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What are PAT and NAPT?
When it comes to Internet connectivity, PAT (Port Address Translation) and NAPT (Network Address Port Translation) are two essential concepts to understand. These techniques play a crucial role in enabling multiple devices to connect to the Internet through a single public IP address.
PAT – Port Address Translation
PAT, also known as NAT overload, is a form of network address translation that involves translating IP addresses and ports. It allows a router to map multiple private IP addresses used within a local network to a single public IP address. PAT operates at the transport layer of the TCP/IP protocol stack, specifically translating the TCP/UDP port numbers of outbound traffic.
Here’s how it works: when a device from the local network initiates a connection to the Internet, the source IP address and port are translated to the router’s public IP address and a unique port number. The router keeps track of the port mappings so that when the response comes back, it can correctly forward the incoming traffic to the appropriate device on the local network.
PAT provides a solution for conserving public IP addresses and is widely used in home and small office networks.
NAPT – Network Address Port Translation
NAPT, also known as IP masquerading or NAT overload, is an extension of PAT. While PAT primarily focuses on translating ports, NAPT involves translating both the IP addresses and the transport layer port numbers.
With NAPT, a router can handle multiple private IP addresses from different local networks and translate them into a single public IP address. This allows devices from multiple local networks to share a single public IP address simultaneously.
Additionally, NAPT keeps track of the transport layer session, allowing multiple devices in different local networks to establish simultaneous connections to the same remote destination using the same port numbers.
NAPT is commonly used in larger networks and is crucial in scenarios where there are multiple private networks, such as in a business environment or a public Wi-Fi hotspot.
In conclusion, PAT and NAPT are both techniques used in network address translation to enable connectivity of multiple devices through a single public IP address. PAT focuses on translating ports, while NAPT extends the translation to both IP addresses and port numbers, allowing for the sharing of a single public IP address among multiple local networks. Understanding these concepts is essential for comprehending how networks handle the increasing demand for internet connectivity.
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