[openib-general] IB Address Translation service

[Hal Rosenstock]

On Sat, 2005-03-05 at 10:22, David M. Brean wrote:
> There is an I-D for DHCP on IB.  IPoIB defines a "broadcast" address and 
> DHCP (and ARP) on IB use it.  Could make RARP work using this mechanism, 
> but as someone else pointed out, the IB hardware address contains a 
> QPN.  The I-D for IPoIB says something like:
> 
>     The link-layer address for IPoIB includes the QPN which might not be
>     constant across reboots or even across network interface resets.
>     Cached QPN entries, such as in static ARP entries or in RARP servers
>     will only work if the implementation(s) using these options ensure
>     that the QPN associated with an interface is invariant across
>     reboots/network resets.

That may be the requirement but I think there are some issues with
keeping the QPN invariant. Quoting Dror Goldenberg
(http://openib.org/pipermail/openib-general/2004-November/006765.html):
"Assigning specific QPN for ipoib requires allocation of QPN space which
is beyond IB spec verbs. Current verbs do not allow it. I don't have any
objection for that, except that you have to hold a set of preallocated
QPs with specific numbers and hand them over to privileged consumer when
requested to.  I wouldn't commit that it will work on any HCA
architecture."

-- Hal


> 
> So, there are requirements on the IPoIB implementation to make RARP 
> work.  Folks in the IPoIB work group decided not to go much further than 
> these statements for RARP support since most folks felt that DHCP is (de 
> facto) replacement.
> 
> -David
> 
> 
> >-- greg
> >
> >
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