses CSMR

Question 16

What is a ring topology

Answer 16

Each node has links to 2 other nodes in loop
Data moves in one direction around the ring
..using token passing
Possible that I have 2/dual ring network
Passes from node to node until it reaches final destination

Question 17

What is a star topology

Answer 17

Every Computer has a dedicated communication link back to server
…All data is sent to central point and then forwarded to connect node

Question 18

Compare the three topology regarding Adding new nodes

Answer 18

Bus: power down network… cut cabling and bus, to insert a t connector and plug in a node

Ring: remove 1 cable link it to a new node and add cable from new node to next node

Star: plug node into port if available
If not add a hub and plug into that

Question 19

Compare the three topology regarding cost

Answer 19

Bus: Cheaper because it is just one cable

Ring: cheap (not as cheep then bus) need more ports cables and network cards

Star: very expensive each node has cable going all way back to server

Question 20

Compare the three topology regarding speed

Answer 20

Bus: slowest
1 data line, 1 packets can be transmitted at a time
A lot of problems as network grows
Many more controllers and bottle necks

Ring: Deal with more nodes than a bus with less disruption to speeds
…Especially with dual ring
…No collisions
…up to a certain point

Star: Fastest no collision as they all have dedicated lines
Every node could be sending simultaneously

Question 21

Compare the three topology regarding security

Answer 21

Bus: least secure
All nodes hear all message

Ring: not that secure
Messages are passed through various nodes

Star: most secure as messages passed only to the addresses node

Question 22

Compare the three topology regarding increasing the number of nodes

Answer 22

Bus: Doesn’t scale well
Too many nodes = too much traffic
Won’t be able to come

Ring: Scale better than bus
Multiple communication simultaneously
Reaches a point where too much traffic on network
Improved if dual ring

Star: Easy to scale
Every computer has own communication line
Extended star (segment network)

Question 23

Compare the three topology regarding robustness

Answer 23

Bus: single cable failure and no network - not very robust

Ring: one or two failures bring down network

Star: very robust, cable failure only affects node connected to it
,,, central hub is it weak point

Question 24

What is Bandwidth

Answer 24

Bandwidth is a value that refers to the maximum amount of data that is transferrable across a given medium in a given period of time

Question 25

What is Broadband

Answer 25

It is a higher transmission rate (bandwidth) | Higher than dial-up (54 kbps) or ISDN (128Kbps)

Question 26

What is the Ethernet

Answer 26

Set of protocols for hardware and communications Hardware e.g. coaxial cable Twisted Pair

Question 27

What is a Twisted Pair

Answer 27

8 Cables in 4 pairs That are colour coded They are twisted in pairs all together which provides with some shielding properties It can have additional outer shielding for noisy environments of electromagnetic radiation e.g. Cat 5, Cat 6, Cat 6E More twisting = More copper - Added Shielding = Greater Bandwidth - Higher Price

Question 28

What is Fibre Optics

Answer 28

Light travelling along glass fibre (cable) Total Internal Reflection ...No loss of light (signal) ...Huge distances without the need for repeaters ...The light beam reflects off internal surface/edge of glass fibres Multi-Mode Fibre More than one light sensor simultaneously on the same fibre optic strand at different light frequencies with multiplying speeds I.E. Even Higher Speed

Question 29

What is WiFi

Answer 29

``` Wireless Fidelity Used Radio signals to encode data Different protocols within standards (802.22)# e.g. b,n, ac etc.. Rates from 54 Mbps to 600 Mbps 24 GHz range (also 5 GHz Range) 11 Wifi Channels in range ```

Question 30

Compare the three technologies (WiFi, Ethernet and Fibre Optic) in terms of security

Answer 30

WiFi - Transmitted Over Air - Transmitted everywhere in range (Problem - So it must be encrypted Ethernet -Data on cables -Need Physical Access (better than wifi) - Could be located inside walls or underground -If physical access ... Tap by using Electromagnetic Radiation ... or by using a physical connector with copper Fibre Optic -Data on cables - Need Physical Access If accessed -No electromagnetic radiation, light is totally internal (better than ethernet) - Cannot cut into a Fibre Optic cable without destroying it

Question 31

Compare the three technologies (WiFi, Ethernet and Fibre Optic) in terms of Bandwidth

Answer 31

Wifi -Slowest -Shared Channels (1 per aerial) -If there are 5 channels, some channels must be shared -Lead to collisions (requires data to be resent) Radio is slower than electrical signals Ethernet - Each computer has own cable (Better than Wifi) - Ethernet has a higher bandwidth than wifi Fibre Optic - Speed of light - No loss of signal - Large distances, no need for booster/repeater - V.High bandwidth

Question 32

How does Error Checking work

Answer 32

-First Node transmits the message to the receiving mode -The receiving node transmits the same message back - The first node compares what is sent to what it received back ... If the message matched = There was no error ... If the message did not match = Error Detection

Question 33

How does Parity Checking work

Answer 33

There are two forms of Parity check, Odd or Even - It is used to check a chunk of data e.g.byte - The least significant bit is used as a parity check digit - The Odd number = Odd number of 1s and 0s (10010100) (3 x 1s) (5x0s) - The Even number = Even Number of 1s and 0s (10010101) (4 x 0s) (4x1s) - transmitting device sends data, it counts the number of set bits in each group of seven bits. - if the number of set bits is even, it sets the parity bit to 0 - if the number of set bits is odd, it sets the parity bit to 1. In this way, every byte has an even number of set bits. - On the receiving side, the device checks each byte to make sure that it has an even or odd number of set bits. If it finds an odd or even number (opposite one) of set bits, the receiver knows there was an error during transmission

Question 34

What is the problem with parity check

Answer 34

It detects bits that have been flipped 0-1 1-0 | It cannot detect an even number of flips

Question 35

What is check sum and how does it work

Answer 35

-Same as any other check digits | Except the calculated value may be longer than 1 digit

Question 36

What is error correction

Answer 36

If an error is detected by echo checking, parity checking or checksum, we still need the correct data to be transmitted The simplest form of connection is RESENDING Going through the same process again

Question 37

What is a checksum and how does it work

Answer 37

Checksums involve counting the number of 1 BIT’s in a packet and sending this as a mathematical total at the end of the packet. The process involves the data packet ‘checking itself’ at the destination looking for errors; if errors are found the data will be transmitted again

Question 38

What is a Cyclic Redundancy Checks

Answer 38

Cyclic Redundancy Check (CRC) is an error detection mechanism in which a special number is appended to a block of data in order to detect any changes introduced during storage (or transmission). - It detects and corrects errors automatically - The checksum is added to the chunks of data before transmission - Forward Error Checking uses longitudinal and latitudinal parity checks - The CRC is recalculated on retrieval (or reception) and compared to the value originally transmitted