Domain Name Server: DNS is a host name to IP address translation service. DNS is a distributed database implemented in a hierarchy of name servers. It is an application layer protocol for message exchange between clients and servers.
Dynamic Host Configuration Protocol(DHCP) is an application layer protocol which is used to provide:
Subnet Mask (Option 1 – e.g., 255.255.255.0)
Router Address (Option 3 – e.g., 192.168.1.1)
DNS Address (Option 6 – e.g., 8.8.8.8)
Vendor Class Identifier (Option 43 – e.g., ‘unifi’ = 192.168.1.9 ##where unifi = controller)
Simple Network Management Protocol (SNMP) : SNMP is an application layer protocol which uses UDP port number 161/162.SNMP is used to monitor network, detect network faults and sometimes even used to configure remote devices.
Simple Mail Transfer Protocol (SMTP): SMTP is an application layer protocol. The client who wants to send the mail opens a TCP connection to the SMTP server and then sends the mail across the connection. The SMTP server is always on listening mode. As soon as it listens for a TCP connection from any client, the SMTP process initiates a connection on that port (25). After successfully establishing the TCP connection the client process sends the mail instantly.
File Transfer Protocol (FTP): File Transfer Protocol(FTP) is an application layer protocol which moves files between local and remote file systems. It runs on the top of TCP, like HTTP. To transfer a file, 2 TCP connections are used by FTP in parallel: control connection and data connection.
Hypertext Transfer Protocol (HTTP): is an application-level protocol that uses TCP as an underlying transport and typically runs on port 80. HTTP is a stateless protocol i.e. server maintains no information about past client requests.
