[ofw] RE: [RFC] Remove path query from IPoIB

[Hal Rosenstock]

On Mon, Aug 11, 2008 at 2:39 PM, Fab Tillier
<ftillier at windows.microsoft.com> wrote:
>>> Not that I'm aware of, but there's nothing in the spec that says the
>>> GRH should not be sent.
>>
>> I was thinking that this was simply a matter of inefficiency, but it
>> may an interoperability problem.  If a different implementation of
>> IPoIB doesn't send the GRH, it sounds like there's an issue here.  I
>> don't believe that the linux implementation sends a GRH with unicast
>> packets unless the packet crosses an IB subnet.
>
> Packets from Linux to Windows will be IP, so will do the address resolution and the endpoint will be created based on those packets, with the GRH.  Further unicast traffic without a GRH would be fine.

Does Windows require the GRH (for some part of IPoIB) ? If so, that
would cause an interop issue with implementations which don't send GRH
(like Linux).

-- Hal

> What you end up with dropping packets that are received without a GRH for which there isn't an existing endpoint ends.  I would suspect the Linux IPoIB does the same, though maybe it doesn't.
>
> -Fab
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