1、HTTP？
The default TCP 80 port is used for browsers to browse web pages, but the content of web pages is plain text, which is easy to be tampered with, hijacked and leaked.
HTTPS？
S in HTTPS stands for security, which works on TCP port 443 by default, but there is a secure encryption intermediate layer between the ordinary HTTP and TCP layers, called SSL (Secure Sockets Layer). It is used to encrypt the webpage content based on HTTP, which is not easy to be tampered with and hijacked, and the webpage content is confidential. At present, it is widely used in online banking and other industries. However, there are security loopholes, which are easy to be deceived and attacked by middlemen. ?
3、SMTP？
Application layer protocol of mail sending based on TCP. ?
4、POP3？
Application layer protocol of mail receiving based on TCP. ?
5、DNS？
The application layer protocol based on UDP/TCP is used to resolve domain names and IP addresses. ?
6、DHCP？
Application layer protocol based on UDP, which allows the host to dynamically obtain parameters such as IP address, default gateway and DNS server. ?
7. CIFS (Common Internet File System)?
Most people are not familiar with this agreement. In fact, many people have used it. It is an application layer protocol based on TCP enjoyed by Windows files. ?
8. NFS (Network File System)?
This is used for Unix/Linux file sharing, based on UDP/TCP protocol. ?
9. NTP (Network Time Protocol)?
Application layer clock synchronization protocol based on UDP. ?
10, SIP (Session Initiation Protocol)?
IP telephone signaling protocol, IETF protocol standard, application layer protocol based on TCP/UDP. ?
1 1、H.323？
It is also an IP telephone signaling protocol, an ITU protocol standard of the International Telecommunication Union, and an application layer protocol based on TCP/UDP. ?
12, RTP (real-time protocol)?
IP multimedia phone used to transmit voice, text, video and other fluids is based on UDP application layer protocol.
At present, there are several protocols that can be thought of, and some application-layer protocols, such as SNMP and TFTP, are generally used for network management and file transfer, and are rarely used by ordinary people. ? Because it does not provide security, application layer protocols such as FTP and telnet are used less and less, and s FTP and SSH are used instead.