40GbE and 100GbE in Ethernet's Future

The IEEE 802.3 Higher Speed Study Group (HSSG) has decided that the next speed for Ethernet will be both 40GbE and 100GbE.

Originally the HHSG had planned on doing just 100GbE, but industry feedback changed the plans somewhat.

"The reason for the two rates is because the two areas of applications have different growth rates and wouldn't be properly services by one rate," John D'Ambrosia, chair of the Higher Speed Study Group, told internetnews.com.

"Earlier this year after the decision had been made to choose the 100GbE rate, individuals involved with the server industry pointed out that this rate didn't address the needs of their markets."

D'Ambrosia explained that servers are doubling in their bandwidth needs every 24 months while core networking bandwidth needs are doubling every 18 months.

The 40GbE rate is intended to address server and computing applications and the 100GbE rate is for aggregation and core networking applications.

For 40GbE, there will be specifications for at least three physical layers to support 40GbE operations, including at least 100 meters on OM3 multimode fiber; at least 10 meters over copper cable assembly; and at least 1 meter over backplane.

For 100GbE operations physical layer specifications will include 40 kilometers on single-mode fiber and at least 10 meters over copper assembly.

Though Ethernet is moving to both 40GbE and 100GbE, it won't be moving with two different standards.

"We're going to develop one amendment that will address both rates," D'Ambrosia said. "Whether it's a throttle down or if it's just the number of lanes, it will still be one specification that this project will develop into both speeds."

Among the issues that are likely to come up as the new standard emerges are concerns over power and heat, though D'Ambrosia is confident those concerns can be addressed.

The new IEEE specification will also need to find a way to work with existing Optical Transport Networking (OTM) particularly at 40Gbps (OC-768).

"OC-768 is defined and deployed, whereas 100 G is an area where the ITU is beginning to understand what we're doing and working with their own specifications to provide and ease of transition between Ethernet layers and optical transport layers," D'Ambrosia noted.