Well, it kind of does. Normally, the PXE network booting will use DHCP (or bootp or whatever) to fetch the boot image location, then it will fetch that boot image. Historically, that has worked this way:
1. bootp says boot image is at <ip address>/path/to/img
2. PXE network stack fetches that image via TFTP (which is awful)
3. PXE network stack boots that image
In most cases, the boot image would be a chainloader like pxelinux, and that would fetch a config file which told it the kernel path, the initrd path, and the commandline, and then the user could choose to boot that image, and then pxelinux would fetch the files via TFTP (which is still awful) and boot them.
In this new, HTTP-based case, we replace each instance of "TFTP" with "HTTP", which we can authenticate (ish), which we can easily firewall, which doesn't have weird compatibility issues, and so on.
Note that, before now, you could replace pxelinux with iPXE, and iPXE could fetch files via HTTP (which is awesome), but you still had to fetch iPXE and its config file via TFTP.
Note that TFTP is an unauthenticated, UDP-based, extremely limited protocol which has almost no support for anything but the most basic "get this file" or "take this file" functionality. Being able to replace it is a joy and a wonder.
1. bootp says boot image is at <ip address>/path/to/img 2. PXE network stack fetches that image via TFTP (which is awful) 3. PXE network stack boots that image
In most cases, the boot image would be a chainloader like pxelinux, and that would fetch a config file which told it the kernel path, the initrd path, and the commandline, and then the user could choose to boot that image, and then pxelinux would fetch the files via TFTP (which is still awful) and boot them.
In this new, HTTP-based case, we replace each instance of "TFTP" with "HTTP", which we can authenticate (ish), which we can easily firewall, which doesn't have weird compatibility issues, and so on.
Note that, before now, you could replace pxelinux with iPXE, and iPXE could fetch files via HTTP (which is awesome), but you still had to fetch iPXE and its config file via TFTP.
Note that TFTP is an unauthenticated, UDP-based, extremely limited protocol which has almost no support for anything but the most basic "get this file" or "take this file" functionality. Being able to replace it is a joy and a wonder.