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In this context, jitter is a statement of deviation. In fact, engineers/techs who only work on tcp/ip networks will also use the word synonymous with "late packet arrival." I have never looked at what exactly the n% means but lower is better and I think 2% is probably ok.I saw something about it on Wikipedia, but It gives me a headache to think about it simply due to my objection to the word being used in this context at all. In all other areas of engineering it describes a deviation from a fixed expected rate. I would love to hear somebody tell me how a packet switching network has or ever claimed to have a fixed expected rate. but anyway, that's just me. It likely means 2% of the time, packets arrived later significantly later than the mean. (taking aspirins and guessing)   I still think chasing down that middle variance may get you closer to your 6Mbps. Especially since both tests are about 1Mbps off. If you fix it, I bet your upload will jump up too. I'm only saying that because it made such a difference for me. There are people on here that legitimately know a lot more about this than I do. I'm hoping one of them in particular will come to the rescue. What kind of router do you use ?  

rebrecs, Centurylink uses Ookla. It looks like they connect me to a server in Kansas City, Mo. to run the speed check which is only 45 miles away. The upload/download results are very close to TMN's but nowhere near as informative. I don't see a spike at the beginning of the downloads by just looking at the speed dial and I don't know what the 2ms "jitter" is that Ookla reports.      

know what happens when you run the ISP test, if you are so inclined. By the way, fixing the middle variance did make a big difference in my overall TMN results, especially on the upload side.   sorry for two posts, I hit the wrong button or something while trying to undo the caps lock    

RMcQ, yes, TestMy.Net is a great resource. I never see any ads so no telling how they get paid. Possibly selling the test results. Or maybe collecting from the ISPs for a better service resource than they have Who knows. Anyway, back to the topic, does centurylink have a speed test of their own ? If so, it is likely an Ookla based test. The results of those have to be used carefully, but they can provide an interesting data point. I ask, because you have a 5% middle variance. I spent some time fighting middle variance and it was the ISP Ookla speed test that gave me the hints I needed to finally fix it. When my TMN tests were indicating a high middle variance the ISP test was also bursty. The ISP speed test always returned perfect numbers (i.e. the full paid-for speed) but on its meter I could see the traffic stopping ans starting in bursts, which agreed with the middle variance result on my TMN speed test. My variance may have been greater than 5, and the notes are not handy. I don't know how bad the variance has to be before the bursts can be seen on Ookla. But, i WOULD LIKE TO

Throttling at the "signalling level" as you suggest seems to be a pretty good guess going by the graph that I attached.  This is typical of what I get. I just wish they would throttle at what I'm paying for.  It's like buying something that costs $9.50 total, giving them $10.00 and not getting my change back.   I have only recently discovered TestMy.net. It's a fantastic service that's being provided and has explained my irritation with Centurylink over the years. It is only recently that the service has become stable where I live (west central Missouri) so I guess they're doing something to improve with the exception of providing faster speeds.  Every Mbps counts in a rural setting.