Key network protocols with transport, ports, and purpose.
| Protocol | Transport + Port | Purpose |
|---|---|---|
| HTTPS | TCP 443 | Encrypted web traffic |
| HTTP | TCP 80 | Unencrypted web traffic |
| FTP | TCP 20, 21 | File transfer, control + data |
| SSH | TCP 22 | Secure remote login, tunnels |
| Telnet | TCP 23 | Legacy unencrypted remote login |
| SMTP | TCP 25, 587 | Sending and relaying email |
| DNS | UDP/TCP 53 | Name resolution |
| DHCP | UDP 67, 68 | Automatic IP assignment |
| TFTP | UDP 69 | Simple file transfer, PXE boot |
| SNMP | UDP 161, 162 | Device monitoring and traps |
| LDAP | TCP 389 | Directory lookups, auth |
| SMB | TCP 445 | Windows file/printer sharing |
| NFS | TCP 2049 | Unix file sharing |
| RDP | TCP 3389 | Windows remote desktop |
| SIP | TCP/UDP 5060 | VoIP call signaling |
| BGP | TCP 179 | Inter-domain routing |
| OSPF | IP 89 | Interior link-state routing |
| ICMP | IP 1 | Ping, errors, diagnostics |
| ARP | Link layer | IP-to-MAC resolution on LAN |
Transport shows what carries the protocol: TCP for reliability, UDP for speed, IP numbers for network-layer protocols, link layer for ARP.
DNS → UDP/TCP 53 → name resolution.UDP 53 for fast queries, TCP 53 for large answers and zone transfers.
BGP routes between autonomous systems on the internet; OSPF routes inside one network.