24 Questions
What is the primary function of error correction in data transmission?
To detect and correct errors without contacting the sender
What is the key difference between half-duplex and full-duplex transmission?
Half-duplex allows nodes to transmit and receive at different times, while full-duplex allows nodes to transmit and receive simultaneously
What is the main reason for signal attenuation in long-distance transmission?
Weak signal strength due to long distance
Which of the following is NOT a type of signal interference?
Amplification
What is the primary function of the link layer in data transmission?
To provide error correction and detection mechanisms
What is the purpose of firmware in a Network Interface Card (NIC)?
To act as an intermediary between software and hardware
Which type of multiplexing is used to implement half-duplex transmission?
Time Division Multiplexing (TDM)
What is the primary function of a Network Interface Card (NIC)?
To implement both data link and physical layer services
What is the primary reason for implementing flow control in network communication?
To ensure the receiver's buffer does not overflow
What is the main difference between error detection and error correction?
Error detection signals the sender for retransmission, while error correction corrects the error without retransmission
What is the effect of signal attenuation on a transmitted signal?
It decreases the amplitude of the signal
What is the main cause of noise in network communication?
All of the above
What is the purpose of error detection in network communication?
To detect errors in the received data and signal the sender for retransmission
What is the main difference between half-duplex and full-duplex transmission?
Half-duplex transmission is unidirectional, while full-duplex transmission is bidirectional
What is the effect of noise on a transmitted signal?
It weakens the signal
What is the primary purpose of flow control in network communication?
To ensure the receiver's buffer does not overflow
What is the primary concern that necessitates the use of MAC protocol in a shared medium?
To prevent collisions and ensure correct data interpretation
What is the primary purpose of reliable delivery in the link layer?
To guarantee datagram transmission across the link without error
Why is reliable delivery service not always provided in the data link layer?
Because it is not necessary for all types of links
What is the advantage of using MAC protocol in a shared medium?
It coordinates frame transmission and prevents collisions
Why do wireless links require reliable delivery service in the data link layer?
Because they have high bit error rates
What is the purpose of adding MAC addresses to the frame header?
To identify the source and destination of the frame
What type of links do not require reliable delivery service in the data link layer?
Fiber optic links
Why is it necessary to have a mechanism to coordinate frame transmission in a shared medium?
To prevent collisions and ensure correct data interpretation
Study Notes
Link Layer Services
Flow Control
- Flow control is necessary to adjust the pacing between adjacent sending and receiving nodes to avoid full buffer at the receiver.
- If the sender transmits frames at a higher speed than the receiver can handle, it will overwhelm the receiver and incoming data will be dropped.
Error Detection and Correction
- Error detection is the process of detecting errors caused by signal attenuation, noise, and other signal distortions.
- Error correction is the process of identifying and correcting bit errors without resorting to retransmission.
- Attenuation is the reduction in power of the signal as it is transmitted over long distances, requiring repeaters.
- Noise refers to any external, unwanted information that interferes with a transmission signal.
Half and Full Duplex
- Half-duplex allows nodes to transmit, but not at the same time, using time division multiplexing.
- Full-duplex allows both nodes to transmit simultaneously, using frequency division multiplexing.
Link Layer Implementation
- The Link Layer is implemented in the Network Interface Card (NIC) or on a chip.
- NICs have their own CPU and RAM.
- Ethernet cards are responsible for Ethernet communication, while 802.11 cards are responsible for wireless communication.
- The NIC implements both the Data Link and Physical layers.
MAC Protocol
- In a shared medium/broadcast link, the MAC protocol coordinates frame transmission to avoid collisions.
- MAC addresses are added to the frame header to identify source and destination frames.
- The MAC protocol controls how the shared medium is accessed and decides which frame is transmitted on the link and when.
Link Layer Services - Reliable Delivery
- Reliable delivery is used to guarantee the movement of datagrams across a link without error.
- It is seldom used on low-bit-error links, such as fiber and some twisted pair cables.
- Wireless links, with high error rates, require reliable delivery in the data link layer.
Learn about flow control in link layer services, including scenarios where the sender transmits frames at higher speeds than the receiver can handle, and how to avoid overwhelming the receiver.
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