TCP/IP protocol concept, model, and protocol family

The concept, model, and Protocol family of TCP/IP Control Protocol/Internet Protocol are abbreviated as Transmission Control Protocol/Internet Protocol, also known as network communication Protocol, it is the most basic protocol of the Internet and the basis of the Internet international network. It consists of the IP protocol at the network layer and the TCP protocol at the transmission layer. TCP/IP defines how electronic devices connect to the Internet and how data is transmitted between them.

The protocol uses a layer-4 hierarchy. Each layer calls the network provided by its next layer to meet its own needs. In layman's terms: TCP is responsible for discovering transmission problems. When there is a problem, it sends a signal and requires a re-transmission until all data is securely and correctly transmitted to the destination. The IP address specifies an address for each computer on the Internet. In terms of protocol layered model, TCP/IP consists of four layers: network interface layer, network layer, transmission layer, and application layer. The TCP/IP protocol does not fully comply with the OSI Layer-7 Reference Model. The traditional Open System Interconnection Reference Model is a layer-7 abstract reference model of communication protocols, where each layer executes a specific task. This model aims to make various hardware communicate with each other at the same level. These seven layers are: physical layer, data link layer, network layer, transmission layer, Session Layer, presentation layer and application layer. The TCP/IP communication protocol uses a layer-4 hierarchy. Each layer calls the network provided by its next layer to meet its own needs. Www.2cto.com -------------------------- layer-4 Network Model

The physical layer of the network interface layer defines various features of physical media: 1. mechanical properties. 2. Electronic features. 3. features. 4. procedure features. The data link layer is responsible for receiving IP data packets and sending them over the network, or receiving physical frames from the network, extracting IP data packets, and handing them over to the IP layer. Www.2cto.com common interface layer protocols include Ethernet 802.3, Token Ring 802.5, X.25, Frame relay, HDLC, and ppp atm. The network layer is responsible for communication between adjacent computers. Its functions include three aspects. 1. process the packet sending request from the transport layer. After receiving the request, load the packet into an IP datagram, fill in the header, select the path to the sink, and then send the datagram to the appropriate network interface.
2. process the input datagram: first check its validity and then perform path search. If the datagram has arrived at the sink, remove the header and hand over the remaining part to the appropriate transmission protocol; if the datagram has not reached the destination, it is forwarded.
3. handle problems such as path, traffic control, and congestion. The network layer includes: IP (Internet Protocol) Protocol, ICMP (Internet Control Message Protocol) Protocol, ARP (Address Resolution Protocol) Protocol, and RARP (Reverse ARP) Protocol) the reverse address translation protocol. IP address is the core of the network layer. It encapsulates the next hop IP address through routing and then delivers it to the interface layer. IP datagram is a connectionless service. ICMP is a supplement to the network layer and can send packets back. Ping is used to check whether the network is smooth. The Ping Command sends an ICMP echo packet and tests the network by sending the echo relay. ARP is a forward Address Resolution Protocol. It uses known IP addresses to find the MAC address of the corresponding host. Www.2cto.com RARP is a Reverse Address Resolution Protocol, which determines the IP address through the MAC address. Such as diskless workstation and DHCP service. The transport layer provides communication between applications. Its functions include: 1. formatting information flows; 2. reliable transmission. To implement the latter, the transport layer protocol requires the receiving end to send back for confirmation, and if the group is lost, it must be resend. Transport layer protocols are mainly Transmission Control Protocol (TCP) and User Datagram protocol (UDP ). The application layer provides users with a set of common applications, such as email, file transfer access, and remote logon. Remote logon TELNET provides interfaces registered on other hosts in the network using the TELNET protocol. The TELNET session provides a character-based virtual terminal. File Transfer access FTP uses the FTP protocol to provide the file copy function between machines in the network. The application layer is generally a user-oriented service. Such as FTP, TELNET, DNS, SMTP, and POP3. FTP (File Transfer Protocol) is a File Transfer Protocol. FTP is used for uploading and downloading. The data port is 20 H and the control port is 21 H. Www.2cto.com
The Telnet service is a remote Logon Service. It uses port 23 and plain code for transmission, which provides poor confidentiality and convenience. DNS (Domain Name Service) is a Domain Name resolution Service that provides conversion between Domain names and IP addresses. SMTP (Simple Mail Transfer Protocol) is a Simple Mail transmission Protocol used to control the sending and transit of letters. POP3 (Post Office Protocol 3) is Post Office Protocol version 3rd used to receive emails. Layer functions in OSI: file transmission at the application layer of TCP/IP protocol family, email, file service, virtual terminal TFTP, HTTP, SNMP, FTP, SMTP, DNS, RIP, Telnet presentation layer data formatting, code Conversion, data encryption, no protocol, Session Layer release, or establish contact with other contacts, no protocol
The transport layer provides end-to-end interface TCP, And the UDP network layer selects Route IP addresses, ICMP, OSPF, BGP, IGMP, ARP, the RARP data link layer transmits the address frames and Error Detection Functions SLIP, CSLIP, PPP, MTU, ARP, and RARP. The physical layer transmits data ISO2110, IEEE802, on physical media in the form of binary data, the protocols at the network layer of IEEE 802.2 include IP, ICMP, and IGMP. because they contain IP protocol modules, they are the core of all TCP/IP-based networks. At the network layer, the IP module completes most of the functions. ICMP, IGMP, and other protocols that support IP addresses help IP addresses complete specific tasks, such as transmitting error control information and control messages between hosts and routers. The network layer is responsible for information transmission between hosts in the network.
The main protocols on the transport layer are TCP and UDP. Just as the network layer controls data transmission between hosts, the transport layer controls the data that will enter the network layer. The two protocols are the two methods for managing the data: TCP is a connection-based protocol, and UDP is the management method for the connectionless service.
The main disadvantages of the TCP/IP model are as follows: first, the model does not have a clear distinction between the region and the implementation. Second, the host-network layer of the TCP/IP model defines interfaces between the network layer and the data link layer, which is not a layer in the general sense. The difference between the host-network layer and the interface layer is very important, the TCP/IP model does not distinguish them.