communication systems Flashcards
1
Q
communication systems
A
systems enabling users to send and receive data and information
2
Q
framework of communicaiton systems (7)
A
message/transmission medium
source/destination
switches and routers
three levels of protocols
transmitter/receiver
users/participants
node
3
Q
message/transmission medium
A
data packets and the hardware through which they travel
4
Q
source/destination
A
application where the message is created/ends up
5
Q
swtiches and routers
A
where addresses are attached and read so that data packets are sent on the most suitable path to get to their destination
6
Q
three levels of protocols
A
where packets of data are encoded/decoded to or from a suitable form for transmission
7
Q
transmitter/receiver
A
where signals are generated or received
e.g. MIC or modem
8
Q
users/participants
A
people involved in using system
9
Q
node
A
each device on a network
10
Q
functions which happen as messages are passed between source and destination (8)
A
message creation
organisation of packets at the interface between source and transmitter
signal generation by the transmitter transmission
synchronising the exchange and routing
error detection and correction
security and management
transmission
addressing and routing
11
Q
addressing and routing
A
data packets pass through many different and varied links during transmission
12
Q
each communication link
A
has its own protocol
13
Q
it is likely that differen data packets from same file will
A
travel on different pathways through journey
14
Q
message creation
A
message is compiled at source on preperation for sending
takes place using software application
participant types message into application such as web browser
15
Q
organisation of packets at the interface between source and transmitter
A
as message descend layers of protocoles data packets are wrapped in header and trailer of appropriate protocol
multiple headers and trailers on each packet
16
Q
at control level protocols are managed by
A
operating system
17
Q
protocols ensure
A
packets reach destination correctly
18
Q
transmitter
A
physical hardware that encodes data onto medium creating signal
19
Q
transmitters are receivers are contained
A
in same hardware device
20
Q
hardware is controlled by
A
protocols at transmission level
21
Q
signal generation by transmitter transmission
A
done by hardware such as NIC or modem
changes computer’s binary data into seried of physical signals
22
Q
how is transmission perfectly synchronised
A
transmitter and receiver use common clock
23
Q
synchronous communication transfers
A
large packets of data
24
Q
sychronising the exchange and routing
A
transmitter encodes signal as receiver decodes
series of bits included in message and start and embedded between packets
clocks of sender and receiver are working in phase with each other
25
error detection and correction
as messages descend level prior to transmission protocols calculate checksum and crc values and include them within header or trailer
26
if error is detected by error check calculator
that packet is discarded and replacement packet sent
27
error checking methods (3)
parity check
checksum
cyclic redundancy check
28
parity check
determines whether number of ones and zeroes is odd or even using additional bit called parity bit
29
problem with parity bit check
if 2 bits are swapped then there can be an error that is not identified
30
checksum
counts up number of 1s in transmission and adds number as an extra byte into transmission of each packet and is compared at the end of each packets transmission
31
problem with checksum
the numbers can be in the wrong places and be called successful
32
cyclic redundancy check
more accurate than parity checking and checksum
treat message as enormous binary number and divide by a fixed binary number
upon receival divide it again and compare remainders
33
security and management
many protocols restrict messages based on usernames and passwords and others encrypt messages during transmission
some messages are ptotected by need for password
other messages use a secure protocol (https) that encrypts data being sent
34
transmission
occurs as signal travel trhough medium
each bit or pattern of bits moves from sender to receiver as a particular waveform
35
protocol
formal set of rules and procedures that must be observed for two devices to transfer data efficiently and successfully
36
seven-layer model for open ysstems interconnection
international standards organisation developed a set of standard for transfer of data
37
open systems interconnection model layers
caps - ipt levels
APPLICATION
application
presentaiton
COMMUNICAITON AND CONTROL
session
transport
network
TRANSMISSION
data link
physical
38
handshaking
process of negotiatinf and establishing rules of communication between two or more devices
before devices communicate they handshake to agree on protocol that will be used
39
why is handshaking important
different types of computers and devices can communicate effectively with each other over different types of transmission media
40
handshaking includes (3)
format od data packets or frames to be transferred
error checking methods used
speed of data transfer
41
functions performed by protocols at different levels
protocols in eahc layer will rpocess message and pass it onto the next layer in the stack
at receiving end processes occur in reverse order so that receiver can understand message
42
intelligent agents
programs that run in the background to complete tasks that assist people
also known as daemons or bots
43
types of intelligent agents (4)
autonomous
proactive
responsive
adaptive
44
autonoumous intelligent agents
operate independetly without constant guidance form users
make decisions to determine how to solve problesm and solve them on their own
45
proactive intelligent agents
intelligent agents do not wait to be told, rather they act and often make suggestions to the user
46
responsive intelligent agents
intelligent agents recognise changes in their environment that indicate changes in user needs and they alter their behaviour accordingly
47
adaptive intelligent agents
change their behaviour or learn new behaviour over time to account for changing user preferences
48
examples of intelligent agents
monitoring website changes
enhancing reuslts returned by search engines
finding best prices and products
checking documents for plagerism
air traffic control systems
medical monitoring systems
49
olap
online analytical processing
technique for providing business decision makers with statistical evidence
used with data mining
50
oltp
online transaction processing
databases allow transactions to be processed immediately by remote users
51
server
provide specific processing services for clients
52
advantage of client-server model
many different users can have access to up-to-date data and can access it from many different computers
53
disadvantage of client-derver model
clients may not have remote access to the server and will need to carry allf iels onto local hard drive
54
client-server model
agreed protocol between client and server
they work and process independently but agree on how things are done
55
clients
request service, and wat for a response while the server processes this request
56
2 types of computers present on network
client
server
57
each server
provides service to multiple clients
58
client-serber processing
a form of distributed processing
ifferent computers are used to perform the specific information processe snecessary to acviene the system's purpose
59
client-server processing occurs
sequentially
client is processing or server is processing but not at the same time
60
client applications
privde user interface and therefore they manage all interactions with end-users
61
examples of servers
database servers
network servers
web servers
print servers
file servers
62
network servers
control authentication of users to ensure security
63
virtual server
able to be used for different taks and processes depending on the needs of the network
64
server may be dedicated service
it has been assigned a role such as file server and that is the only thing it is able ot do
65
thin client
only perform basic processing tasks such as receivng data displaying it on the screen and also transmitting input back to server
66
thick clients
has a large amount of software and can perform its own processing as required
67
voice over internet protocol
technology that allows you to make voice calls using broadband internet connection instead of an analog phone line
68
wired transmission (3)
twisted pair
coaxial cable
optic fibre
69
twisted pair
pairs of insulated copper wires
twisting reduces inference from noise caused by electromagnetic, power or electrical sources
most common and cheapest cable
slower than other cables
only functional over short distances
70
lan
local area network
conneect devices over a small physical distance
71
wan
wide area network
network that connects devices over large physical distances
72
nic
network interface cards
needed for devices to communicate with each other
expansion cards that slot into motherboard and connect to network with cable
73
hub
connecting device
connect nodes together into a network
74
simple hubs
accept transmission trhough one cable and pass transmission to any devices connected to hub through other cables (broadcats signal)
75
switches
signals are switched and transmitted to intended receiver
most hubs have been phased out for switches
76
bridges
connect 2 lans that use same communication protocols together
e.g. business spread over multiple floors
77
gateways
connects two networks together
can connect networks using different communication protocols
connect lan to internet
78
routers
direct traffic on network
direct messages over most efficient path to destination
79
modems
used to connect network or individual computer to internet
most are combined with routers
80
coaxial cable
thick core of copper wire currounded by insulating material
better shielded form interference than twisted pair
thicker and less flexible than twisted pair
more expensive than twisted pair but faster at transmitting data
81
fibre optic cable
made up of thin strandsof glass fibre
most expensive
able to support faster transmission rates over greater distances
82
wireless transmission
use atmosphere as a medium to carry electromagnetic waves between models
allow nodes to move freely within coverage area
83
types of wireless transmission
microwave
satellite
mobile phone technology
bluetooth
infrared
wireless lans and wifi
84
microwave
have to be within line of sight
40 to 50 km of each other
point-to-point terrestiral microwave (towers on the ground that transmit)
85
satellite
use microwaves to transmit data
86
mobile phones
each entwork is divided into a cell that has its own base station or mobile phone tower
87
bluetooth
communication system for stort-range transmission
87
communication protocols (2)
application level protocols
transmission level protocols
87
infrared
waves occur above microwaves and below visible light
travel in striaght line
short distances
88
types of application level protocols (4)
http
smtp
SSL
ftp
89
application level protocols
actual data to be transmitted is creted by software application
90
http
hypertext transfer protocol
used by web browers to communicate and retrieve web pages from web servers
establish connection with html server
91
smtp
simple mail tranfer protocol
used to send and receive emails
allow connection to email server
92
SSL
secure sockets layer
used to transmit data securely over internet
used when s is after http
for e-commerce
uses encryption methods and digital certificates
93
transmission level protocols
layer that defines how transmission medie is shared
device drivers control physical transmission hardware and determines size of transmitted packets and speed of transfer
perfoms physical transfer
94
types of transmission level protocols (2)
ethernet
token ring
95
ethernel
built into hardware deivces that transmit and receive data
used for lans
forms frames to contain data packet
synchronises clocks
decides speed of transmission
96
token ring
not used often today
receives and transmits data packets to next node on ring network
97
communication control and addressing level
where communication with network is stablished and maintained
98
TCP
transmission control protocol
error checking and data flow control
ensures messages are actually delivered correctly
99
IP
internet protocol
routes data packets over mot efficient pathway for destination
uses IP address
100
types of network topologies (4)
star
bus
ring
hybrid
101
network topologies
topology of network described way in which modes are connected and also how data is logicall transferred between nodes
102
physical topology
actual way devices are connected together
103
logical topology
way in which data travels around network
104
bus topology
common cable called buss connects all nodes
all nodes receive data transmitted but only node to which it is addressed acccepts and processes data
not suitable for busy networks with many nodes
little cabling
problems when two nodes attempt to send at same time as frames collide
105
backbone
line connecting nodes
106
terminator
end of topology
107
t-connector
connects nodes to backbone
108
media access control
bus topology
prevents collisions or deals with collisions after
109
ring topology
nodes are connected to a close loop so each station on network is physically occnnected to two other devices
data packets circulate ring in one direction
each node received and transmits
110
disadvantages fo ring topology
fault in cable affects whole network
all nodes need to be powered up
111
token ring protocol
ring topology
token continuall circulates network
112
star topology
nodes are attached to central point (usually switch) via own dedicated cable
most lans use this
113
disadvantages of star topology
more cabling
if switch is faulty all nodes are affected
114
hybrid/tree topology
combinaiton of bus, star and ring topologies
backbone of optic fibre foring bus or ring
allows for expansion of network
115
mesh topology
more than one physical path between nodes
primary topology of internet
excellent fault tolerance
116
wireless network topology
wireless access point provides signal to devices on network
devices join network with password
117
computer need to work with
digital data
118
ADC
analog to digital convertoer
takes samples of analog wave every frantion of a second
meausres strength of signal and produces series of digital numbers to records value
119
DAC
digital to analog convertor
average out a series of digital values to produce smoothly marrying waveform
120
network administrators
carr out various tasks involved in administration of network hardware and software
121
network administration tasks
Adding/removing users
Assigning users to printers
Giving users file access rights
Installation of software and sharing with users
Client installation and protocol assignment
Logon and logoff procedures
Network-based applications
