In one word, NOTHING. They are all three letter acronyms used to describe the same thing. All three of these acronyms describe an architectural collection of Ethernet extensions (based on open standards) designed to improve Ethernet networking and management in the Data Center. The Ethernet extensions are as follows:- Priority-Based Flow Control = P802.1Qbb- Enhanced Transmission Selection = P802.1Qaz- Congestion Notification = P802.1Qau- Data Center Bridging Exchange Protocol = This protocol is expected to leverage functionality provided by 802.1AB (LLDP)Cisco has co-authored many of the standards referenced above and is focused on providing a standards-based solution for a Unified Fabric in the data center The IEEE has decided to use the term “DCB” (Data Center Bridging) to describe these extensions to the industry. You can find additional information here:http://www.ieee802.org/1/pages/dcbridges.html In summary, all three acronyms mean essentially the same thing “today”. Cisco’s DCE products and solutions are NOT proprietary and are based on open standards.