Valkyrie Knowledge Base

Port Capture

This page describes the ValkyrieManager Capture panel. The panel allows you to configure the capture settings for the currently selected port and to inspect the result of the capture.

Overview

All packets arriving at a port are counted and analyzed if they contain test payloads. In addition, selected packets can be retained (captured) for closer inspection using the capture mechanism.

capture.png

Configuration


Start Trigger 

The Start Trigger control when the capture function actually begins to collect packets in the capture buffer. The default behavior is to begin collection when capture is started (aka. the From ON option). Other options include:

  • From FCS Error: Begin collection when the first FCS error in a received packet is detected.
  • From Filter: Begin collection when the first packet that matches the specified filter is received.
  • From Payload Error: Begin collection when the first payload error in a received packet is detected.

Stop Trigger 

The Stop Trigger can be used to control when the capture function stops collecting packets. When using a start trigger, capturing is automatically stopped if the internal capture buffer runs full. When using only a stop trigger, the hardware capture buffer retains as many packets as possible up until the stop trigger event.

The Stop Trigger options are identical to the Start Trigger options.

However for ports on 10G and 1 G modules, you can select “Stop trigger” “Until User Stop”. This will cause the system to capture circularly, so you always have the last packets received in your capture buffer. I.e.  you start capture, run traffic until it stops, and then you manually stop the capture.

Packets To Keep

This option control what type of packets to keep. This may help you make the most of the limited capture buffer.

How Much To Keep

This option how much of the captured packets to keep. Using this option will increase the number of packets you can keep in the internal capture buffer. The ValkyrieManager will always report the total length of the packet even if it has been truncated due to this option.

Starting Capture

You can manually start capture on a port by pressing the Start Capture button at the top of the panel. If the checkbox next to the button is checked the Global Statistics Start Traffic button will also start capture of the ports in your testbed.

Capture Results

The captured packets will be uploaded from the chassis while capture is ongoing. You can thus inspect them both when the capture is still in progress and when the capture operation has completed.

Results Grid

Each captured packet will be displayed as a row in the Result Grid. The following values are reported for each packet:

  • Timestamp: The timestamp for when the packet was received relative to capture start.
  • Latency: The latency value calculated from the Xena test payload data (not valid for other types of packets)
  • IFG: The Inter-Frame Gap compared to the previous packet.
  • Source: The SMAC address from the packet.
  • Destination: The DMAC address from the packet.
  • Protocol: A summary of the decoded packet headers in the packet.
  • Full Length: The original length of the captured packet before any optional truncation due to the How Much To Keep option has been performed.
  • Captured Length: The actual length of the captured packet after optional truncation.

If you select a packet in the grid a Wireshark-like packet header view will be displayed below the grid where the packet content can be inspected.

Capture Graph

The ValkyrieManager also provides a graphical histogram view of the length or spacing of the captured packets, as well as the latencies.

Saving or Exporting Capture Data

By using the Save Packets button you can save the captured packets to a PCAP or a PCAP-NG (PCAP Next Generation) file.

You can also launch Wireshark directly with the captured packets as an argument by pressing the Launch Wireshark button. This obviously requires that Wireshark has been installed on your PC.

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