boot script for install NetBSD

[z-80a]

NiKiZe, thanks for the examples, but i don't quite understand how to pass filenames through the script IPXE, because in this case, in the configuration DHCP they are not.
In fact, according to the man NetBSD, the decision to transfer the filenames to the client for download is made at the stage of exchange of DHCP packets based on the substring "NetBSD:i386:libsa" and vendor class ID.
Is it possible to pass them through a script?
p.s. Sorry by very bed english