BuildImage

SMS 2003 OSD allows you to create an ISO boot image that you can burn to a blank disk. It doesn’t support using this as network boot media. There are various scripts (search, e.g. TechNet) that you explain how to create the Windows PE media; how to inject mass storage and network drivers, etc.; how to set up a TFTP root to make the ISO network-bootable.

BuildImage automates the bulk of this process. It also injects the PXE Lite Agent and associated components into the ISO image.

Web Service / Database / Admin Console

SMS 2003 OSD doesn’t include a way to control whether a machine will network boot or not. To get around this, the PXE Lite Server (specifically the DHCP part of it) contacts a web service to find out if it should respond to a boot request. The web service then looks in the OSDPlusPack database. All of this is controlled by the Admin Console.

PXE Lite Server

This is installed at the branch and handles DHCP and TFTP requests. It talks to the web service to find out if it should respond to a boot request. It also handles Nomad package location duties (since the PackageStatusRequest functionality wasn’t added until Nomad 3.x).

The PXE Lite Agent (see below) needs to contact the web service; the PXE Lite Server is responsible for web service discovery as well.

PXE Lite Agent / PXE Lite Reset

These are injected into the network boot ISO image. The agent talks to the database (via the web service) to find out which image that it should install on the PC. It then monkeys with the OSD environment block and hands control over to the SMS OSD components which get on with it.

Read the complete post at http://www.1e.com/techblog/post/2009/07/03/PXE-Lite-15-Components.aspx