[openib-general] basic IB doubt

[Caitlin Bestler]

Woodruff, Robert J wrote:
> Catlin wrote,
> 
>> For iWARP there are network performance reasons why in-order memory
>> writes will never be guaranteed.
> 
> For iWarp, or any other RDMA over Ethernet protocol, the
> behavior is not to guarantee all packets are written
> in-order, just that the last byte of the last packet is
> written last. This can easily be implemented in an iWarp card
> or by the driver with minimal performance impact in most cases.
> 
> So for example, if the last packet arrives before all the
> other packets have arrived, the iWarp card or driver does not
> place that data of the last packet until all the other
> packets have arrived.
> 
> woody

Another point, even if a vendor were to implement the firmware
you suggest, how does the Data Source know that it is safe to
use just RDMA Writes? The enabling firmware is in the Data Sink.

Applications certainly do not want to have to validate the model
of the RNIC that they are connected with.