[Rdma-developers] Re: [openib-general] OpenIB and OpenRDMA: Convergence on common RDMA APIs and ULPs for Linux

[Grant Grundler]

On Fri, May 27, 2005 at 09:45:06AM -0700, Caitlin Bestler wrote:
> I'd like to add that RNIC-PI is planning on explicitly defining some of
> these "obvious" dependencies 
> between the RDMA stack and the primary IP stack. For example, the RDMA
> stack cannot maintain
> any connection in a state that contradicts current IP stack routing. It
> has to adapt or break the connection.

That's what I was just thinking. Could RNIC driver support both
existing linux NIC interfaces (e.g. use ifconfig/ethtool) *and*
openib RDMA interface?

Essentially that's what openib.org does today but uses ib_ipoib
driver to support TCP/IP communication.

Ie use an AF_INET socket to setup an RDMA connection like
the rdma_lat.c does:
	https://openib.org/svn/gen2/trunk/src/userspace/perftest/

Of course, I'm "blissfully ignorant" of how ugly that might be
in real world implementation of RNIC driver. Seems simple in
concept at least.

> We can't have an RNIC that has its own ARP table that is not in sync
> with the host's ARP table.

Yes, the RDMA and NIC parts of the driver would have to be aware
of each other.

grant

> An iWarp RDMA stack gains the benefit of many pre-existing network
> services (such as DNS, ARP
> and routing). But that also carries with it the need to not contradict
> those exisiting services. So it is
> both a benefit and a restriction -- and a major divergence from an IB
> RDMA stack.