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From: Bogdan Costescu (Bogdan.Costescu_at_[hidden])
Date: 2006-04-04 05:16:41

On Mon, 3 Apr 2006, Christian Kauhaus wrote:

> 1. Put IPv[46] addresses into the machinefile. Since they are
> protocol-specific, both rsh/ssh uses them just the way they are.

Yes, this would work. The machinefile could come from the user or from
a batch/queueing system, but this should signify that the producer
knows about the configuration of the machines and wants these specific
addresses to be used.

> 2. Put hostnames into the machinefile. Both rsh/ssh and OpenMPI perform
> their own resolver lookup.

>From what I understand, OpenMPI wants to have its daemons running on
the machines and then the interface configuration and communication
channel establishment follows, so the 2 phases are not connected to
each other.

The question is then what to do about the names given in the
machinefile ? Should they just be passed to the rsh/ssh client hoping
that they would work ? Should there be an option for resolving the
names to a user (or maybe admin) specific version of IP which should
then be passed to rsh/ssh ? Or should there be a list of IP addresses
that are tried in sequence ? Hmm, maybe all of the above, with some
means to choose between them ?

> Your setup (IPv6 addresses given by the resolver, but no IPv6-aware ssh)
> could be handled in both ways: either by putting numeric IPv4-addresses
> into the machinefile, or by specifying 'ssh -4'.

Yes. Please keep in mind however that the opposite situation might
also occur (starting via IPv6, MPI communication via IPv4).

Bogdan Costescu
IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu_at_[hidden]