MAC Sub Layer Study Notes

Study Notes

MAC Sub Layer Study Notes

MAC Addressing

A MAC (Media Access Control) address is a unique identifier for network interfaces.
Consists of 48 bits, typically expressed as 12 hexadecimal digits.
Each network interface card (NIC) has a globally unique MAC address.
MAC addresses are divided into:
- Universal (or Multicast) addresses: used to identify devices on a network.
- Local (or Unicast) addresses: identify specific devices.
Address types include:
- Unicast: one-to-one communication.
- Broadcast: one-to-all communication within a local network.
- Multicast: one-to-group communication.

Collision Detection

Collision occurs when multiple devices transmit simultaneously on a shared medium.
Utilizes CSMA/CD (Carrier Sense Multiple Access with Collision Detection) in wired networks.
Steps in collision detection:
1. Devices listen (carrier sense) before transmitting.
2. If the medium is clear, they send data.
3. If a collision is detected, devices stop transmitting and send a jam signal.
4. Devices wait a random backoff time before trying to transmit again.

Frame Structure

Frames are the data packets used at the MAC layer, containing:
- Preamble: Syncs and indicates the start of a frame.
- Destination MAC Address: Identifies the receiving device.
- Source MAC Address: Identifies the sending device.
- Type/Length Field: Indicates the type of data or the length of the data field.
- Data Payload: Contains the actual data being transmitted.
- Frame Check Sequence (FCS): Error-checking mechanism to ensure data integrity.

IEEE 802 Standards

The IEEE 802 family includes various networking standards, such as:
- IEEE 802.3: Defines Ethernet (wired) networks.
- IEEE 802.11: Defines wireless LANs (Wi-Fi).
- IEEE 802.15: Addresses wireless PANs (Bluetooth).
- IEEE 802.16: Focuses on broadband wireless access (WiMAX).
Each standard specifies MAC layer functionalities and mechanisms.

Flow Control Mechanisms

Ensure efficient data transmission without overwhelming network devices.
Common flow control techniques include:
- Stop-and-Wait: Sender transmits a frame and waits for an acknowledgment before sending the next.
- Sliding Window Protocol: Allows multiple frames to be sent before needing an acknowledgment, improving throughput.
- Acknowledgments: Receiving devices send confirmations upon receiving frames, prompting further transmission.
Flow control avoids data loss and optimizes network performance.

MAC Addressing

MAC addresses uniquely identify network interfaces.
48-bit addresses (12 hexadecimal digits).
Globally unique for each NIC.
Address types: Unicast (one-to-one), Broadcast (one-to-all), Multicast (one-to-group).

Collision Detection (Wired Networks)

CSMA/CD handles simultaneous transmissions.
Process: Carrier sense, transmit if clear, collision detection, jam signal, random backoff.

Frame Structure

Preamble: Frame synchronization.
Destination MAC Address: Receiving device identification.
Source MAC Address: Sending device identification.
Type/Length Field: Data type or length.
Data Payload: Transmitted data.
Frame Check Sequence (FCS): Error detection.

IEEE 802 Standards

Defines various networking technologies.
Examples: 802.3 (Ethernet), 802.11 (Wi-Fi), 802.15 (Bluetooth), 802.16 (WiMAX).
Each standard specifies MAC layer functions.

Flow Control Mechanisms

Prevent network overload.
Methods: Stop-and-Wait (single frame transmission), Sliding Window (multiple frames), Acknowledgements (confirmations from receiver).
Improves transmission efficiency and prevents data loss.

Description

This quiz covers the essential aspects of MAC addressing, including the significance of unique MAC addresses, types of addresses, and the mechanisms used for collision detection in network communications. It provides an overview of how devices communicate over a network and the protocols like CSMA/CD that ensure efficient data transmission.