9. Application layer protocols

9.8. Summary

The application layer protocols described in this section are only a small part of the overall list of application layer protocols available. There are many other services on a computer network, each running on a different protocol. It is hard to list them here, so the most popular and commonly used ones are listed: 

Protocol

Description

Port

HTTP

Hypertext transfer protocol

80

HTTPS

Encrypted HTTP protocol using SSL or TLS protocols

443

POP3

Protocol for the receipt of mail

110 (encrypted 995)

IMAP

Mail receiving protocol to manage folders in the mailbox

143 (encrypted 993)

SMTP

Mail sending protocol

25 (encrypted 465 or 587)

FTP

File transfer protocol

21 (commands) and 20 (files)

FTPS

Encrypted FTP protocol

990

TELNET

Terminal connection protocol

23

SSH

Encrypted terminal connection protocol

22

DNS

Protocol for changing domain names to IP addresses

53

DHCP

Protocol for automatic configuration of hosts on the network

67 and 68 (IPv6 - 546 and 547)

LDAP

Directory services protocol (e.g. AD in WS)

389 (coded 639)

SNMP

Network equipment configuration protocol

161

MySQL

Database management system

3306

PostgreSQL

Database management system

5432