“Transport layer” [OSI Model].
TCP – Transmission Control Protocol is used for transport data between processes runs on 2 different devices. It works in the client-server mode. As opposed to UDP, the TCP guarantees the delivery of all data packets in sequence and without duplicates. We can distinguish 3 phases of this process: initiation connection – data transfer – termination.
TCP works in a three-way handshake during initiation connection. SYN (Synchronize) / SYN-ACK (Synchronize – Acknowledgment) / ACK (Acknowledgment)
Main features during data transfer: arranged in segments – avoid congestion – error-free transfer – retransmission of lost packets.
The connection termination uses a four-way handshake.
UDP – User Datagram Protocol has the same role to fulfil as TCP but in a different way. Data is sent in a stream without error correction can be sent to multi destinations at the same time (multicasting). The main advantage over the UDP is speed. Mainly used in online gaming, video streaming, VoIP, DHCP.
| Port number | TCP / UDP | Name | Description |
|---|---|---|---|
| 13 | TCP & UDP | daytime | Daytime protocol |
| 20 | TCP | ftp-data | File Transfer Protocol. Data transfer. |
| 21 | TCP | ftp | File Transfer Protocol. Command. |
| 22 | TCP | ssh | Secure Shell |
| 23 | TCP | telnet | Telnet. Unencrypted text communications |
| 25 | TCP | smtp | Simple Mail Transfer Protocol |
| 53 | TCP & UDP | domain | Domain Name System (DNS) |
| 67 | UDP | dhcps | DHCP Server |
| 68 | UDP | dhcpc | DHCP Client |
| 69 | TCP | TFTP | Trivial File Transfer Protocol |
| 80 | TCP | http | Hypertext Transfer Protocol |
| 110 | TCP | pop3 | Post Office Protocol (e-mail communication) |
| 123 | UDP | ntp | Network Time Protocol. Time synchronization |
| 137 | TCP & UDP | netbt | NetBios Name Service |
| 143 | TCP | imap | Internet Message Access Protocol (e-mail communication) |
| 161 | UDP | snmp | Simple Network Management Protocol |
| 162 | UDP | snmp-trap | Simple network management protocol trap |
| 389 | TCP | ldap | Lightweight Directory Access Protocol |
| 427 | TCP & UDP | slp | Service Location Protocol |
| 443 | TCP & UDP | https | Hypertext Transfer Protocol Secure |
| 445 | TCP | smb | Server Message Block. Microsoft-DS |
| 548 | TCP | afp | Apple Filing Protocol |
| 587 | TCP | smtps | secure Simple Mail Transfer Protocol |
| 636 | TCP | ldaps | Lightweight Directory Access Protocol TLS/SSL |
| 993 | TCP | imaps | Internet Message Access Protocol SSL/TLS |
| 995 | TCP | pop3s | Post Office Protocol SSL/TLS |
| 3306 | TCP | mysql | MySQL Database |
| 3389 | TCP | rdp | Microsoft Remote Desktop Protocol |
| 5060 | UDP | sip | VoIP |
| 5061 | UDP | sip | VoIP |
| 5938 | TCP & UDP | teamview | Team Viewer Remote Desktop Protocol |
| 8200 | TCP | goto | GoToAssist (LogMeIn) |
| 23399 | TCP & UDP | skype | Skype |
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