It is the point at which network connections begin and end that is referred to as a port. A computer’s operating system manages ports, which are software-based. Ports are associated with specific processes or services. Emails, for example, go to a different port than webpages, even though both reach a computer over the same Internet connection.
How does a port number work?
Each port on a network-connection device is up to a number as part of the standardization process. Port 80 deliver for Hypertext Transfer Protocol (HTTP) messages, for example. IP addresses allow messages to go to and from specific devices, while port numbers allow specific services or applications to be on targert.
Network connections are more efficient through ports, how do they do this?
On the same network connection, data from and to computers can be of very different types. By using ports, computers are able to understand what to do with the data they receive.
Let’s say Bob uses the File Transfer Protocol (FTP) to transfer the MP3 audio recording to Alice. It would be impossible for Alice’s email application to understand the MP3 file data if Alice’s computer passed it to it. Alice’s computer can receive and store Bob’s file because he uses the port designated for FTP (port 21).
Although Alice’s computer uses the same WiFi connection as the MP3 sound file, it can simultaneously load HTTP webpages using port 80.
Ports are part of the network layer, aren’t they?
OSI is a conceptual model of how the Internet works. Different Internet services and processes are under a division into seven layers. The layers are as follows:
A port is a transport layer (layer 4) concept. Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) are the only transport protocols capable of indicating which port packets should be up to. Port numbers are present in the headers of TCP and UDP.
Protocols at the network layer, such as the Internet Protocol (IP), do not know what port is being under use.
A standard IP header does not indicate the port to which data packets should be up. Port numbers are not present in IP headers, only the destination IP address.
As network layer protocols are almost always up in conjunction with transport layer protocols, the inability to indicate the port at the network layer does not affect networking processes.
Testing software, which “pings” IP addresses using Internet Control Message Protocol (ICMP) packets, is affected by this change. ICMP allows network administrators to ping networked devices – but without the ability to ping specific ports, they are unable to test specific services.
My Traceroute, for instance, offers UDP packet support. As opposed to ICMP, which cannot specify a port, UDP can specify a port. Network administrators can test specific ports within networked devices by adding a UDP header to ICMP packets.
Is there a reason why firewalls block certain ports sometimes?
A firewall is a security system that blocks or allows network traffic according to a set of security rules. An Internet firewall is usually placed between a trusted network and an untrusted network. To protect their networks from online threats, office networks often use firewalls.
Attackers try to send malicious traffic to random ports in the hope that those ports are left “open,” allowing them to receive traffic. This action is similar to that of a car thief walking down the street and trying the doors of parked cars.
As a result, firewalls should be configured to block network traffic directed at most ports. The vast majority of available ports do not have any legitimate reason to receive traffic.
All ports are blocked by default by properly configured firewalls, with the exception of a few predetermined ports that are commonly used. The corporate firewall might allow internal employees to use ports 25 (email), 80 (web traffic), and 443 (web traffic), but block the rest of the 65,000+ ports.
Attackers sometimes use port 3389 to exploit vulnerabilities in the RDP protocol. A firewall may block port 3389 by default to prevent these attacks. Unless employees need to work remotely, such a rule has little impact on day-to-day business operations.
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