9 - Fundamentals of Communication and Networking Flashcards
Explain how a thin-client network works.
- Most processing is done by a central server
- The user input is transmitted from the terminal to the server over the network
- Data needed to produce image is transmitted from server to the terminal over the network
- Applications are not installed on thin client workstations
- Operating system is loaded by clients from server at boot
Explain how the use of a thin-client network instead of a traditional rich-client (thick-client) network will affect the selection of the hardware of the system.
- Higher bandwidth network connection required
- Network must use switch not hub
- Slower processor and reduced RAM
- Server must have multiple processors and a lot of RAM
What is Serial Data Transmission?
Data bits are sent in a sequence, one after the other, over a single wire from the source to the destination.
What is Parallel Data Transmission?
Multiple bits are sent simultaneously over multiple parallel wires from the source to the destination.
What is a problem with Parallel Data Transmission?
There is a possibility that data skew may occur as the bits could travel at slightly different speeds over each of the wires.
What are the advantages of serial over parallel data transmission?
- Parallel communication requires more wires and hardware; therefore, serial transmission tends to be cheaper.
- With parallel communication, there is a risk of data skew over long distances, whereas serial is reliable over much longer distances.
- Parallel communication carries the risk of crosstalk between wires which results in more chance of errors. This is largely avoided with serial transmission.
- Serial transmission suffers from little interference at high frequencies, so the serial frequency can be much higher than with parallel transmission. This results in higher net data transfer rates.
What is the bit rate?
What unit is it measured in?
The number of bits that are transferred between devices in one second.
It’s measured in bits per second. (Typically megabits or gigabits per second).
What is the baud rate?
What unit is it measured in?
Number of signal changes in a communications channel per second.
It’s measured in bauds.
What is the relationship between bit rate and baud rate?
bit rate = baud rate × number of bits per signal
What is bandwidth?
What unit is it measured in?
A measure of the maximum capacity of a given communication channel.
(Bandwidth and bit rate are directly proportional).
It is measured in hertz.
What is latency?
Time delay between the moment an action is initiated and the moment its effect begins.
What is synchronous transmission?
Data is transferred at regular intervals which are synchronised by a clock pulse signal.
What is asynchronous transmission?
Each byte is sent separately and the receiver and transmitter do not need to be synchronised, as the bytes are sent as soon as they are ready. To control the communication start and stop bits are used.
What is the relationship between bit rate and bandwidth?
Bit rate is directly proportional to bandwidth.
Explain how it is possible for the number of bits transmitted per second to be higher than the baud rate.
More than one bit is encoded in each signal change
What do start and stop bits do in asynchronous transmission?
The start bit is used to synchronise a clock in the receiving device. This means both devices are in step.
Once that has been received, timed periods will be used to receive the remaining bits in the transmission.
A stop bit indicates the end of the data.
The stop bit allows the receiver to identify when the next start bit arrives.
What is an advantage of using synchronous transmission over asynchronous transmission?
Faster transmission because fewer bits have to be transmitted.
What are the differences between a client and a server?
- Client sends requests, server sends responses
- Server can decide which data is sent, whereas client cannot
- Servers are usually always on, whereas clients do not need to be
- Clients are user facing, whereas servers are not
Explain why it is common practice for servers to be always running and for clients to be sometimes running?
- Clients should be able to connect at any time to the server
- The client only needs to be running while the user is accessing the service
- If the server is shut down, no one will be able to access the service
An advantage of peer-to-peer networks over client-server models is that they are cheaper for the founder to run. Explain why this is the case.
Servers are more expensive to run because they are more powerful machines, they need more storage space and they need to be always powered on. In p2p, no one is responsible for a server. As more hosts connect to a p2p network, the resource supply increases, whereas when more hosts connect to a single server, the more powerful and expensive the server machines need to be.
What are the advantages and disadvantages of thick client computers?
Advantages:
• Internet connection not needed to do useful stuff
• Can be used for storage of many files and large files
• More flexible in what can be done (whereas thin are limited to what cloud-based services exist and how they work)
Disadvantages:
• More expensive to buy and maintain
• Sometimes harder to use
• Sometimes less secure because the user is responsible for management of files and programs
Explain why a client-server network is likely to be more appropriate than a peer-to-peer network in a situation where a system (for the administration of student courses to be used in an office in a college) must allow users at ten workstations to access and update a central database
- System will be storing confidential data that must be kept securely
- Administration will be easier
- Centralised backup
- Harder for users to change security settings
- Running database from a server will avoid concurrency issues
- Running database from server will ensure that it is always available
- Server may allow more simultaneous connections than a workstation
Explain the differences between client-server and peer-to-peer networking
With client-server networking: • Resources are stored on the server • Clients access resources from server • Centralised security management • Configuration requires greater expertise
With peer-to-peer networking:
• Resources stored on each individual computer
• Any computer can access resources from any other
• Each computer has equal status
• Management of security could be more difficult
• There is no dependence on a server
Describe the different parts of the URL http://www.aqa.org.uk/qual/gce/computing_new.php
- http://
- www.aqa.org.uk
- /qual/gce/computing_new.php
- http:// → the protocol used
- www.aqa.org.uk → address of Aqa’s World Wide Web server
- /qual/gce/computing_new.php → the path of the resource
