Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!think!ames!pasteur!ucbvax!PESCADERO.STANFORD.EDU!deering
From: deering@PESCADERO.STANFORD.EDU (Steve Deering)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: BOOTP Extensions
Message-ID: <88.10.08.1713.750@pescadero.stanford.edu>
Date: 9 Oct 88 00:13:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 27


	From <mar@ATHENA.MIT.EDU>:
	...We are designing a new protocol for complete on-the-fly generation
	of new addresses along with assignment of netmask, broadcast address,
	and default gateway. ...

In general, a single default gateway address is insufficient (assuming
there is more than one gateway on the subnet), because that single gateway
may fail, leaving the host unable to communicate off-subnet despite the
presence of other operational gateways.  The draft Host Requirements RFC
recommends that a host be configured with a *set* of default gateway
addresses.  The Host Requirements working group is also working on a
proposal for dynamic discovery of all operational gateways on a single
subnet, using multicast or broadcast where available.

Regarding on-the-fly generation of host addresses, doesn't the small
size of IP addresses present a fundamental problem?  Many networks
are class C or subnetted class B, with only 8 bits of host number.
If the host population is large or very volatile, you will have to
recycle addresses, but in the absence of human administrative control,
there is no way to determine reliably that an address is free for
reassignment.  You can't just poll an address to see if it is in
use, because the user of the address may be temporarily unreachable
from the system that assigns the addresses.  Are you planning to
handle address recycling?

Steve