[openib-general] RFC: SDP plans

[Bryan O'Sullivan]

On Mon, 2006-02-27 at 21:33 +0200, Michael S. Tsirkin wrote:

> So its possible to make the protocol family configurable in userspace sdp
> library (libsdp) and then include libsdp in Release 1.0 and it will work with
> whatever SDP code makes it upstream.

The one thing that worries me about this is that it appears that libsdp
silently falls back to using TCP at the moment, at least based on some
internal tests we did with the environment slightly and inadvertantly
misconfigured.

If this is the case, then having the protocol family potentially change
out under SDP could make it occur that a kernel update (or a switch to a
kernel that doesn't have SDP available) would cause apps to silently
start using IPoIB instead of SDP.  Which is the sort of behaviour that
leads to rapid hair loss on the part of both users and support people.

If libsdp were to abort by default if SDP wasn't available, then I think
we'd have a fairly strong case that we're not creating a nightmare for
ourselves.

	<b