TCP/IP layer-4 model and OSI Layer-7 Model

TCP/IP layer-4 model and OSI Layer-7 Model
Table 1-1 is the table corresponding to the TCP/IP layer-4 model and the OSI Layer-7 model. We map the OSI Layer-7 network model with the Linux TCP/IP layer-4 concept model, and then classify various network protocols.
Table 1-1 TCP/IP layer-4 model and OSI Layer-7 Model

OSI Layer-7 Network Model	Linux TCP/IP layer-4 Conceptual Model	Corresponding network protocol
Application)	Application Layer	TFTP, FTP, NFS, WAIS
Presentation layer (presentation)		Telnet, rlogin, SNMP, Gopher
Session Layer)		SMTP, DNS
Transport)	Transport Layer	TCP, UDP
Network)	Internet Layer	IP, ICMP, ARP, RARP, AKP, uucp
Data Link)	Network Interface	FDDI, Ethernet, ARPANET, pdn, slip, PPP
Physical Layer (physical)		IEEE 802.1a, IEEE 802.2 to IEEE 802.11

1. Network Interface

The Network Interface puts the data link layer and the physical layer together and corresponds to the network interface of the TCP/IP conceptual model. The corresponding network protocols are Ethernet, FDDI, and any protocol that can transmit IP data packets.

2. Internet Layer

The network layer corresponds to the Internet layer of the Linux TCP/IP concept model. The Network Layer Protocol manages data transmission between discrete computers. For example, the IP protocol provides information packet transmission methods for users and remote computers, make sure that the information package reaches the target machine correctly. In this process, IP and other network layer protocols are used for data transmission. If some tools are not used to monitor system processes, users cannot see the IP addresses in the system. The network sniffer sniffers is a device that can see these processes (it can be software or hardware), it can read every packet sent through the network, that is, it can read any activity that occurs in the network layer protocol, because the network sniffer sniffers will pose a threat to security. Important network layer protocols include ARP, ICMP, and IP.

3. Transport Layer

The transport layer corresponds to the transport layer of the Linux TCP/IP conceptual model. The transport layer provides communication between applications. Its functions include formatting information flows and reliable transmission. To implement the latter, the transport layer protocol requires the receiving end to send back the confirmation message. If the group is lost, the receiver must resend the message. The transport layer includes TCP (Transmission Control Protocol) and UDP (User datagrams Protocol), which are the most important protocols in the transport layer. TCP is built on an IP address and defines the data transmission format and rules for programs on the network, it provides a mechanism for confirming the transmission of IP data packets, re-requesting lost data packets, and re-assembling received data packets according to their sending order. TCP is a connection-oriented protocol. Similar to a call, a clear connection must be established before data transmission starts. UDP is also built on an IP address, but it is a non-connection protocol. transmission between two computers is similar to sending mail: messages are sent from one computer to another, there is no clear connection between the two. UDP does not guarantee data transmission, and does not provide the function of re-sorting or re-request, so it is unreliable. Although the reliability of UDP limits its application scenarios, it has better transmission efficiency than TCP.

4. Application Layer

The application layer, presentation layer, and Session Layer correspond to the application layer in the Linux TCP/IP conceptual model. The application layer is at the top of the protocol stack, and its main task is application. It is generally visible. For example, you can use FTP (file transfer protocol) to transmit a file and request a connection to the target computer. During file transfer, part of the exchange between users and remote computers is visible. Common application layer protocols include HTTP, FTP, telnet, SMTP, And gopher. The application layer is the most critical layer for Linux network settings. The configuration document of the Linux Server mainly targets the protocols in the application layer. The functions and protocols of the TCP/IP model are shown in Table 1-2.

 

Table 1-2 Functions and protocols of the TCP/IP Model

 

Level name	Merit	Agreement
Network Interface (Host-to-net layer)	Responsible for actual data transmission, corresponding to the lower two layers of the OSI reference model	HDLC (Advanced Link Control Protocol) PPP (Point-to-Point Protocol) Slip (Serial Line Interface Protocol)
Internet Layer (Inter-network layer)	Responsible for inter-network addressing Data transmission, corresponding to the Layer 3 of the OSI reference model	IP (Internet Protocol) ICMP (Internet Control Message Protocol) ARP (Address Resolution Protocol) RARP (Reverse Address Resolution Protocol)
Transport Layer (Transport Layer)	Responsible for providing reliable transmission services, corresponding to the fourth layer of the OSI reference model	TCP (control transmission protocol) UDP (User Datagram Protocol)
Application Layer (Application Layer)	Responsible for implementing all functions related to the application, corresponding to the top three layers of the OSI reference model	FTP (file transfer protocol) HTTP (Hypertext Transfer Protocol) DNS (Domain Name Server Protocol) SMTP (Simple Mail Transfer Protocol) NFS (Network File System Protocol)

Note: The biggest difference between TCP/IP and OSI is that OSI is a theoretical network communication model, while TCP/IP is a actually running network protocol.