Transport Layer protocols leverage what is known as a port number in order to associate the particular communication with a specific application on a device. Port numbers compose part of a socket which is used to allow applications on particular hosts to communicate with each other. Port numbers are used by the following Transport Layer protocols:
- Transmission Control Protocol (TCP)
- User Datagram Protocol (UDP)
- Stream Control Transmission Protocol (SCTP)
- Datagram Congestion Control Protocol (DCCP)
There are other Transport Layer protocols in use, but these don't leverage port numbers.
The range of port numbers used by these protocols is divided into three categories:
- Well-known Ports (0 to 1023): These port numbers are used by system processes or services that provide widely used types of network services, like HTTP (port 80), HTTPS (port 443), FTP (port 21), etc.
- Registered Ports (1024 to 49151): These ports are assigned by IANA for specific services, and applications can use these ports with IANA's registration to avoid conflicts.
- Dynamic or Private or Ephemeral Ports (49152 to 65535): These are ports that can be freely used dynamically since they cannot be registered with IANA. This range is used for private or customized services for temporary purposes. This is the range typically used by NAT as well as for automatic allocation.
Links:
https://networklessons.com/cisco/ccna-routing-switching-icnd1-100-105/introduction-to-tcp-and-udp
https://networklessons.com/cisco/ccna-routing-switching-icnd1-100-105/tcp-header
FAQs
What is a port number? A port number is a way to identify a specific process to which an internet or other network message is to be forwarded when it arrives at a server. All network-connected devices come equipped with standardized ports that have an assigned number.
What is the port number for transport layer security? ›
The TLS/SSL port is 443, HTTPS, and employs TLS/SSL certificates to safeguard port communications. HTTP is the unsecure protocol port (port 80).
Why port number limited to 65535? ›
Each bit has 0 or 1, so total 2 combinations. For 16 bits, there will be 2^16 =65536 combinations. Since ports can start from 0, so it will max value 65535.
What does the transport layer use port numbers to identify? ›
DNS is a protocol that automatically provides a computer with its IP address configuration. The Transport layer uses port numbers to identify the source and destination Application-layer protocol of the data that it contains.
What is port 443 in the transport layer? ›
Port 443 works by using a cryptographic protocol called TLS (Transport Layer Security). TLS is the successor to SSL (Secure Sockets Layer), and it provides a secure channel between two machines or devices operating over the internet or an internal network.
What is port 1024 to 49151? ›
Ports with numbers 0–1023 are called system or well-known ports; ports with numbers 1024-49151 are called user or registered ports, and ports with numbers 49152-65535 are called dynamic, private or ephemeral ports.
How do I find my port number? ›
How to find your port number on Windows
- Type “Cmd” in the search box.
- Open “Command Prompt.”
- Enter the netstat -a command to see your port numbers.
Originally, the Simple Mail Transfer Protocol (SMTP) used port 25. Today, SMTP should instead use port 587 — this is the port for encrypted email transmissions using SMTP Secure (SMTPS). Port 465 is also used sometimes for SMTPS.
What is port 80 and 443? ›
Port 80 allows HTTP protocol means the information remains in plain text between the browser and the server, while Port 443 allows HTTPS protocol means all the information travels between the server and the browser remains encrypted.
What are ports 1024 65535 used for? ›
Ports 1,024–65,535 are called registered ports; these numbers are not controlled by IANA and can be used by user processes or applications. Some of these are traditionally used by specific applications (for example, SQL uses port 1,433) and could be of interest to hackers.
In older computers with processors having a 16-bit address bus such as the MOS Technology 6502 popular in the 1970s and the Zilog Z80, 65535 (FFFF16) is the highest addressable memory location, with 0 (000016) being the lowest. Such processors thus support at most 64 KiB of total byte-addressable memory.
What is port 0 65535? ›
Port numbers come in the range of 0 to 65535. Numbers 1–1023 are assigned to services, and 1024 to 65535 are ephemeral ports used to identify a source. Port 0 is assigned by the Internet Assigned Numbers Authority (IANA) as “reserved.”
What number is the transport layer? ›
Layer 4 of the OSI model, also known as the transport layer, manages network traffic between hosts and end systems to ensure complete data transfers.
What are TCP port numbers? ›
Each TCP port is assigned a unique number ranging from 0 to 65535. These ports are categorized into three ranges: well-known ports (0-1023), registered ports (1024-49151), and dynamic or private ports (49152-65535).
What is the TCP port 7070? ›
The TCP port 7070 is used by the client to initiate a conversation with an external RealServer, to authenticate the player to the server, and to pass control messages during playback (e.g., pausing or stopping the audio stream).
Is port number TCP or UDP? ›
Yes, TCP and UDP ports are different, but they sometimes use the same port number. For example, UDP/53 and TCP/53 are both used for DNS, but they are different connection types. TCP ports comply with transmission control protocols, while UDP ports comply with user datagram protocols.
What is my port number? ›
Type “Cmd” in the search box. Open “Command Prompt.” Enter the netstat -a command to see your port numbers.
What is the port number for FTP? ›
Port numbers 21 and 20 are used for FTP.
Port 21 is used to establish the connection between the 2 computers (or hosts) and port 20 to transfer data (via the Data channel). File transfer is among the most frequently used TCP/IP applications and it accounts for a lot of the network traffic on the Internet.
