(4.9) Fundamentals of communication and networking Flashcards
Definition of serial transmission
The transmission of data through a single channel a single bit at a time
Definition of parallel transmission
The transmission of data through multiple channels allowing for several bits to be transmitted at a time
Advantages of serial over parallel transmission
- Serial transmission requires less wires and hardware, therefore less cost
- Serial transmission doesn’t require the data to be kept synchronised across wires
- Serial transmission doesn’t skew so better for transmission over long distances
- No crosstalk between wires, less chance of errors
Definition of synchronous data transmission
Data transmitted with a shared clock signal, ensuring synchronized timing.
Definition of asynchronous data transmission
Data transmitted intermittently between devices without the use of an external clock signal
The purpose of start and stop bits in asynchronous data transmission
Start and stop bits in asynchronous transmission mark the beginning and end of data packets, ensuring synchronization
Compare asynchronous and synchronous data transmission
Synchronous data transmission uses a clock signal for synchronization, while asynchronous relies on start and stop bits for timing
What is baud rate?
The number of times the signal in a communications channel changes state
What is bit rate?
The number of bits transmitted per unit time
What is bandwidth?
The range of frequencies at which data can be transmitted through a channel, measured in Hertz
What is latency?
The time delay between the transmitter sending the data and the recipient receiving the data
What are protocols?
A common set of rules followed during data transmission over a network to minimise inconsistencies
What is the difference between baud rate and bit rate?
Bit rate measures bits transmitted per second, while baud rate measures signal changes or symbols per second
Bit rate can be higher than baud rate if more than one bit is encoded i each signal change
What is the relationship between bit rate and bandwidth?
The greater the bandwidth, the higher the bit rate
(they are directly proportional)
What is the phsical star topology?
- Each client has its own direct connection to a central hub
- The hub receives packets for all of the clients and delivers them to the correct recipient
- A server can be added to the network in the same way that clients are connected to the central hub
Advantages and disadvantages of star topology
Advantages:
* Easy to add and remove clients
* Collisions don’t happen because each cable only has one device communicating over it
* Failure of one cable doesn’t affect the rest of the network
Disadvantages:
* Central hub/switch is a single point of failure
* Expensive to install because of the amount of cable required
What is the physical bus topology?
- Connects clients to a single (cable called a backbone)
- Terminators are present at either end of the backbone
- No need for a central hub
- A server can be connected to the backbone just like a client
Advantages and disadvantages of bus topology
Advantages:
* cheap to install
* Only requires backbone, no additional hardware
Disadvantages:
* Poor security, every client can see packets even if not intended for them
* central point of failure, the entire network becomes unstable if backbone fails
What is logical network topology?
The flow of data packets within a network
* A logical bus network delivers packets to all clients on the network
* A logical star network delivers packets only to their recipient
Mixing topologies
If a network is set up as a physical star, it can still behave as a logical bus
Even if physical connections follow that of the physical star topology, running a bus protocol on the hub allows it to distribute packets to all of the connected clients so as to act like a bus network
What is peer-peer networking? (& Advantages and disadvantages)
- Each computer has an equal status
- Do not use a shared server
- Services are provided by the clients themsleves
Advantages:
* More cost effective as no server required
* Easier to set up and maintain
Disadvantages:
* Clients have to be running to provide services
* Only works for smaller scale networks
What is client-sever networking? (& Advantages and disadvantages)
- One or more central servers provide services to clients on networks
- Has a central point of management and security
- Clients request services from servers, which respond to clients with requested service
Advantages:
* Can improve network security
* Can connect clients over larger distances
Disadvantages:
* Harder to set up and maintain, may require network manager
* Larger costs as servers can be expensive
Situations where peer-peer and client-server networks would be used
Client-server networks:
* organisations with many computers
* situations where many computers need access to the same information
* Many schools use this type of model
Peer-peer networks:
* smaller organisations that have fewer computers
* where fewer computers need access to the same data
The purpose of WiFi
- A wireless local area network (LAN) 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 are wireless networks secured?
- Encryption of data using WPA/WPA2 (wifi protected access)
- SSID (service set identifier) broadcast disabled
- MAC (media access control) address allow list
Explain the wireless protocol Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) & the problem with it
- Device listens to its communication channel to check whether it is idle
- If so, data is transmitted
- If not, device waits a random period of time before checking the channel again
Problem: CSMA/CA cannot overcome hidden nodes
–> when the device checking for an idle channel cannot ‘see’ some parts of the network, leading to collisions
Explain the wireless protocol Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) with Request to Send/Clear to Send (RTS/CTS)
To avoid the problem of hidden nodes, the protocol RTS/CTS is used
* Device listens to its communication channel to check whether it is idle
* If so, a ‘request to send’ message is sent to the server
* If the server is idle, it responds with a ‘clear to send’ message, and the device begins transmission
* if no ‘clear to send’ message is recieved, the server is communicating with a hidden node and transmitting device must wait before starting CSMA process again
What are Service Set Identifiers (SSID)?
An SSID is a name that identifies a wireless network
