db@helium.East.Sun.COM (David Brownell) (08/29/89)
In article <8908161254.AA03742@vax.ftp.com> dab@VAX.FTP.COM writes: > It seems that BOOTP would have made a better base to do dynamic > address assignment from than RARP. Why the choice? > > David Bridgham Well, neither RFC 903 (for RARP) nor RFC 951 (BOOTP) describe dynamic address assignment. No other RFC does, either. This meant either a new protocol, or an extension to an existing one. The RARP implementation we provide remains compliant with RFC 903. There are two key arguments I can give you as to why we extended RARP, rather than extending BOOTP or defining yet another protocol. It's interesting that historically we proposed a new protocol, and went back to modifying an existing one for reasons of compatibility: (1) We were already using RARP. There's a large installed base of PROMS complying to RFC 906 (RARP/TFTP) for diskless booting, and we needed solutions that wouldn't exclude those systems. (2) RARP is actually a better base than BOOTP. It's performing operations at the link/network level boundary using a protocol that runs at those levels. RARP servers can often access and manipulate information that's hidden by an IP-level interface. (1) is practical, (2) verges on religious. You also have to ask whether you're solving the dynamic address assignment problem, or the "how does a host configure itself" problem; it seems to me that BOOTP handles the latter better than the former. The more information you're trying to pack into that "configure yourself this way" response, the more you need an extensible monolithic protocol. Given (1) there wasn't a lot of need to discuss (2) outside of a debate on what Internet standards should get created to do dynamic address assignment and (separately) what standards should get created to allow automatic system installation. I can't comment authoritatively on those two standards issues since I'm not engaged in the discussions any more, and haven't actually gotten an update in a while. David Brownell db@east.sun.com Sun Desktop Systems Software sun!suneast!db Billerica, MA David Brownell db@east.sun.com Sun Entry Systems Software sun!suneast!db Billerica, MA