Roland Dreier <rdre...@cisco.com> wrote: > I agree that implementing DCB is important for IBoE, but why do you say > that a classical ethernet fabric with global pause isn't usable? That > should be roughly equivalent to an IB fabric that uses only a single VL, > which is the case for many production IB fabrics.
To start with, no matter how many data VLs are used (e.g one), all the crucial management traffic (SMPs) go on VL15 which is on the one hand lossy and on the other hand not subject to congestion when other VLs are. Now how would you manage your Cisco switch --remotely-- on a globally paused fabric when some multicast receiver hasn't had its breakfast and now slows the sender while filling the queues throughout the congestion tree where this switch is part of? To continue with, lossless is good, but to make your cluster usable under congestion, you need congestion control, that is QCN, which is designed/optimized to the case of multiple TCs. Also, IBoE can potentially find its way to much more complex environments than IB has, specifically, to clusters whose hosts are acting as hypervisors running many many VMs and the underlying fabrics does consolidates many types of traffic, globally pausing a port can dramatically reduce the efficiency of such computing center which probably was built originally to increase efficiency. I believe that the ixgbe team well understand that, and hence their continued DCB efforts can make the combination of RXE with Niantic/ixgbe very intresting to test. Or. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
