What does the PXE protocol allow for during system boot?

The PXE (Preboot Execution Environment) protocol is designed specifically for network booting. It allows computers to boot up and load an operating system or software directly from a network interface, rather than from local storage devices like hard drives or USB drives. This is particularly useful in environments where multiple systems need to be deployed or maintained without the need for physical media on each machine.

With PXE, a client machine can send a request to a PXE server during the boot process. The server then provides the necessary files, such as an operating system image and boot configuration, enabling the system to start without requiring local media. This capability supports network installations, diskless workstations, and other configurations where remote management is essential.

In contrast, local hard drive booting, booting from USB, and virtual machine booting involve specific types of hardware or locally connected devices. PXE operates distinctly by leveraging network resources to initiate the boot process, which is why the correct answer pertains to network booting.