[RRG] Possible Identifier Properties

[RJ Atkinson <rja@extremenetworks.com>]

Earlier, Lixia Zhang wrote:
% BTW here is what I got from other msgs on this thread,
% that is MAC address is not an ideal node ID in the
% strict sense, as it is associated with a specific
% interface, while hosts are increasingly multihomed
% today.

I would suggest that we distinguish carefully between:

A) using a MAC address as an interface-ID [MAC]
A) using a MAC address as a node-ID [MAC]
B) using a MAC address as a handy set of bits
   to use in deriving a node-ID.  [f(MAC)]

% There are really two issues:
% 1/ the need for a unique node ID

Depending on the details of one's design, I do not
think that one necessarily needs a Node-ID to be
absolutely globally-unique.

I do think that it is normally helpful if a Node-ID
is very likely to be unique.

Again, depending on the details of one's design,
I also think it is necessary for a Node-ID to be
unique within the context of some given Locator.

% 2/ an engineering judgment call of whether
%    one could borrow MAC address to serve the
%    above purpose.
%
% 2/ represents an engineering tradeoff
%    because the borrowing saves the trouble
%    of managing another new ID space.

If there were a new identifier space that in no way
derived from any property of the node, this would
create some significant issues:
	- political (e.g. who manages that space ?
                     and under what rules ?)
	- deployment (e.g. getting IDs into systems)
	- other

So I think a very reasonable approach is to use
some MAC that belongs to a node as input to some
function that then generates a Node Identifier.
One could use such a generated Node Identifier
to name the node -- rather than limiting that
Identifier to naming a single interface of the node.

As it happens, IPv6 normally does something pretty
reasonable here, which is to use the MAC address
bits and apply a function to transform them into
an EUI-64.  While current IPv6 uses a different
EUI-64 on each different interface, one could easily
imagine an alternate design where a common EUI-64
were used to name the node (hence a common EUI-64
is used with ALL interfaces).

Cheers,

Ran Atkinson
rja@extremenetworks.com



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