Some application layer protocol
The application layer is present at the top of the OSI model. The users interact through this layer and provides services to the user.
Some application layer protocols as follows:
| Protocols | Details | Port | Command |
|---|---|---|---|
| TELNET | Telnet stands for the TELetype NETwork. TELNET helps in terminal emulation and allows Telnet-clients to access the resources of the Telnet-server. Used for managing files on the internet. Used for the initial setup of devices like switches. | 23 | telnet [\\RemoteServer] |
| FTP | FTP stands for file transfer protocol. It can facilitate file transfer between any two machines. But FTP is not just a protocol but it is also a program. | 20 for data and 21 for control | ftp machinename |
| TFTP | TFTP stands for Trivial File Transfer Protocol. It is a simplified version of FTP. | 69 | tftp [ options... ] [host [port]] [-c command] |
| SMTP | SMTP stands for Simple Mail Transfer Protocol. It is a part of the TCP/IP protocol. SMTP moves our email on and across networks. It works with Mail Transfer Agent (MTA) to send our communication to the right computer and email inbox. | 25 | MAIL FROM:<mail@abc.com? |
| SNMP | SNMP stands for Simple Network Management Protocol. It gathers data by polling the devices on the network from a management station at fixed or random intervals, requiring them to disclose certain information. | 161(TCP) and 162(UDP) | snmpget -mALL -v1 -cpublic snmp_agent_Ip_address sysName.0 |
| DNS | DNS stands for Domain Name System. When we use domain name, a DNS service translates the name into the corresponding IP address. For example, the domain name xyz.com translate to 108.105.222.7 | 53 | ipconfig /flushdns |
| DHCP | DHCP stands for Dynamic Host Configuration Protocol (DHCP). It gives IP addresses to hosts. There is a lot of information a DHCP server can provide to a host when the host is registering for an IP address with the DHCP server. | 67, 68 | clear ip dhcp binding {address | * } |
| POP | POP stand for Post Office Protocol. The POP-3 is a simple mail retrieval protocol used by User Agents (client email software) to retrieve mails from mail server. | 110 | |
| HTTP | HTTP stand for Hyper Text Transfer Protocol. It is the foundation of World Wide Web. HTTP works on client server model. When any user wants to access any HTTP page on the internet then client machine at user end initiates a TCP connection to server. | 80 | |