Unit 6 - Communications Flashcards
(21 cards)
What are the two main issues with parallel data transmission?
Parallel data transmission suffers from skew, where the data in individual wires is sent a varying speeds, and crosstalk, where the adjacent wires interfere electromagnetically.
Why is serial data transmission faster than parallel at very high speeds?
The problem of crosstalk within parallel transmission is amplified as the frequency of transmission increases.
What three additional bits have to be transmitted during asynchronous transmission? (one is related to the chance of error)
- The start & stop bits are added to form breaks in transmission between bits.
- A parity bit is included for error checking.
What’s the main difference in the performance of asynchronous transmission vs synchronous?
Asynchronous transmission is slower due to having to transfer an extra 3 bits per 8. It is cheaper and is therefore suitable for low-speed connections.
What is the general definition for a protocol?
A protocol is a set of rules governing some sort of communication between two devices.
What is the bit rate of a transmission?
Bit rate is the number of bits being transferred per second.
How many bits are transmitted per signal change when using baseband?
One bit is transmitted per signal change.
What is the baud rate of a transmission?
The baud rate is the frequency at which the signal in a transmission changes state. Data is sent at each of these signal changes.
What is the difference between baseband and broadband?
Broadband transfers more than one bit per state change, so bit rate > baud rate.
What is the bandwidth of a network?
The bandwidth of a network is the maximum capacity of a communications channel.
Advantages of a bus network:
- Inexpensive to set up
- Devices can easily be added
- Good for small networks
Disadvantages of a bus network:
- Entirely reliant on main cable
- Limited cable length
- Performance degrades with increased use
- Poor security
What protocol is used on a wired network to prevent multiple transmissions happening at once?
CSMA/CD is used (Carrier Sense Multiple Access/Collision Detection).
What are the two pieces of hardware that can be used for the central node of a wired star network and how are they different.
The central node of a star network can be a hub, which broadcasts received messages to all other devices on the LAN, or a switch, which forwards messages to their intended destination.
What address is attributed to the Network Interface Card of all devices?
They are attributed a Media Access Control (MAC) address.
What does a network need to connect to a wireless network? (4/5 things)
- An internet service provider
- A modem and wireless router
- A device with a Network Interfacing Card
- A wireless access point
What is required for a device to be able to connect to a wireless network?
All wireless networks require a Network Interfacing Card for a device to connect.
What is an SSID?
An SSID is a Service Set Identifier and is used by all devices connected to a network. It provides a name to identify the network by.
What protocol is used to avoid multiple devices communicating at once, leading to interference?
CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) is used. The device checks the channel and only communicates if it is empty. RTS/CTS (Request To Send/Clear To Send) is also used to avoid the problem of “hidden nodes”.
What is a the “hidden node” problem?
The hidden node problem occurs when two devices are connected to a WAP, but they are unable to detect each other due to being out of each others range.
What is shared between two communicating devices using public key cryptography? (cannot explain full process in flashcard format)
The two devices will send each other their public keys.
