TCP/IP protocol family architecture--network communication

Computers and network devices need to follow the same rules to communicate with each other. For example, how to find the communication target, which language to use for communication, how to end the communication, etc. The communication between different hardware and operating systems needs to follow the same rules, which are also called protocols. This article mainly discusses the TCP/IP protocol family related to the Internet from the following three points.

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• What is TCP/IP protocol suite?
• TCP/IP protocol four-layer model and the benefits of layering
• The relationship between TCP/IP protocol model and ISO/OSI model 7-layer model

1. What is the TCP/IP protocol suite?

The TCP/IP family is a general term for a collection of various Internet-related protocols, as shown in the following figure

2. TCP/IP protocol four-layer model

An important point about TCP/IP is that it is layered. Each layer performs different functions and is implemented through several protocols. The upper layer protocol uses the services provided by the lower layer protocol. It is usually divided into the following four layers

• Application Layer
• Transport Layer
• Network Layer
• Network Interface Layer

• Application layer: determines the communication activities when providing application services to users, such as HTTP protocol, FTP protocol for file transfer, SMTP for email sending, DNS protocol for domain name resolution, etc.
• Transport layer: provides data transmission between two computers in a network connection (TCP transmission control protocol and UDP user datagram protocol).
• Network layer: handles the routing and forwarding of data packets flowing on the network. It specifies the transmission path of the data packets to reach the target computer and sends the data packets to the other party. The IP protocol is a network layer protocol (IP data packet).
• Network interface layer: handles the hardware part connected to the network, such as controlling the operating system, network card, optical fiber, etc., and is responsible for receiving IP datagrams and sending these datagrams to the specified network.

The advantage of layering is that it makes the design more flexible. For example, if the Internet is coordinated by only one protocol, if some parts need to be modified, it will affect the whole. After layering, you only need to replace the layer that needs to be modified. By planning the interface between each layer, the layers are decoupled, and then each layer can be freely designed and modified.

3. The relationship between the TCP/IP protocol model and the ISO/OSI model 7-layer model

• The ISO/OSI model, or the Open Systems Interconnection Reference Model, is a standard framework proposed by the International Organization for Standardization (ISO) that attempts to interconnect various computers into a network worldwide, referred to as OSI.
• The TCP/IP protocol model includes a series of network protocols that form the basis of the Internet. The TCP/IP protocol suite is a combination of multiple protocols at different levels and is usually considered to be a four-layer (or five-layer) system, corresponding to the OSI seven-layer model.

Relationship: ISO/OSI model is an open communication system interconnection reference model (7-layer model), and network communication interconnection is implemented with reference to this model. The TCP/IP protocol model divides the protocols in the TCP/IP protocol family into each layer of the four-layer model. According to the corresponding relationship between the TCP/IP model and the ISO/OSI model in the following figure, the place (layer) where each protocol in the protocol family plays the role of rules in the open communication system interconnection reference model is mapped.

Summarize

The TCP/IP family is composed of multiple protocols related to the Internet. One of the key points of TCP/IP is that it is divided into a four-layer model. Each layer performs different functions and corresponds to several protocols. The upper layer protocol uses the services provided by the lower layer protocol. The benefit of layering is that it makes design modifications easier. The ISO/OSI model is an open communication system interconnection reference model. By corresponding to the TCP/IP model, we can know the position of each protocol in the TCP/IP protocol family in the communication system interconnection reference model.