2. Data transmission Flashcards
What happens to data before it is transmitted?
Data is broken down into packets before it is transmitted
What are the components of a data packet?
- Packet Header
- Payload (Actual data)
- Trailer
What does the packet header contain?
- Packet number
- Destination IP address
- Sender’s address
Describe the process of packet switching.
- Data is broken into packets
- Packets are given sequence numbers
- Packets are sent through different routes
- Routers determine the fastest route
- Packets arrive out of order
- Packets are reordered upon arrival
What is the difference between serial and parallel transmission?
Serial transmission: Sends one bit at a time down a single wire
Parallel transmission: Sends multiple bits simultaneously over multiple wires
What are the features of serial transmission?
- Used for long distances
- Reliable (no risk of data skewing)
- Less expensive (fewer wires)
- Slower than parallel transmission
What are the features of parallel transmission?
- Faster than serial transmission
- Best for short distances
- Can suffer from data skewing
- More expensive (more wires required)
What are the 3 modes of data transmission?
- Simplex: One direction only
- Half-duplex: Two directions, but not simultaneously
- Full-duplex: Two directions simultaneously
How is data transmitted using USB?
- USB uses serial transmission
- The computer detects the device automatically
- The appropriate driver is loaded automatically
What are the benefits of using USB?
- Universal standard
- Easy to connect (fits only in 1 way)
- Supports various data rates
- Provides power (5 V)
What are the drawbacks of using USB?
- Older USB versions may not be supported
- Maximum cable length is 5m
- Slower than Ethernet
Why is error detection necessary in data transmission?
Errors may occur due to electrical interference, packet switching issues, or data skewing
How does a parity check work?
- A parity bit is added to the data to check for errors
- Odd or even parity is used to detect changes in bits
What is a checksum, and how does it work?
- A checksum is a value calculated from the data using an algorithim
- The receiver recalculates the checksum to verify the data
What is an echo check?
- The receiving computer sends back the received data
- If it matches the original data, no error has occurred
What is a check digit and where is it used?
- A check digit is calculated and added to the end of a number to detect errors.
- Examples, ISBN, barcodes
Why is encryption needed in data transmission?
- Encryption turns data into an unreadable form to protect it from unauthorized process.
What is the difference between plaintext and ciphertext?
- Plaintext: Original readable data
- Ciphertext: Encrypted, unreadable data
How does an automatic repeat query (ARQ) work?
- Computers using ARQs will automatically send back a positive acknowledgment if a data packet is deemed correct or resent if an error is detected.
- If no acknowledgment is returned within a certain time period, a timeout is registered and the sending computer resends the packet.
- The process continues until the packet received is correct or until the ARQ’s limit is reached.
What is symmetric encryption?
Uses the same key for both encryption and decryption
What is asymmetric encryption?
- Uses two keys: A public key for encryption and a private key for decryption
Describe how the photographs would be transmitted using serial data transmission.
- Data is sent one bit at a time down a single wire
Give two benefits of transmitting the photographs using serial data transmission.
- Data won’t be skewed
- Less chance of error
State one benefit of the student using parallel data transmission instead of serial data transmission.
Data may be transmitted quicker
Explain how data is encrypted using symmetric encryption.
- Data is encrypted and decrypted using the same key
- Plain text is encrypted into cipher text
- Data is encrypted using an algorithm that uses a key
