Sub-layers of the Data Link Layer

Summary

This lecture explains the sublayers of the data link layer in the OSI model. It introduces two key sublayers: Logical Link Control (LLC) and Media Access Control (MAC). The LLC handles communication between the upper and lower layers, providing flow control by adding necessary control information to network data. The MAC sublayer is responsible for framing, physical addressing, error control, and placing frames onto the physical medium. The lecture also highlights the importance of both sublayers and ends with an activity to reinforce the concepts learned.

Takeaways

• 🖥️ The data link layer in the OSI model is divided into two sublayers: the Logical Link Control (LLC) and the Media Access Control (MAC).
• 🎯 The LLC or Data Link Control sublayer handles communication between the upper and lower layers, adding control information to help deliver packets to their destination.
• 🛡️ LLC is responsible for flow control, which ensures that data is transmitted efficiently between layers.
• 🔗 The MAC sublayer, which constitutes the lower sublayer, is typically implemented in hardware, such as the network interface card (NIC).
• ⚙️ The MAC sublayer manages two key responsibilities: data encapsulation and media access control.
• 📦 Data encapsulation involves assembling frames before transmission and disassembling them upon reception.
• 📡 The MAC sublayer adds headers and trailers to the packet from the network layer, creating the frames for transmission.
• 🆔 The MAC sublayer handles physical addressing or MAC addressing, framing, and error control.
• 🌐 The MAC sublayer is responsible for placing frames onto the physical medium at the sender's side and removing frames from the medium at the receiver's side.
• 📑 Flow control is managed by the LLC, while framing, MAC addressing, error control, and media access control are handled by the MAC sublayer.

Q & A

What are the two sublayers of the Data Link Layer in the OSI model?

The two sublayers of the Data Link Layer are the Logical Link Control (LLC) sublayer and the Media Access Control (MAC) sublayer.

What is the main role of the Logical Link Control (LLC) sublayer?

The main role of the LLC sublayer is to handle communication between the upper layers (like the Network Layer) and the lower layers (like the Physical Layer), as well as perform flow control by adding control information to help deliver packets to their destination.

What are the two primary responsibilities of the MAC sublayer?

The two primary responsibilities of the MAC sublayer are data encapsulation and media access control.

How does the MAC sublayer perform data encapsulation?

The MAC sublayer performs data encapsulation by assembling frames before transmission and disassembling frames upon reception. It also adds a header and a trailer to the Network Layer's Protocol Data Unit (PDU) to create a frame.

What are the three primary functions of the MAC sublayer?

The three primary functions of the MAC sublayer are framing, physical (MAC) addressing, and error control.

Which sublayer is responsible for flow control, and why is this important?

The Logical Link Control (LLC) sublayer is responsible for flow control, which is important because it regulates the flow of data between devices to prevent overwhelming a receiver with too much information at once.

What hardware component is associated with the MAC sublayer, and what role does it play?

The MAC sublayer is typically implemented in hardware within the network interface card (NIC), which directly interacts with the physical medium and is responsible for placing frames onto and removing them from the media.

What is media access control in the context of the MAC sublayer?

Media access control refers to the process where the MAC sublayer controls when and how frames are placed on the physical medium, ensuring that frames are sent or received without collisions and in accordance with the network protocols.

What type of addressing does the MAC sublayer handle, and why is it important?

The MAC sublayer handles physical addressing, also known as MAC addressing, which is important because it uniquely identifies devices on a local network to ensure that data is transmitted to the correct device.

How does the MAC sublayer contribute to error control?

The MAC sublayer contributes to error control by detecting and sometimes correcting errors that occur during the transmission of frames over the physical medium.