What is the purpose of Network Address Translation (NAT)?

Network Address Translation (NAT) serves the primary purpose of translating private IP addresses used within a local network to a public IP address that can be used on the internet. This is essential for enabling multiple devices within a private network to share a single public IP address when accessing external networks, thereby efficiently managing IP address usage and enhancing security.

When devices on a local network communicate with external systems, NAT modifies the headers of outgoing packets to replace the private IP addresses with the public IP address assigned to the NAT device. This way, the devices can send and receive traffic through the internet while being shielded from direct exposure to external networks. When responses come back, NAT recognizes the traffic and forwards the packets back to the correct internal devices based on the original requests.

This process helps in extending the life of IPv4 addresses, which are limited in number and promotes a level of security, as external entities cannot directly reach devices with private IP addresses. Thus, option B accurately captures the essence of NAT's functionality.