Classification of protocols
The protocols are normally implemented in software by using one of the common programming languages.
Classification of Protocols:
- Protocols can be classified on the basis that can be used for noiseless (error-free) channels and those that can be used for noisy (error-creating) channels.
- The protocols in the first category cannot be used in real life, but they serve as a basis for understanding the protocols of noisy channels.
- Figure 2.4 shows the classifications
- All the protocols unidirectional in the sense that the data frames travel from one node, called the sender, to another node, called the receiver.
- Although special frames, called acknowledgment (ACK) and negative acknowledgment (NAK) can flow in the opposite direction for flow and error control purposes, data flow in only one direction.
- In a real-life network, the data link protocols are implemented as bidirectional; data flow in both directions.
- In these protocols the flow and error control information such as ACKs and NAKs is included in the data frames in a technique called piggybacking.