[Bloat] Measuring latency-under-load consistently

[Jonathan Morton]

On 13 Mar, 2011, at 8:54 am, Fred Baker wrote:

>>> At the risk of sounding like someone mentioning a product, let me mention a product. This assumes, of course, that you're using Cisco equipment. But it allows you to measure delay (how long does it take to get from here to there), jitter (first derivative of delay/dt), and packet loss.
>> 
>> Ping does most of this, and is available on your actual computer.  A little post-processing of the output gives you jitter, if it doesn't supply that natively.
>> 
>> The point is, the existing tools don't typically measure latency *under load*.
> 
> Actually, SAA uses ping, and is intended precisely to do it under load. Ping is part of the existing traffic, and measures the RTT as experienced by traffic following the same path that the ping does.
> 
> Not sure exactly where you're going with that...

While you, and I, and other professional researchers and administrators are quite capable of generating a consistent, relevant load and then measuring around it...  we're the exceptional people.  Most people don't know jitter from a hole in the ground, they just know that Skype doesn't work.

The tool I'm working on does it in an integrated fashion, so the potential for user errors (or plain old marketing BS) creeping into the measurement is reduced.  That is, it generates the load and measures the effect on latency in one step.  The ability to measure some interesting things about the bulk flows at the same time is icing on the cake.

I do have consumer-grade connections in mind for this, though no doubt it will also be useful on professional-grade networks - especially wireless ones.  The consumer space is where the worst problems are currently visible.

 - Jonathan