Switching Modes in Computer Network

Layer 2 switches are used for data transmission on the data link layer, as well as error checking on sent and received frames. Layer 2 switches forward packets based on the MAC address. Switching modes refer to the various modes utilised to forward packets.

Different portions of a frame are recognized in switching mode. The frame is made up of many components, including a preamble, the destination MAC address, the source MAC address, the user’s data, and the Frame Check Sequence (FCS).

Types of Switching Modes:

1. Store-and-forward switching mode:

The store-and-forward method involves intermediate nodes storing the received frame temporarily and then checking for faults in that frame before dispatching it to the next node.

The layer 2 switch waits until the full frame has been received before proceeding. When the full frame is received, the switch stores it in the switch buffer memory. This is referred to as storing the frame.

After the frame has been saved, it is verified for errors. If an error is detected, the message is discarded; otherwise, it is sent to the next node. This is referred to as advancing the frame.

The CRC (Cyclic Redundancy Check) technique is used to check for mistakes in the received frame by using a number of bits.

The store-and-forward approach provides a high level of security since the corrupted frames do not affect the target network.

Store-and-forward switches are extremely reliable since they do not forward colliding frames.

2. Cut-through switching mode:

Cut-through switching is a technique in which the switch transmits packets after identifying the target address rather than waiting for the complete frame to be received.

Whenever a frame is received, the switch immediately checks the first 6 bytes after the preamble, and then checks the destination in the switching table to identify the outgoing interface port and then passes the frame to the destination.

Because the switch does not wait for the whole frame to be received before delivering packets to the destination, it has a low latency rate.

It lacks an error-checking method. As a result, the mistakes might be delivered to the receiver with or without errors.

Cut-through switching has a short wait time since it forwards packets as soon as it recognises the target MAC address.

Collision detection is not used in this approach, thus frames that have collided will be transmitted as well.

3. Fragment-free switching mode:

Fragment-free switching is a more sophisticated Cut-through Switching method.

To ensure error-free transmission, fragment-free switching reads at least 64 bytes of a frame before forwarding to the next node.
It combines the speed of Cut-through Switching with the functionality of error checking.

This method examines the 64 bytes of the ethernet frame that include addressing information.

When a collision is discovered inside the first 64 bytes of a frame, the frames that are collided are not sent any further.

Difference between Store-and-forward switching and Cut-through switching:

Summary:

In this article, we looked at the concept of switching modes, and we also looked at the three main modes of switching, which are: Store-and-forward, cut-through, and fragment-free. We also looked at the differences between the store-and-forward method and cut-through methods.