Error control
The Data Link layer or the DLL uses various techniques of error control to ensure that the data frames or packets are transmitted from the sender to the receiver with accuracy. Error control is the process of detecting and re-transmitting data frames that may be lost during transmission. Every time an attempt to remove errors during the transmission of data is made, some of the data frames are re-transmitted. This process is known as ARQ (Automatic Repeat Request).
Various techniques of error control:
- Stop-and-wait ARQ.
Stop-and-wait ARQ is one of the simplest flow and error control techniques. It is also known as alternating bit protocol. In this method, the receiver indicates its readiness to receive data. The sender sends information to the receiver, after that the sender stops and waits for acknowledgement or ACK. If ACK is received then it sends the next data packet, and if ACK is not received, then the sender tries again.
- Sliding Window ARQ.
It can be categorized into two types:
- Go-Back-N ARQ
- Selective-Repeat ARQ
Go Back ARQ
In this protocol, the sender keeps transmitting data packets even if it has not received any ACK. Go Back ARQ uses the Sliding Window protocol and continues to operate similarly to sliding window if no errors occur.
Selective Repeat ARQ
This technique is more efficient than Go Back ARQ as the lost packets are re-transmitted. But it is used less as it is a complex technique.
Error control