PXE-Booting or Etherbooting usually is a quite complex thing that usually involves three servers (DHCP, TFTP and NFS) as well as some modifications to the kernel and the ramdisk of the linux system that has to be booted via network.
I slightly modified the initial ramdisk to boot DSL just using DHCP and TFTP and thus significantly reduce the amount of configuration needed...
Setting up a boot server now is done in less than five minutes!