What function does Network Address Translation (NAT) serve?

Network Address Translation (NAT) serves the critical function of translating public IP addresses to private IP addresses. This is essential in environments where multiple devices need to share a single public IP address to access the internet. NAT helps in conserving the limited number of available public IP addresses and enhances security by allowing internal devices to remain hidden from external networks.

When a device from a private network communicates with an external server, NAT changes that device's private IP address into a public IP address for the duration of the communication. When the response returns, NAT translates the public IP address back into the original private IP address, ensuring that the correct internal device receives the data. This process adds a layer of security because external entities cannot directly interact with devices on the internal network, which are identified only by their private IP addresses.

The other options do not accurately describe the primary function of NAT. For instance, while it supports network connectivity, it does not inherently focus on securely connecting multiple networks. It also does not translate internal networking protocols, nor does it secure data during transmission. Its main purpose is specifically the IP address translation to facilitate communication while maintaining the internal network's privacy.