Availability of MPI over inet2 protocol

Donald Becker becker at scyld.com
Sun Dec 1 06:12:40 PST 2002

On 1 Dec 2002, Patrick Geoffray wrote:

> On Sun, 2002-12-01 at 04:53, Kragen Sitaker wrote:
> > Don Becker writes:
> > > Improve in what way?  IPv6 is slower and more complex.
> > 
> > IIRC, the designers of IPv6 left out the parts of IPv4 that tended to
> > bottleneck routers, like recalculating header checksums after
> > decrementing the TTL; they intended to make IPv6 faster than IPv4 on
> > the same amount of hardware.  I guess you think they failed?

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 allocations of the address space to
simplify routing.

> Do you think it will make a bit of a difference at the MPI level ?
> There are some characteristics of long distance networking that you will
> never change, like the speed of light. IPv4 or IPv6, don't expect good
> performance running MPI codes across the Internet, unless there is no
> communication. 
> When the Grid Computing community will finally realize that... :-)

It amazes me when I give a talk and am pounded with hostile questions
about communication latency, bisection bandwidth, parallel file I/O,
the impossibility of converting a specific algorithm, and application
availability.  The same audience, just a few minutes later, nods in
agreements with grid computing, cycle scavenging and "peer-to-peer"
(sic) computing claiming to be able to do the same applications.

Donald Becker				becker at scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Scyld Beowulf cluster system
Annapolis MD 21403			410-990-9993

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