David,

So all of you userland control-plane fanatics, how will you handle
things like NFS root with these daemon-required variants of NDISC and
ARP?

   Do it in the initial ramdisk, we only need the daemon to setup the
 NDISC entries to talk to the NFS server. :-)

   There is obviously a cost associated with this, a deployment cost.
 But there are additional factors we must consider. In a later e-mail
 you state that Linux is a generic purpose operating system; how many
 users need to boot from a NFS root (besides myself :-)? I think that we
 must take into consideration that currently Linux is used in lots of
 distinct environments, not only Desktop computers, and servers, but
 also smaller devices. Configuration/Flexibility vs. optimization is
 something that varies a lot depending on the deployment you are talking
 about, and in most of my scenarios, a small mobile device isn't
 required at the moment to push 100Mbps (optimization) but must be
 capable of verifying it's peers and maintaining secure connections
 (flexibility). So, let's be generic?

   I might have some cycles during the month to code up something in
 this direction, at least for an initial review, i'll try to do so.

   Also, the reliability of a system depends on a lot of things, but
 please, let's not use the assumption that because everything sits in
 the kernel, it will be stable as the number of 'points of failure' is
 smaller; this is only true as long as people work to have stable
 components -- and this is independent of where the components sit. A
 few kernel versions ago (2.6.8 if i remember correctly) i couldn't even
 remove a used network interface safely from the system without hanging
 the network stack. It is possible to have stable user-space code, if
 people developing it work to and make sure it is stable.

   Hugo