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Questions
Jane tells Tony "Parallel transmission is always faster than serial transmission because you can transfer more bits at once."
Explain the factors jane may have forgotten that could make her statement untrue. (4 marks)
Skew (1) The further the data travels, the more likely it is that bits may not arrive at the same time (1)
Crosstalk (1) Interference between lines can cause data to need to be resent (1)
With reference to the image below explain why the bit rate and the baud rate are different (2 marks)
The baud rate is the number of times the signal changes per second (1)
The bit rate is the baud rate multiplied by the number of bits encoded in each signal therefore in this case the bit rate will be twice the baud rate (1)
Explain how start and stop bits are used in asynchronous transmission. (3 marks)
In asynchronous transmission data is sent only as it is needed to be in bytes
The start bit notifies the receiver data is about to be sent and synchronises the clock
The stop bit allows the receiver time to identify
the next start bit
Ramesh runs a law firm. He is setting up a network for an office of 25 lawyers. Explain 3 benefits to Ramesh of using a star topology instead of a bus network (3 marks)
Any 3 from:
If one cable fails only one workstation is affected
Easier to identify faults on the network
Consistent performance when in high use
No problems with data collisions
The system is more secure as
messages are only sent to the machine that needs them
Easy to add additional terminals if necessary
Sometimes when there is a satellite link up on TV, the reporter asks a question but the person at the other end of the link doesn’t hear the question for several seconds. What is this problem called and why does it happen. (2 marks)
The problem is called latency (1) It is the result of the delay between when the first bit of data is sent and when it is received (1)
Explain the difference between the physical and logical topology of a network. (2 marks)
The physical topology is the actual way the network is physically laid out (1) The logical topology is the way data moves in the network (1)
Explain why it is more difficult to deal with illegal file sharing in a peer-to-peer network than in a client server network (3 marks)
The files are stored on multiple machines not a single server
This makes it harder to remove the files
And harder to identify who uploaded the original version of the file
Peter and Sally are both connected to the same wireless access point, but they are not in the same room. Neither Peter nor Sally, nor their devices, knows the other is connected to the same wireless access point. Explain the problem that could occur if they both try to transmit data at the same time and how this can be overcome. (4 marks)
Any 4 of:
This is the hidden nodes problem
Normally any node would check first to see if other nodes are transmitting before trying to transmit itself
In this case it would not see that the other device was trying to
transmit and so a collision could occur
To overcome this when it wants to send a request to send message is sent
Only when a clear to send message is received because other devices are not trying to transmit would the data
be sent.
Raoule would like to set up a wireless network in his home so he and his family can connect to the internet with their various personal devices. What hardware will be necessary for him to set up this network? (2 marks)
All devices that will connect need a wireless network adapter (1) He will also need a wireless access point they can connect to (1)
Raoule has heard that having a wireless network can leave you vulnerable to hackers. Explain two steps he can take to make his wireless network more secure (4 marks)
He can disable his SSID (1) So only those that know the name of his network can log in (1)
He can use a MAC address whitelist (1) To restrict which physical devices can connect to his network (1)
Explain what a WebSocket protocol is and when it may be used (2 marks)
A protocol that allows a persistent, bidirectional communication channel (1) essential for situations where both client and server need to communicate at the same time e.g. gaming (1)
Explain the advantages JSON has over XML for transferring data (3 marks)
Any 3 from:
Easier for humans to read
More compact so transfers quicker
Easier to create because it can use arrays
Easier for computers to parse and so quicker
What are the 4 fundamental operations of a database performed by a web CRUD application? (4 marks)
Create (1) Retrieve (1) Update (1) Delete (1)
Explain what a restful API is and the benefit of having a restful API. (2 marks)
One that uses HTTP request methods to interact with an online database through a web server (1)
It allows the client or server to be updated and developed independently without loss of function (1)
Describe the result of the HTTP request DELETE http://solarsystem.com/Planets/Jupiter (2 marks)
It will delete the record for the planet Jupiter
from the Planets table on the database connected to the website www.solarsystem.com
XYZ Travel are a travel company with 15 staff who each book flights and hotels for customers from their terminals. XYZ have decided to install a client server network but are not sure whether they should use thick or thin clients. Advise them of the advantages and disadvantages of each. (8 marks)
Any 8 from:
Thin advantages
Easy to set up, maintain and add new terminals
Software and updates installed on the server and automatically distributed to clients
More secure as all data is centrally stored
Thin disadvantages
Reliant on server - no server and terminals don't work
Requires a powerful server that is normally expensive
More demand placed on the server and bandwidth
More battery used than if processing is
done locally
Thick advantages
Robust and reliable, less downtime
Can operate without a continuous connection to the server
Better for running more powerful applications
Thick disadvantages
More expensive
terminals as they have a higher spec
Installation must be done on each client separately increasing network management time
Integrity issues with distributed data