Transport protocol port number information (TCP, UDP, DCCP, and SCTP)

General info

IANA is a standards organization that controls global IP address allocation, autonomous system number (ASN) allocation, Domain Name System (DNS) root zone managegement, media types (MIME type) and other Internet Protocol related symbols. Currently IANA ia a function of Internet Corporation for Assigned Names and Numbers (ICANN) organization. They delegates allocations of IP address blocks to Regional Internet Registries (RIRs).

General info

Service names and port numbers are used to distinguish between different services that run over transport protocols such as TCP, UDP, DCCP, and SCTP.

Service names are assigned on a first-come, first-served process, as documented in [RFC6335].

Port numbers are assigned in various ways, based on three ranges:

  • System Ports (0-1023) (assigned by IANA using the "IETF Review" or "IESG Approval" procedures)
  • User Ports (1024-49151) (assigned by IANA using the "IETF Review" process, the "IESG Approval" process, or the "Expert Review" process)
  • Dynamic and/or Private Ports (49152-65535) (are not assigned)

Reference document: RFC6335

Here are some interesting trivia facts about Network Port numbers
Well-Known Ports

Network ports are numbered entities used to identify different services running on a computer. Well-known ports are those ranging from 0 to 1023, which are assigned to commonly used services. For example, port 80 is typically used for HTTP (Hypertext Transfer Protocol), while port 443 is used for HTTPS (HTTP Secure).

Dynamic vs. Static Port Allocation

Ports can be allocated dynamically or statically. Dynamically allocated ports are assigned by the operating system to applications as needed, typically from a range of available ports (e.g., 1024 to 65535). Static port allocation involves manually assigning specific ports to applications or services, ensuring consistent communication on those ports.

Port Scanning

Port scanning is a technique used to identify open ports on a target system. It involves sending network requests to various port numbers and analyzing the responses to determine which ports are open and accessible. Port scanning is commonly used for network reconnaissance, security auditing, and vulnerability assessment.

IANA Port Number Registry

The Internet Assigned Numbers Authority (IANA) maintains the official registry of port numbers and their associated services. This registry provides standardized port assignments and helps ensure interoperability and consistency across different network devices and protocols.

Common Port Numbers
  • Port 21 is used for FTP (File Transfer Protocol), which is a standard network protocol used for transferring files between a client and a server on a computer network. FTP operates in two modes: active and passive, and port 21 is used for control messages in both modes.
  • Port 22 is the default port for SSH (Secure Shell), which is a cryptographic network protocol used for secure remote access to a computer or server over an unsecured network. SSH provides encrypted communication sessions for secure command-line, remote command execution, and other network services.
  • Port 25 is used for SMTP (Simple Mail Transfer Protocol), which is the standard protocol for sending email messages between servers. SMTP is used by mail servers to relay email messages over the internet, and port 25 is the default port for SMTP server-to-server communication.
  • Port 53 is used for DNS (Domain Name System), which is a hierarchical and decentralized naming system for computers, services, or other resources connected to the internet or a private network. DNS resolves domain names to IP addresses and vice versa, enabling users to access websites using human-readable domain names.
  • Port 67/68 are used for DHCP service. DHCP (Dynamic Host Configuration Protocol) uses UDP (User Datagram Protocol) ports 67 and 68 for communication between DHCP clients and DHCP servers. Port 67 is used by DHCP servers to receive DHCP discover and request messages from clients, while port 68 is used by DHCP clients to send DHCP discover, request, and renewal messages to servers. DHCP is responsible for dynamically assigning IP addresses, subnet masks, default gateways, DNS server addresses, and other network configuration parameters to devices on a network, simplifying network administration and configuration
  • Port 80 is the default port for HTTP (Hypertext Transfer Protocol), which is used for serving web pages over the World Wide Web. When you enter a website address in your web browser without specifying a port number, it assumes port 80 by default.
  • Port 110 is used for POP3 (Post Office Protocol version 3), which is a standard protocol for receiving email messages from a remote server to a local email client. POP3 allows users to download their email messages to their local computer or device for offline access.
  • Port 143 is used for IMAP (Internet Message Access Protocol), which is a standard protocol for accessing and retrieving email messages from a remote mail server. IMAP allows users to manage their email messages on the server, including viewing, organizing, and deleting messages, without downloading them to their local device.
  • Port 443 is the default port for HTTPS (HTTP Secure), which is the secure version of HTTP. It's used for secure communication over the internet, particularly for transmitting sensitive data such as login credentials and payment information.
  • Port 993 is the default port for IMAPS (IMAP Secure), which is the secure version of IMAP. IMAPS encrypts communication between the email client and the mail server using SSL/TLS (Secure Sockets Layer/Transport Layer Security) encryption, providing enhanced security for email communication.
  • Port 465 was initially designated for SMTPS (SMTP Secure), which was the secure version of SMTP using SSL/TLS encryption. However, it's now deprecated in favor of using SMTP over TLS on the standard SMTP port (25 or 587). Some legacy systems may still use port 465 for SMTPS, but it's not recommended for new deployments.
  • Port 587 is the default port for SMTP submission, which is used by email clients to submit outgoing email messages to a mail server for delivery. SMTP submission typically requires authentication and encryption using STARTTLS (an extension of SMTP for upgrading a plain text connection to a secure TLS connection).
Port Forwarding

Port forwarding, also known as port mapping, is a networking technique that redirects traffic from one network port on a router or firewall to another network port on a different device within the local network. It's often used to enable remote access to services hosted on internal network devices, such as web servers or gaming consoles.

UDP and TCP Ports

Ports are associated with specific transport layer protocols, such as UDP (User Datagram Protocol) and TCP (Transmission Control Protocol). While TCP ports are used for connection-oriented communication, UDP ports are used for connectionless communication. Each protocol has its own range of port numbers.

Non-Standard Ports

Some applications may use non-standard ports, meaning they operate on port numbers outside the well-known or commonly used ranges. These ports can be configured by users or developers based on their specific requirements but may require additional configuration to ensure proper network connectivity and security.

These trivia facts highlight some of the most commonly used network port numbers and their associated protocols, which play a crucial role in facilitating various internet services and communication protocols. Fascinating, isn’t it?