In reply to Pierre-Louis Gingembre.

Hi Pierre-Louis,

That's an excellent question, and I'm glad you've given me the opportunity to clarify here.

The best way to think of the interconnections between the leafs through the spine is that it's similar to a port channel between typical FC switches. That is, we load-balance using SRC/DST/OXID.

The way Cisco handles ISLs in a port-channel is by using SRC/DST/OXID. Exchanges (which are made up of sequences, which are made up of FC frames) are sent across available links according to their OXID, not just their source and destination. Dynamic FCoE works exactly the same way. Just like if you lose a link inside of a port-channel you don't lose the entire connection, Dynamic FCoE creates the same behavior.

I'll be writing a deeper-dive on this soon, I promise.