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preface
Network models are basic but important network basics. The OSI seven-layer model and TCP/IP four-layer model and five-layer protocol model are often talked about now.
OSI seven layer model
It’s called the OSI(Open System Interconnection) model or the seven-tier model. It is the international Standardization (ISO) set a standard system for the interconnection of computers or communication systems. The protocol divides the computer network architecture into seven layers.
Each layer implements its own functions and protocols, and completes interface communication with adjacent layers. The services provided by each layer are the result of collaboration between that layer and the layers below.
| The hierarchy | The OSI model | explain |
|---|---|---|
| 7 | Application Layer | An interface between a network service and an end user |
| 6 | Presentation Layer | Data formatting, conversion, encryption |
| 5 | Session Layer | Establish, manage, and terminate sessions between different machines |
| 4 | Transport Layer | Defines the protocol port numbers for transmitting data, as well as flow control and error-checking |
| 3 | Network Layer | Logical address addressing to realize the path selection between different networks |
| 2 | Data Link Layer | Provides media access and link management |
| 1 | Physical Layer | Establish, maintain, and disconnect physical connections that transfer binary data |
TCP/IP four layer model and five layer protocol model
In fact ICP/IP is a four-tier model, but later for the convenience of understanding the network principle, the seven-tier model and the four-tier model are integrated, and a five-tier model is produced. The five-layer model only divides the network interface layer into two layers: data link layer and physical layer
| The hierarchy | ICP/IP model | explain |
|---|---|---|
| 4 | The application layer | Provide users with all kinds of services they need |
| 3 | The transport layer | It provides end-to-end communication function for application layer entities, ensuring sequential transmission of data packets and data integrity |
| 2 | The network layer | It mainly solves host-to-host communication problems |
| 1 | Network interface layer | Responsible for monitoring the exchange of data between host and network |
An analogy of the three models
| TCP/IP four-tier model | TCP/IP four-tier model | The OSI model |
|---|---|---|
| The application layer | The application layer | The application layer |
| The presentation layer | ||
| The session layer | ||
| The transport layer | The transport layer | The transport layer |
| The network layer | The network layer | The network layer |
| Network interface layer | Data link layer | Data link layer |
| The physical layer | The physical layer |
The same
- Both the OSI and TCP/IP models adopt the concept of hierarchy
- Both can provide both connection-oriented and connectionless communication service mechanisms.
The difference between
- The network interface layer of the TCP/IP reference model is not really defined, just a conceptual description. The OSI reference model not only has two layers, but the functionality of each layer is detailed.
- OSI model is designed before protocol development and has universality. TCP/IP has a protocol set and then builds a model. It is not applicable to non-TCP /IP networks