[openib-general] [RFC] IB address translation using ARP

[Caitlin Bestler]

On 10 Oct 2005 10:45:59 -0400, Hal Rosenstock <halr at voltaire.com> wrote:
>
> On Sun, 2005-10-09 at 10:19, Sean Hefty wrote:
> > >I think iWARP can be on top of TCP or SCTP. But why wouldn't it care ?
> >
> > I'm referring to the case that iWarp is running over TCP. I know that it
> can
> > run over SCTP, but I'm not familiar with the details of that protocol.
> With
> > TCP, this is an end-to-end connection, so layering iWarp over it, only
> the
> > endpoints need to deal with it. I believe the same is true for SCTP.
>
> Yes, SCTP is similar in those regards.
>
> > >Doesn't a routing decision still need to be made at the IP layer ?
> >
> > Routing of the IP packets is done at the IP layer, but I don't see how
> this
> > affects iWarp.
>
> It does under the "covers", those covers being IP routing.
>
> > >Doesn't the IP next hop need to be determined (e.g. gateway when the
> > >destination is off the local IP subnet) ? Is there something that
> > >precludes iWARP from working across IP subnets ?
> >
> > I can't think of anything that would preclude iWarp from working
> > across subnets.
>
> Doesn't the IP next hop need determining in that case ? Why is that not
> relevant ? I don't think the iWARP connection is end to end in all
> cases.



Of course it's end to end. It's just that only the end points understand
that it is an iWARP connection.

Or more properly, the underlying transport (or "LLP") connections
are end to end, but the iWARP semantics exist only in the RDMA
endpoints.

That is why iWARP works across multiple subnets. We've actually
done true worldwide connections. The exisitng IP network carries
the iWARP traffic because it is indeed just TCP traffic to the
intermediate network.
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