Building an Inexpensive Performance Packet Generator

You know that nice feeling you get when someone surprises you with a feature you weren’t expecting, but that totally change the way you use something. Like when your son told you about that free HBO app so you can now watch HBO on your iPad.” Well, recently Solarflare released an update to SolarCapture Pro (SCP V1.3) with just such a feature, replay.

On the surface replay sounds rather hum drum, you can replay libpcap files out to an Ethernet interface. So for the Uber nerds out there yes, you can plug this into Ostenato and make a poor man’s high-performance Ixia on the cheap under $2,250 (you’ll need an SFN7122F & the software SFS-SCP) plus the cost of your server.

If one considers that Solarflare provides the highest performance network adapters currently available for both 10GbE & 40GbE.  This replay feature could be extremely powerful. For example, someone could load a server up with memory, spin up one or more very large libpcap files then use the following command to blast them into their network at wire-rate.

solar_replay pps=1.5e6 prebuffer repeat=512 eth2=play1.pcap eth3=play1.pcap

In this example replay will sustain 1.5 million packets per second (Mpps), note this rate can be as high as 14.8Mpps if your pcap file is all small packets. Next before the replay actually starts play1.pcap will be “prebuffered” meaning that it will be loaded into memory before the replay begins so that disk performance won’t be a factor in the playback. Next, the replay will loop 512 times.  Finally, it will replay the same buffer out both 10GbE or 40GbE ports on the adapter, eth2 & eth3.

So what will this look like? Simple a storm of packets on two interfaces that are hopefully attached to different switches in your infrastructure. Note that the packet rate is actually limited by the size of the packets.

Additionally, you can pin the replay to specific cores, increase the number of buffers, adjust port & time ranges of what you want to replay from the pcap files, and throttle the rate to a multiple of the initial capture speed.

This is by far the most advanced replay capability available today on an ASIC based network adapter. SolarCapture is extremely powerful, and this sample just scratches the surface of what it is capable of.

If you’re interested in taking SolarCapture out for a test drive, or just want to learn more feel free to contact me, or reach out directly to Solarflare.

Leave a Reply