When ping size matters

Over the couple of days I’ve been fighting with sluggish internet performance from my office. The first thing I do, is the same as you, I start pinging. There is 0% packet loss and latency is a steady 10 ms. So where is the sluggishness coming from? I test the whole network stack from top to bottom and then back up again, router, vpn, switch, virtual network … everything checks out at 0% packet loss. Why are things so slow when ping is showing they should be fine?

I only figured it out when I started to play around with packet size. As I started increasing it, packet loss showed up

  • 10 bytes ~ 0% packet loss
  • 100 bytes ~ 5% packet loss
  • 1000 bytes ~ 30% packet loss
  • 10000 bytes ~ 80% packet loss

Now it made sense, I wasn’t seeing the packet loss because little packets sneak in on time. It was only when I start doing real work with large packets that the slow down occurs

Looking back, sometimes it’s best to keep things simple. I got side tracked because I initially blamed a weird hypervisor NIC driver glitch, that I was fighting with a couple years ago, but this time it was a “good” old ISP issue.