[Federated-fs] "root" discovery and other bootstrapping protocols.

[Ellard, Daniel]

One of the topics that was mentioned as extremely desireable (if not
required) during discussion at the IETF meeting in Philadelphia is the
"discovery" protocol for finding a root of the namespace (without
requiring substantial per-client/per-locale configuration).

We talked about this yesterday on the weekly conference call, and came
up with two divergent but complementary bootstrapping modes.  Both of
these require some client changes and config.

The two different modes can be characterized as "passive" and
"aggressive" (pithier names welcome):

Passive: "Wherever I go, there I am."  A client can find a root of the
local namespace with no a priori knowledge whatsoever.  This could be
done with something similar to a DHCP service, or a reserved DNS name or
SRV record.  For example, by convention, each DNS server will resolve a
name like "localfedfs" to the IP of a "local" server that exports a
namespace root at a known location.  If you use DHCP to find your DNS
server, you'll get a local root.  If you set your DNS servers by hand,
you'll also be choosing your root.

Aggressive: "I know where I want to be; take me there."  This uses an
AFS-like view of the world, where it is possible to symbolically name
namespace root servers.  For example, the client might have a special
directory (i.e., "/fedfs") that is initially empty.  If the client
attempts to cd in a subdirectory of this directory ("cd
/fedfs/netapp.com") the client will interpret the name of directory as
the name of the DNS name to ask for SRV records for namespace root
servers owned by netapp.com.  Subdomains would be implemented by more
specific name (i.e., "cd /fedfs/nane.netapp.com").  For systems that
support autofs, it's easy to imagine how this can be implemented as a
autofs module (although there's still an extra protocol to be defined
for this module).

According to my notes, Paul LeMahieu signed up to sketch out the
"passive" model and Craig Everhart is going to sketch out the
"aggressive" model (which he's mostly done in the form of the I-D that
he mailed out yesterday).  (I'm sure they'll correct any mistakes or
misrepresentations I've made.)

-Dan


-- 
Daniel Ellard, Ph.D.
NetApp Advanced Technology Group