Data Link Layer Overview

These flashcards cover key concepts related to the functions and mechanisms of the Data Link Layer in the OSI model.

What is the primary responsibility of the Data Link Layer (Layer 2) of the OSI model?

The Data Link Layer is responsible for the logical organization and management of data communication over a single link.

What are the three primary functions of the Data Link Layer?

Link Management, Flow Control, and Error Control.

What is Link Management in the context of the Data Link Layer?

It involves setting up, monitoring, controlling, and tearing down a connection.

What does Flow Control aim to achieve?

Flow Control prevents a sender from overwhelming a receiver with data, matching the transmission rate to the receiver's capacity.

Describe Stop and Wait Flow Control method.

The transmitter sends one frame and waits for an acknowledgment (ACK) before sending the next frame.

What is a disadvantage of Stop and Wait Flow Control?

It is generally inefficient, especially for small frames over long distances due to waiting for acknowledgments.

How does Sliding Window Flow Control improve efficiency?

It allows the transmitter to send multiple frames before needing to wait for an acknowledgment.

What is the significance of window size in Sliding Window Flow Control?

The window size is determined by the number of bits reserved for sequence numbers, affecting how many frames can be sent before waiting for an ACK.

What is Automatic Repeat Request (ARQ)?

ARQ refers to error control methods that handle errors in transmitted frames.

What happens in Stop and Wait ARQ when an error is detected?

The receiver discards the frame and sends a Negative Acknowledgment (NAK), prompting the transmitter to resend the frame.

Explain the Back-N ARQ method.

If an error is detected, the receiver requests the retransmission of the erroneous frame and all subsequent frames.

What is the efficiency of Selective Reject ARQ?

It retransmits only the errored frame, allowing the receiver to buffer and reorder correctly received frames, making it more efficient.

What are common error detection methods used in the Data Link Layer?

Parity Bits and Cyclic Redundancy Check (CRC).

What is the function of the Frame Check Sequence (FCS) in HDLC?

FCS is a 16-bit CRC value used for error detection.

What is bit stuffing in HDLC frames?

Bit stuffing is the process of inserting a zero after every five consecutive ones to prevent synchronization errors.

How does the Address Field function in HDLC?

It identifies the specific station in multi-point connections, allowing for unique addresses or broadcast messages.

Why are modern protocols based on HDLC significant?

They demonstrate foundational importance in data communications, incorporating the structure and operational principles of HDLC.