A New Sublayer


The multi-lane architecture within 100G Ethernet that comprises the PCS Lanes, CAUI and Gearbox (depending on CFP) represent a whole new sublayer of the network that must be specifically tested.

This new sublayer exists only between two directly adjacent network elements that are connected via the CFP interfaces.

To support this there are a number of new error and alarm conditions that must be monitored. These include error and alarm conditions that can be detected in multiple lanes at the same time.

For example now that there are multiple WDM channels being used it is possible to detect physical layer conditions such as Loss Of Signal (LOS) on any of the 4 optical channels in a 4 x 25G system or any of the 10 channels in a 10 x 10G system.

At the PCS level there are several conditions that can be detected including invalid alignment markers and loss of block that may occur in any of the 20 PCS lanes. It is important that these conditions are monitored and reported across all lanes.

It must be understood that failure or any conditions at the PCS/CAUI/Physical layer will result in complete loss of the Ethernet link. Although only a single PCS lane or optical channel may suffer disruption these will prevent the recombination of the serial data stream at the receiving device. In this case the Ethernet link will fail completely and no Ethernet frames will be received at the device. It is therefore imperative that this layer operates without any error and must be tested to ensure this is the case.