IEEE 802.3 40GBase-KR4
The IEEE 40GBase-KR4 interface is an interface for backplane Ethernet that will meet the increasing bandwidth requirements in the I/O area of blade servers and establish 40 Gigabit Ethernet in server backplanes. It is a 40- gigabit interface for point-to-point connectivity across backplane PCB traces.
The interface uses the Physical Coding Sublayer( PCS) and the Physical Media Attachment( PMA) and a sublayer for autonegotiation. Autonegotiation allows the highest possible data rate to be selected between the other interfaces1000Base-KX, 10GBase-KR and 10GBase-KX4.
40GBase-KR4 corresponds as far as possible to the 10GBase-KR interface specified by the IEEE 802.3ap working group. The bridgeable distance is one meter, the connection is made over four lanes via the copper backplane with a data rate of 10.3125 GBaud. 40GBase-KR4 has 64B66B coding and differential output levels between 800 mV and 1.2 V.
Backplane Ethernet is particularly interesting for blade servers and backplane connections in other systems.