Application layer protocols include: 1. Domain name system DNS protocol, FTP file transfer protocol, telnet remote terminal protocol, HTTP hypertext transfer protocol, SMTP email protocol, POP3 email reading protocol, and Telnet remote login protocol , SNMP simple network management protocol, etc.
The application layer protocol defines how application processes running on different end systems transfer messages to each other.
Application Layer Protocol
1. DNS: Domain Name System DNS is a naming system used by the Internet to convert machine names that are easy for people to use into IP addresses.
Currently top-level domain name TLDs are divided into three categories: national top-level domain names nTLDs; general top-level domain names gTLDs; infrastructure domain names
Domain name servers are divided into four types: root domain name servers; top-level domain name servers ;Local domain name server; authority domain name server.
2. FTP: File Transfer Protocol FTP is the most widely used file transfer protocol on the Internet. FTP provides interactive access, allows customers to specify file types and formats, and allows files to have access rights. FTP is different from TCP.
3. Telnet Remote Terminal Protocol: Telnet is a simple remote terminal protocol, which is also the official standard of the Internet. Also known as the terminal emulation protocol.
4. HTTP: Hypertext Transfer Protocol is a transaction-oriented application layer protocol. It is an important foundation for the reliable exchange of files on the World Wide Web. http uses connection-oriented TCP as the transport layer protocol to ensure reliable transmission of data.
5. Email protocol SMTP: Simple Mail Transfer Protocol. SMTP specifies how information should be exchanged between two SMTP processes that communicate with each other. There are three stages of SMTP communication: connection establishment, email transmission, and connection release.
6. POP3: Mail reading protocol, POP3 (Post Office Protocol 3) protocol is usually used to receive emails.
7. Remote login protocol (Telnet): used to implement remote login function.
8. SNMP: Simple Network Management Protocol. It consists of three parts: SNMP itself, management information structure SMI and management information MIB. SNMP defines the format of packets exchanged between management stations and agents. SMI defines general rules for naming object types and encoding objects and object values. MIB creates named objects in managed entities and specifies types.
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