- CCENT-CCNA：ICND1 100-105 Certification Guide
- Bekim Dauti
- 180字
- 2021-08-27 18:21:54
Application layer protocols
The application layer (Layer 7) is responsible for interacting with the operating system or application whenever the user decides to transmit data with their computer over a computer network or the internet. To better understand the functionality of the application layer, instead of thinking about applications, instead try thinking about the processes that enable applications to utilize network services. The term data is used to represent the PDU at this layer, as shown in Figure 2.11. In this layer, the following communication protocols operate:
- HTTP operates on port 80
- HTTPS operates on port 443
- SMTP operates on port 25
- POPv3 operates on port 110
- IMAPv4 operates on port 143
- FTP operates on port 21
- DNS operates on port 53
- DHCP operates on port 67 for server, and port 68 for client
- SSH operates on port 22
- Telnet operates on port 23
An application port is a logical endpoint that enables applications from your computer to communicate with applications on other computers. You can learn more about the well-known communication protocols and their corresponding port numbers at: http://www.meridianoutpost.com/resources/articles/well-known-tcpip-ports.php.