Flow Control in Data Link Layer
Flow control is design issue at Data Link Layer. It is a technique that generally observes the A design issue at the data link layer is flow control. It is a method that typically monitors the correct data flow from sender to receiver. It is very important because it allows the sender to send data or information at a very quick rate, which allows the receiver to receive it and process it. This is only possible if the receiver has a significantly higher traffic load than the sender or if the receiver has lower processing power. The basic idea behind flow control is to allow two stations that are operating and processing at different rates to simply communicate with one another. Data Link Layer flow control merely limits and coordinates the number of frames or amount of data that can be sent by the sender before it waits for a response from the recipient. The term “flow control” refers to a set of procedures that inform the sender of the maximum amount of data or frames that can be sent without overwhelming the receiver. Additionally, the receiving device has a meagre amount of speed and memory for data storage. This is why the receiving device should be able to inform the sender to temporarily halt data transmission or transfer before it reaches a limit. Additionally, it requires a buffer, a sizable memory block used only for storing data or frames until they can be processed.
- Feedback based Flow Control In these protocols, the sender only sends frames after receiving user acknowledgements. The data link layer uses this.
- Rate based Flow Control These protocols incorporate controls to limit the rate of transmission of information without requesting a response from the recipient. Both the network layer and the transport layer employ this.
Two methods have been developed to control the flow of data:
- Stop-and-wait
- Sliding window
Stop-and-wait
- Every frame that is sent using the Stop-and-wait method is followed by a wait for an acknowledgement.
- The following frame is only sent after acknowledgment has been received.
Advantages –
- Every frame is checked and acknowledged properly using this method, which is also very simple and easy.
- This approach is also very precise.
Disadvantages –
- This approach takes a while.
- One packet or frame can only be sent at a time in this.
- It causes the transmission process to move very slowly and is very inefficient.
Sliding Window
By allowing multiple frames to be transmitted before receiving an acknowledgment, this protocol enhances the effectiveness of the stop and wait protocol.
The following list explains how this protocol operates:
- Both the sender and the receiver has finite sized buffers called windows. The sender and the receiver agrees upon the number of frames to be sent based upon the buffer size.
- Sender sends numerous messagesframes in a sequence, without requesting confirmation. once its The sending window is full and waiting for a response. Upon receiptacknowledgment, it moves the window forward and sends the following frames.based on the quantity of acknowledgements obtained.
Advantages –
- This method increases efficiency.
- Compared to stop-and-wait flow control, it works much better.
- Sending multiple frames in succession is possible.
Disadvantages –
- The complexity at the sender and receiver caused by the transmission of multiple frames is the main problem.
- Data frames or packets may be received by the receiver out of order.