Ethernet switches and AVB

I'm building a new home studio network and plan to leverage ethernet (and MOTU's AVB and rtpMIDI protocols) for audio and MIDI interconnections between different racks of gear. Two quick questions:

* Is MOTU's AVB switch the only readily available switch that supports AVB and all of the related IEEE protocols, or are their other options?

* MOTU's switch documentation notes that AVB can be "turned off" on a port if desired...Not sure why anyone would specifically want to do that. Can someone explain why?