communication Flashcards
1
Q
WAN (wide area network)
A
- network that connects devices within a larger geographical area
- private or public ownership
- transmission medium: PSTN or satellite link
- lower data transfer rate
- higher congestion
2
Q
thin client
A
- runs solely on the resources provided by the server and has no local storage
- only provides input and receives output; processing done by server
- less expensive
- secure, cannot run unauthorized software
3
Q
thick client
A
- independent, does not require the server to run
- processes most of the application
- can function offline
- no lag related to network problems
4
Q
server
A
a computer or system that provides resources & data to other computers called clients
e.g: file server, print server, proxy server, web server, application server
5
Q
pros of client server
A
- files and resources are centralised
- management of security
- centralised back up
- internet monitoring
6
Q
client server applications
A
- printer
- file sharing
- proxy server
- email server
- database server
- domain controller server: management of user accounts (IDs & pswrds)
7
Q
peer-to-peer model
A
- all computers are of equal status
- computers can communicate and share resources
- each computer is responsible for its own security
- lesser initial setup cost
- can work even if a device goes down
8
Q
benefits of peer to peer
A
- parts are available from more than one host
- allows users to download different parts of files separately
- avoids possibility of congestion when more clients are simultaneously requesting to download a file
9
Q
networking advantages
A
- file sharing
- software sharing
- hardware sharing
- higher storage
10
Q
networking
A
the exchange of info and ideas among people with a common profession or special interest
11
Q
network
A
two or more systems connected through wired or wireless means
12
Q
LAN (local area network)
A
- network that connects devices within a small geographical area
- only private ownership
- transmission medium: twisted pair cable, coaxial cable or wi-fi
- higher data transfer rate
- lesser congestion
13
Q
internet
A
a global network providing communication facilities
14
Q
drawbacks of peer to peer
A
- reduced security, each computer is at risk from viruses from another computer
- no central management of backup, if the data from one computer is not backed up, it is lost to all of them
- no central management of file, consistency is difficult to maintain
- individual computers may respond slower because they are being accessed by other computers
15
Q
bus topology: how packets are transmitted
A
- packets has address of recpient
- sender transmits data through the bus
- the bus carries data along the central cable
- as the data arrives at each computer, the system compares the address to see if it matches
16
Q
bus topology disadvantages
A
- if the main cable breaks, the entire network goes down
- difficult to detect and troubleshoot fault at an individual station
- efficiency reduces as the number of devices connected increases
- collisions, not suitable for network with heavy traffic
- security is lower because several computers receive the sent signal from the source
17
Q
bus topology advantages
A
- easier to setup/extend
- less cable required
- less expensive
18
Q
bus topology
A
- uses a single central cable to which all computers and devices are connected
- used when small and temporary network is needed, e.g: offices and schools
- used for networks that dont rely on high data transfer speed
19
Q
star topology
A
- must have a central server that all devices are connected to
- each node has a dedicated connection
- each connection must be bi-directional
- used when high performance is needed
- found in homes where router acts as server, educational establishments, large organisations
20
Q
advantages of star topology
A
- signals only go to destinations (secure)
- easy to connect/remove nodes
- centralised management helps in monitoring the network
- failure of one node or link doesn’t affect the rest of the network
- fewer collisions
21
Q
disadvantages of star topology
A
- if the central device fails then whole network goes down
- performance is dependent on capacity of central device
22
Q
star topology: how packets are transmitted
A
- packets have address of recipients
- sender sends data to central devices
- server reads address and finds where recipient is
- server directly sends data recipient
- server transmits packets only to recipient
23
Q
mesh topology
A
all devices are interconnected with each other
- routing: gives nodes routing logic so data can be directed to its destination via the shortest route
- flooding: just sends data via nodes without routing logic
- used in establishments where communication is important, e.g: military organisations, emergency services
24
Q
advantages of mesh topology
A
- any broken links in the network don’t affect other nodes
- good privacy and security
- easy to expand
25
Q
disadvantages of mesh topology
A
- lot of cabling is needed (expensive and time consuming)
- set up and maintenance is complex
26
Q
mesh topology: how are packets transmitted
A
- packets have address of recipients
- sender transmit packets directly to node; each node is connected to at least one other node
27
Q
mesh topology: how are packets transmitted
A
- packets have address of recipients
- sender transmit packets directly to node; each node is connected to at least one other node
28
Q
hybrid topology
A
- combination of two or more topologies
- used in large organisations with different topologies in each building
29
Q
cloud computing
A
refers to data and applications being stored and run on cloud so less storage is occupied and less processing is done on a local device
30
Q
advantages of cloud computing
A
- files stored on the cloud can be accessed at any time from any device
- no need to carry external storage device
- cloud storage can be free
- security can be better
- most cloud server providers have inbuild backup
- data can be easily shared
31
Q
disadvantages of cloud computing
A
- can only access the cloud with internet
- no control over security
- can take a long time to upload/download data
- can be more expensive in the long term
- could be a limit to amount of storage unless paid for
32
Q
private cloud
A
- owned by and only accessed by an organisation
- used by highly regulated industrives and govt agencies
33
Q
public cloud
A
- owned by a cloud service provider
- for general user, grants access to multiple parties
34
Q
pros of cloud computing
A
- less technical knowledge is required and easy to mplement
- flexibility: can be scaled to match organisation’s growth
35
Q
cons of cloud computing
A
- cannot access the data stored on the cloud if there are bandwidth issues
- poor data privacy since there may be data leakage in public clouds
36
Q
World Wide Web (WWW)
A
- collection of web pages stored on websites
- protocols are used to transmit data across the WWW
- web pages are written in HTML
- URLs specify the location of web pages
- stored on website
37
Q
internet
A
- massive open network of networks
- uses TCP/IP protocol, uses IP addresses to identify devices connected to the internet
- access provided by ISP
- communication used: wired, radio and satellite
38
Q
pros of wireless
A
- devices are more mobile
- easier to set up
- additional devices can easily be added
- many different types of devices can be connectd at the same time
39
Q
pros of wireless
A
- devices are more mobile
- easier to set up
- additional devices can easily be added
- many different types of devices can be connectd at the same time
40
Q
cons of wireless
A
- easier to hack
- interference
- signal degrades quickly
41
Q
twisted pair cable
A
- most commonly used in LANs
- lowest data transfer rate
- suffers most from external interference
- cheapst option
- shielded cables are used commercially as it cancels out some interference
42
Q
coaxial cables
A
- most commonly used in MANs and by cable TV companies
- cost is higher than TPC
- offers better transfer rate
- greatest signal attenuation
- less affected by external interference
43
Q
fibre optic cables
A
uses pulses of light rather than electricity to transmit data
44
Q
pros of fibre optic
A
- less interference in the signal
- greater bandwidth -> faster transmission
difficult to hack so more secure - consumes less power
- lighter in weight -> easier to install
45
Q
cons of fibre optic
A
- high installation cost
- trained people are required to maintain and install
- breaks when bend
- uni-directional
- difficult to terminate
46
Q
copper cable pros
A
- low installation cost
- more flexible
- vast knowlege as it has been around for years
- easier to terminate
47
Q
copper cable cons
A
- less bandwidth rate
- needs repeaters (regenerates sent data signal over network before signal weakens)
- higher interference
48
Q
radio waves
A
- electromagnetic waves, can travel over long distances
- used for TV siglans + mobile phone comms
- low frequency so transmits less data at a time, affected by radio stations with similar frequencies
49
Q
microwaves
A
- larger bandwidth, can transfer more data at a time
- used in TV and MRI
50
Q
infrared
A
- electromagnetic waves
- high frequency
- used in TV remotes
51
Q
satellites
A
- easy to interfere
- expensive to set up
- satellites boost signals that need to reach antennas that are unreachable due to the curvature of the earth
52
Q
switch
A
used to connect together a number of devices to form a LAN that directs incoming data packets to a specified destination address only
53
Q
hub
A
hardware used to connect together a number od devices to form a LAN that directs incoming packets to all devices on the network
54
Q
network interface card (NIC)
A
- provides device with a MAC address to uniquely identify it on the network
- allows each individual device to connect to the network
55
Q
wireless network interface card (WNIC)
A
- provides device with a MAC address to uniquely identify it on the network
- allow each individual device to connect to the network wirelessly instead of a cable
- use antenna to communicate with networks via microwaves
56
Q
bridge
A
- connects two LANs which work using the same protocol, which can be two segments of the same network
- stores mac addressed of all devices between both networks
- used to reduce traffic
57
Q
wireless access point (WAP)
A
- allowing devices to connect to the LAN instead of using a cable
- easy to move a device to a different location
58
Q
repeater
A
device used to boost signals
59
Q
router
A
- enables data packets to be routed between different networks
- acts as a default gateway
- can perform rotocol translation
- can move data between networks
60
Q
gateway
A
- same as router except they connect dissimilar networks
61
Q
how a video is sent using bit-streaming
A
- data is compressed before transmitting
- video is transmited continously as a series of bits
- video is hosted on media server
- on download, server sends data to buffer on client’s computer
- buffer stores data from the server
- user’s stream software receives bit stream from the buffer
62
Q
on demand bit streaming
A
- existing digital files converted to encoded bit streaming format
- link for encoded video is placed on website and user clicks on link to view encoded streaming video
- can be paused, rewinded, fast-forwarded and rewatched
63
Q
pros of bit streaming
A
- no need to wait for the whole file to be downloaded
- no need to store large files on user’s computer
- allows on demand playback
- no specialist software is required for playback in browser
64
Q
cons of bit streaming
A
- video lags if internet is slow, if inadequete buffering capacity
- loss of internet means can’t access films
- may require specific software to run the file
- viruses can be downloaded from the websites
65
Q
real time bit streaming
A
- event is captured live with a video camera
- the video camera is connected to a computer
- video signal is vonverted to streaming media file, encoded on the computer
- encoded feed is then uploaded from the computer to the dedicated streaming server
- server sends the live images to all users requesting it as real time video streaming
- cannot be paused
66
Q
bit rate and bit streaming
A
- bit rate determines how quickly the data is sent over the internet to the viewers
- higher the bitrate or broadband speed, the better the quality of bis streaming and there will be no buffering
67
Q
CSMA-CD (carrier sense multiple access - collision detection)
A
- before transmitting the data, a device checks if the channel is busy
- if channel is free the data is sent
- when transmission begins, it listens to the other device
- if there is a collision, transmission is stopped
- both device wait a different random time, then try again
68
Q
functions of CSMA-CD
A
- monitor traffic
- only allow data to be sent when the line is idle
- detects collision on the network
- halts transmissions when a collision occurs
- calculates random wait time
- allows re-transmission after wait time
- collisions are detected due to voltage change
69
Q
modem
A
converts digital data into analogue data which a computer can process -> connects router to the internet
70
Q
PSTN (public switched telephone network)
A
- PSTN consists of many different types of communication line
- data is transmitted in both directions at the same time
- communication passes through different switching centres
- lines always remain active
71
Q
pros of dedicated lines
A
- faster transmission of data
- more consistent transmission speed
- improved security
72
Q
cons of dedicated lines
A
- expensive to setup/maintain
- disruption to the dedicated line would leave no alternative
73
Q
IP address
A
- stands for internet protocol
- used to locate a device on a netowrk - gives each device an identifier
- each address on network is unique
- allows a device to send data to the correct destination
74
Q
public IP addresses
A
- can be reached across the internet
- provided by ISP
- unique
75
Q
private IP addresses
A
- not publicly registered on the internet
- assigned by router
- more secure
- unique within their network but can be duplicated within another
76
Q
static IP addresses
A
- when a computer disconnects and rejoins a network the address does not change
- address is assigned by ISP
77
Q
dynamic IP addresses
A
- each time a computer rejoins a network the address changes
- address is assigned by the network OS
78
Q
subnetting
A
- split a large network into a grouping of smaller network to help minimize traffic
- improving speed and performance
- IP addresses are broken down into 3 parts by partitioning the host ID into subnet ID and host ID
79
Q
IPV4
A
- each IP address should contain 4 numbers
- should be in range 0-255
separated by full stops - address should not be more than 32 bits
- 4 groups
- e.g: 192.168.0.1
80
Q
IPV6
A
- valid hex number
- only one double colon is allowed
- 8 groups
- separate by colon
- each number is 4 hex digit
- needed when no. of IP addresses needed will exceed number available using IPV4
- e.g: 2001:0800:0000:0000:0000:0000:0000:0000
81
Q
domain name service (DNS)
A
- naming system used for computers or resources with and internet connection
- consists of a hierarchy of DNS servers which have a URLs database of their corresponding IP addresses
82
Q
uniform resource locator (URL)
A
- unique reference address for the exact location of an internet resource on the WWW
- e.g: http://cie.org.uk/computerscience.html
http : enables browser to know what protocol is being used to access information in the domain
cie.org.uk : the domain name
computerscience.html : file name which is being viewed
83
Q
how URL is converted to matching IP
A
- URL is parsed to obtain the domain name
- domain name is sent to nearest DNS server
- DNS holds a list of domain name and matching IP
- domain name resolver searches its database for the domain name
- if DNS doesnt find it, request is forwarded to higher level DNS
- if domain name is found IP address is returned
- if not, error message is output
