communication and networking Flashcards
Serial transmission
Data flows through a signal line
Parallel transmission
Data flows through multiple lines
Why serial transmission is better than parallel
Cheaper as less wire is required
bandwidth is higher
Synchronous data transmission
Where the pulse of the clock of the sending and receiving devices are in time with each other. They might share a common clock
Asynchronous data transmission
Data is transmitted between two devices that do not share a common clock signal
compare synchronous with asynchronous data transmission
Asynchronous: Receiver and transmitter are not synchronised by a common clock
Synchronous: Receiver and transmitter continuously synchronised by a common clock
purpose of start and stop bits in asynchronous data transmission.
Indicates to the receiving device when the data transmission begins and ends
baud rate
Number of signal changes in the medium in a second
Bandwidth
Range of frequencies that can be transmitted across a network connection
Bit rate
Number of bits transferred between devices in one second
latency
rate at which signals on a wire change
protocol
Set of rules
Differentiate between baud rate and bit rate.
Bit rate can be higher than baud rate if more than one bit is encoded in each signal change.
relationship between bit rate and bandwidth.
Bit rate is directly proportionate to bandwidth.
Physical star topology
How nodes are physically laid out
Logical star topology
How data flows through a network
How can a network physically wired in a star topology behave logically as a bus network
By using a bus protocol and appropriate physical switching
pros and cons for peer to peer and where it might be used
Doesn’t need a central server and easier to set up as no server to configure and cheap as there is no need for server
Less secure and speed of one machine can affect other machines in a network
file sharing
pros and cons for peer client server
Faster access speed and more secure
Client is dependant on the server
web apllications, emails
peer to peer
each computer has equal status
resources stored on or shared from any computer
no reliance on central server
client server
most computers are nominated as clients and one or more as servers
client access resources from server
reliance on central server
Explain the purpose of WiFi.
A wireless local area network that is based on international standards.
Used to enable devices to connect to a network wirelessly
components required for wireless networking.
Wireless network adapter.
Wireless access point.
how wireless networks are secured
Strong encryption of transmitted data using WPA/WPA2, SSID broadcast disabled, MAC address white list.
explain the wireless protocol Carrier Sense Multiple Access with Collision Avoidance
computer with data to send monitors/listens for (data signal)
if (data) signal present transmission in progress then continue to wait
when no (data) signal present computer sends a Request to Send / RTS
two computers could start transmitting simultaneously if they both detect there is no data signal
receiver responds (to RTS) with a Clear to Send signal
RTS/CTS signal blocks any other transmissions from nodes in range
when CTS received then start to transmit
if CTS not received continue to wait
receiver sends acknowledgement after (all) data received
purpose of Service Set Identifier (SSID)
to identify a specific wireless network
operation of ssid
data is stored electronically
data is stored in floating gate transistors
data is organised into blocks
a block must be erased before it can be overwritten
structure of internet
application layer:
Selects and uses the correct protocol to transmit data
transport layer:
an end to end connection between the sender and the receiver. The layer then splits the transmission into packets.
network layer:
Provides the correct IP addresses for each packet’s source and destination
link layer:
Controls physical connections between pieces of hardware in a network. Adds MAC addresses to packets which it receives from the network layer. The MAC addresses identify the hardware to which a packet should be sent
main components of a packet
header: contains information about the packet (origin and destination ip adress)
payload: actual data
router and its use
device used to direct packets being transmitted between networks
used in local area networks
gateway and its use
device that allows data to flow from one network to another
Connecting a LAN to the internet
Compare and contrast thin-client computing with thick-client computing
processing is carried out
clients are cheaper to purchase
workstations need less maintaining
Compare JSON (Java script object notation) with XML
easier for a human to read
more compact
easier to create
easier for computers to parse and therefore quicker to parse
