What Are Ports in Networking?

Usually, the Network Port concept is challenging to understand. In networking, it is a communication endpoint used to connect an external device to the computer. When there is a requirement to set up remote access for your IP Cameras, the network port comes into the picture. Routers are dependent on ports to route data to access your camera and share between multiple devices. Let us discuss more network ports.  

What are Networking Ports?

A port is a virtual place at the software level in an operating system that is used for the identification of the types of network service. It is where the connection with a network begins and ends. 

All ports have their unique process. The role of ports in a computer is to identify the type of traffic from the network. For example, the emails sent or received on a device use a different port than a website accessed through browsers, even when the internet connection in use is the same.  

What is a port number?

All network-connected devices use the same ports, and each port has a unique number. The majority of ports are set aside for specific protocols; for instance, port 80 is the designated location for all HTTP transmissions. Port numbers enable the targeting of particular services or applications within those devices, whereas IP addresses enable messages to move to and from specific devices.

How do ports work in networking?

A network port handles multiple transmission requests through a single physical network on a computer. For file transfer, a particular number is assigned, termed as Port Number.
A port has three main applications in computer networking, as mentioned below:

  • Firstly, in computer networking, a port is a software-defined number related to a Network Protocol. This number is used to transmit and receive communication for a particular service.
  • Secondly, computer hardware is a socket where peripheral devices can plugin.
  • Lastly, when a piece of software needs to be converted to run on another device or Operating system, a port is used as computer software.  

Are ports part of the network layer?

The OSI model is a conceptual model of how the Internet works. It divides different Internet services and processes into 7 layers. These layers are:

osi model 7 layers

Ports are a transport layer (layer 4) concept. Only a transport protocol such as the Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) can indicate which port a packet should go to. TCP and UDP headers have a section for indicating port numbers. Network layer protocols ā€” for instance, the Internet Protocol (IP) ā€” are unaware of what port is in use in a given network connection. In a standard IP header, there is no place to indicate which port the data packet should go to. IP headers only indicate the destination IP address, not the port number at that IP address.

Due to the fact that network layer protocols are usually always used in conjunction with transport layer protocols, the inability to specify the port at the network layer typically has little effect on networking processes. However, this does have an effect on the functionality of testing software, which is software that uses ICMP packets to “ping” IP addresses. Network administrators cannot test specific services in networked devices without the ability to ping specific ports, even though ICMP is a network layer protocol that can ping networked devices.

Some ping software, such as My Traceroute, offers the option to send UDP packets. UDP is a transport layer protocol that can specify a particular port, as opposed to ICMP, which cannot specify a port. By adding a UDP header to ICMP packets, network administrators can test specific ports within a networked device.

Why do firewalls sometimes block specific ports?

A firewall is a security system that blocks or allows network traffic based on a set of security rules. Firewalls usually sit between a trusted network and an untrusted network; often the untrusted network is the Internet. For example, office networks often use a firewall to protect their network from online threats.

Some hackers try to send malicious traffic to arbitrary ports in the hopes that those ports have been left “open,” which means they can accept traffic. This behavior resembles that of a car burglar who walks down the street and taps on the doors of parked cars in the hopes that one is unlocked. Because of this, firewalls ought to be set up to restrict network traffic aimed at the majority of open ports. The vast majority of the open ports should not be receiving traffic for any reason.

Properly configured firewalls block traffic to all ports by default except for a few predetermined ports known to be in common use. For instance, a corporate firewall could only leave open ports 25 (email), 80 (web traffic), 443 (web traffic), and a few others, allowing internal employees to use these essential services, then block the rest of the 65,000+ ports.

As a more specific example, attackers sometimes attempt to exploit vulnerabilities in the RDP protocol by sending attack traffic to port 3389. To stop these attacks, a firewall may block port 3389 by default. Since this port is only used for remote desktop connections, such a rule has little impact on day-to-day business operations unless employees need to work remotely. 

What are the different port numbers?

There are 65,535 possible port numbers, although not all are in common use. Some of the most commonly used ports, along with their associated networking protocol, are:

  • Ports 20 and 21: File Transfer Protocol (FTP). FTP is for transferring files between a client and a server.
  • Port 22: Secure Shell (SSH). SSH is one of many tunneling protocols that create secure network connections.
  • Port 25: Simple Mail Transfer Protocol (SMTP). SMTP is used for email.
  • Port 53: Domain Name System (DNS). DNS is an essential process for the modern Internet; it matches human-readable domain names to machine-readable IP addresses, enabling users to load websites and applications without memorizing a long list of IP addresses.
  • Port 80: Hypertext Transfer Protocol (HTTP). HTTP is the protocol that makes the World Wide Web possible.
  • Port 123: Network Time Protocol (NTP). NTP allows computer clocks to sync with each other, a process that is essential for encryption.
  • Port 179: Border Gateway Protocol (BGP). BGP is essential for establishing efficient routes between the large networks that make up the Internet (these large networks are called autonomous systems). Autonomous systems use BGP to broadcast which IP addresses they control.
  • Port 443: HTTP Secure (HTTPS). HTTPS is the secure and encrypted version of HTTP. All HTTPS web traffic goes to port 443. Network services that use HTTPS for encryption, such as DNS over HTTPS, also connect at this port.
  • Port 500: Internet Security Association and Key Management Protocol (ISAKMP), which is part of the process of setting up secure IPsec connections.
  • Port 3389: Remote Desktop Protocol (RDP). RDP enables users to remotely connect to their desktop computers from another device.

The Internet Assigned Numbers Authority (IANA) maintains the full list of port numbers and protocols assigned to them.

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