Availability of MPI over inet2 protocol

Eugen Leitl eugen at leitl.org
Sun Dec 1 07:42:52 PST 2002

On Sun, 1 Dec 2002, Donald Becker wrote:

> One simplication for routers, compared against the significantly
> larger and more complex header.  The routers now have many more
> decisions to make based on the address.  There were hand-waving
> arguments that larger addresses would somehow make geographical
> addressing possible, and that there would somehow be rational

True geographic addressing would work with say, labelling the nodes with
polar coordinates. 128 bit would be more than sufficient for that (even
the NIC raw MAC address space allows for roughly 1 node/m^2 of Earth
surface). But I understand one can't just pick up a large IPv6 address
subspace and run with it, to say use it for labeling nodes in an ad hoc
wireless network.

> allocations of the address space to simplify routing.

Assuming node ID being derived from, say, WGS 84 in a straightforward
notion (latitude|longitude|height) and the network connectivity would not
create obstructions to packets (either following a regular mesh, or being
a high-dimensional grid) then only a few parallelizable vector lookups (of
the 'this link goes to the node closest to target address, so stream
packet there') are sufficient for a routing decision. This could be easily
accomplished at relativistic speeds, while the header packets are
streaming by. Given that at 10 GBps a bit is just <3 cm long a short coil
of fiber after the beam splitter would do as a shallow FIFO so it could be
done purely photonically.

In case of using NIC MACs only trivial modification to switch ASICs would
be necessary to allow them to handle true meshes instead of just trees
(and limited by the MAC lookup size, too).

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