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When a PXE workstation starts to boot up, it performs a DHCP discovery. During this process the workstation obtains IP information for itself and also information about the PXE boot servers that it can connect to. After completing the DHCP discovery process, the workstation contacts the boot server, downloads a file through Trivial File Transfer Protocol (TFTP), and executes the file.
The DHCP discovery process is more complex for a PXE workstation than it is for other DHCP-based products. During the DHCP discovery process the PXE workstation sends out a DHCP discovery request. Both the DHCP server and Proxy DHCP service need to receive and respond to this packet. The DHCP server will respond with IP address information for the client to use, and the Proxy DHCP server will respond with information about the boot server to use as well as the name of the boot file to download and execute.
The PXE workstation downloads the boot file that was specified during the DHCP discovery process by using either TFTP or multicast TFTP (MTFTP). In the case of the default Preboot Services implementation, the PXE workstation will always use TFTP because it speeds up the boot process of the workstation. The boot file (DINIC.SYS) is very small, so downloading it through MTFTP will not significantly reduce the network utilization of the product.
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