Architecture

There are 2 modes of Layer 1 capture

Mode 1) Layer 1 Trace

The Layer 1 Tracer (highlighted in Green) sits in parallel to the the main capture system this is shown below.

This mode allows full traditional PCAP (Layer2) based packet capture, with a addition of a small Layer 1 Trace buffer that can capture small fragments of corrupted or undefined layer 1 traffic.

Mode 2) Layer 1 Packet in Packet

In Layer 1 Packet in packet mode, the full layer 1 traffic is captured and written directly on disk as packet. For example in 10G mode packets 64 cycles of XGMII Control and Data into a single 640B packet that gets written to disk.

Layer 1 Packet in Packet requires an FPGA bitstream change, that can be done using

fmadiocli "config system fpga mode capture-4x10G-l1"

The raw data is packed into a packet as as shown below

What is shown above is how the the XGMII Control (Green) and XGMII Data (Blue) gets packed into a single packet.

Data is then visible using wireshark per below. The hilighted section clearly shows the full lazyer1 capture trace, including all idles, preamble, SOF/EOF