Originally Posted by Stern
... the RIM infrastructure has it's own layers much like the components on the bes.
Communication (or traffic) from one layer to its next adjacent (vertical) layer is called a "protocol." e.g. link-layer to network-layer. Communication (or traffic) by one layer on one stack to its corresponding layer on another (device) stack (horizontal) is called an "interface." e.g. device to tower air interface (CDMA).
A word-picture gets complicated and is beyond my authoring skills. And, as I mentioned, I cannot re-locate the carrier-blackberry protocol-interface model graphic that positions all this in one graphic (albeit a busy graphic).