We have been moving away from IB for our platform (algorithmic trading) since Ethernet now has almost comparable latency and is a lot easier to understand and manage.
IB is actually easier to reason about and debug than DCE, but obviously a different community of practice.
But I think this is the way the market is going in the longer term.
What I'm getting at is setting up clusters larger than what you can fit behind a single switch. So you'll want e.g. a CLOS fabric with multipathing (the typical IB setup, FWIW). As Trill and SPB seem pretty dead, it seems the momentum is to do the multipathing at the L3 level, using the aforementioned EPVN+VXLAN+BGP, or something similar.
Or maybe you could do one "provisioning and admin" VLAN that spans the entire cluster and which uses spanning tree, and then the high-performance RDMA stuff uses the per-leaf VLAN's and L3 multipath routing? Is that simpler and better performing that EVPN + VXLAN?
What is the routing latency on such BGP setups BTW? I find it hard to image you can get even close to eth (not to mention IB!) L2 latencies? Or can the fast paths be done in hw (or FPGA's)?
In most ASICs everything is the same latency since packets go through the whole pipeline whether they use all the functionality or not. Anyway, the latency of plain routing would have to be equal or faster than VXLAN encap + routing.
Their ethernet accelerator VMA stands for "Voltaire Messaging Accelerator".