The ability to auto-negotiate SFP+ Passive DAC

While data center administrators have a number of 10GE interfaces to choose from, including 10GBASE-CX4, SFP+ Fiber, SFP+ Passive DAC, and 10GBASE-T, it is the current generation of 10GBASE-T technology that is driving mass adoption of 10GE. This multi-part article analyzes the key differences between 10GBASE-T and other 10GE physical layer technologies, and the impact of 10GBASE-T’s availability as a LAN-on-Motherboard (LOM) solution on the Romley generation of servers. According to Crehan Research, 10GBASE-T, the fastest growing 10GE connectivity solution in data centers, is expected to exceed all other 10GE alternatives by 2015 and reach more than 30 million ports in 2016.  Small Form-factor Pluggable (SFP+) passive assemblies use less power and have smaller cables than 10GBASE-CX4. As a result, SFP+ DAC cable deployments have been growing in usage over the past few years.However, they have a limited distance (typically up to 5m for passive solutions and up to 7m for the more expensive and higher power active modules), commonly cannot operate between equipment vendors, and are not as flexible or cost effective as an open 10GBASE-T system.Another key benefit of 10GBASE-T is backward compatibility. Using the standard RJ45 connector, 10GBASE-T ports can connect to 1 Gigabit and even 100 Megabit interfaces, allowing end-users to transparently upgrade to 10GE from their Fast Ethernet/Gigabit Ethernet networks. The ability to auto-negotiate between 1G and 10G speeds allows users to determine which links will be high speed and low speed, and switch between the two without a hardware upgrade. In comparison, 10GBASE-SFP+ Passive DAC products typically have limited or no backward compatibility with previous speeds.