Access Gateway – Brocade
NPV (N_port Virtualization (not NPIV) – Cisco
Transparent Mode – QLogic
These are all names for the basic idea / functionality but as there’s no standard the vendors have made up their own names for it.
A switch in Access Gateway (AG) mode does not consume Domain IDs, you can do port mapping, needs NPIV on the port in the switch that it connects to. AG requires a switch / fabric to connect to as it doesn’t run the normal fibre channel services.
It is very useful in case you are going to mix vendors in your fabric. Meaning you can populate the core with Brocade switches and then connect other vendors’ switches in the above modes to the Brocade switches.
On some QLogic switches you can also set a port into TR-mode, see this post on HP’s EBC forum about how to do it. It is not exactly the same as AG or NPV, because you still need to do zoning on the QLogic switch.
There is also the IPM by Qlogic for IBM – it looks like a module that you cannot switch between ‘fabric’ and ‘IPM’ mode. Which is what you can do on a Cisco or on a Brocade switch.