---
title: "Architecture"
slug: "features-layer1-capture-architecture"
updated: 2025-03-30T05:49:08Z
published: 2025-03-30T05:49:08Z
canonical: "docs.fmad.io/features-layer1-capture-architecture"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fmad.io/llms.txt
> Use this file to discover all available pages before exploring further.

# 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.

![](https://cdn.document360.io/b9aab0c4-36d0-4616-9673-30b661455571/Images/Documentation/image(159).png?sv=2026-02-06&spr=https&st=2026-11-13T20%3A44%3A39Z&se=2026-11-13T21%3A44%3A39Z&sr=c&sp=r&sig=eReUdxbGit7E8pD8%2BoCl9pf4C7efQ5IorON%2Bsopdkb0%3D)

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

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

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

![](https://cdn.document360.io/b9aab0c4-36d0-4616-9673-30b661455571/Images/Documentation/L1 PacketInPacket.drawio (2).png?sv=2026-02-06&spr=https&st=2026-11-13T20%3A44%3A39Z&se=2026-11-13T21%3A44%3A39Z&sr=c&sp=r&sig=eReUdxbGit7E8pD8%2BoCl9pf4C7efQ5IorON%2Bsopdkb0%3D)

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

![](https://cdn.document360.io/b9aab0c4-36d0-4616-9673-30b661455571/Images/Documentation/image(160).png?sv=2026-02-06&spr=https&st=2026-11-13T20%3A44%3A39Z&se=2026-11-13T21%3A44%3A39Z&sr=c&sp=r&sig=eReUdxbGit7E8pD8%2BoCl9pf4C7efQ5IorON%2Bsopdkb0%3D)