[openib-general] IB Address Translation service

[Greg Lindahl]

On Fri, Mar 04, 2005 at 11:58:33AM -0800, Tom Duffy wrote:

> In any event, I think being able to plop an IB network in an Ethernet
> world will require things like RARP to work.  If there is no spec now,
> it should be written.

Much more important is understanding the role of RARP in the ethernet
world.

It is *not* something you do to find _someone else's_ IP addr from
their MAC addr. It's what you do to find your _own_ IP addr because
you're booting. Ethernet protocols such as IP include enough IP
information to talk back to someone who sent you a packet. So you
don't need to find out an IP addr from a MAC for remote nodes on a
regular basis. Instead, you find out a MAC addr from an IP address,
which is ARP.

RARP is little used now that DHCP is popular.

Now it would be nice for ethernet broadcast packets to just work(tm)
with IPoIB. "ping -b" is an example of a user-level program that
generates a broadcast packet.  DHCP clients also generate such
packets, and DHCP servers listen for them. Getting a RARP client and
server to work ought to be the same as a DHCP client and server.

-- greg