Sounds like Sun's ND (Network Disk) protocol, from before NFS was usable for the root partition...Following up my own post -- see ndbootd(8). You need the client, too, but it might be a good reference.
It's for SUN PROM netbooting, not a general solution used to be. I'm familar with Sun ND and other (intermediate) block level solutions in pre-NFS (rootfs capable or not) age like what SONY NEWS and/or CASIO (yes, they made UNIX WS at that time). Z-SAN is far beyond them and I need iSCSI like functionalities and beyonds. It's worth pursuing DataPlow to disclose (or port) their own filesy product named SFS (what's the relationship with SVR4 sfs?) to NetBSD, however, it'd just be a pipe-dreaming, so just want to practise FFS on it for this time. Toru Nishimura / ALKYL Technology