Here's how I explain it on our burstable T1's & T3's (We bill at the 90th percentile BTW): Burstable T1 Explanation I hope that this explanation helps: Consider that your Internet usage is probably similar to 99% of all business users. You will probably use the circuit Monday through Friday between the hours of 8am and 5pm. Utilization in the off hours and on weekends should be close to zero. This means that over an entire month (720 hours), you will have access to the circuit for only 180 hours. Remember, in that 180 hours (8am - 5pm), you will not be constantly uploading and downloading data. It is in fact quite the opposite. Internet traffic is "bursty". For example: If you are viewing a web page and you hit your enter key, data is transmitted and the image and text load. Once it is loaded, the transmission stops and you read the web page. At this point the bandwidth is again sitting idle and utilization is back at zero. This is the cycle that repeats itself during the day so it is a safe bet that your utilization in that 180 hour time frame is 50% at best. This now leaves you with 90 hours of utilization for the month. Since we bill you at the 90th percentile, this means that we will discard the highest 10% of you bandwidth peaks. The 10% equates to 72 hours. This means that we will subtract the HIGHEST 72 hours of utilization from the remaining 90 hours. This now leave you with the lowest 18 hours of utilization for the month. Again, I can't guarantee it, but it is very unlikely that your lowest 18 hours will be greater than 100k. This graph illustrates a typical business customers utilization on a T-1 circuit. http://www.intermedia.com/images/businessinternet/products/lineutil.gif Jeff Dearborn Major Account Manager Intermedia Communications Business Internet 800.993.4439 x2418 toll free 301.847.2418 direct dial 301.419.0288 fax http://www.intermedia.com/ -----Original Message----- From: Alex Rubenstein [mailto:alex@corp.nac.net] Sent: Thursday, April 19, 2001 10:09 AM To: 'nanog@merit.edu' Subject: What does 95th %tile mean? I've gotten myself into an argument with a provider about the definition of 'industry-standard 95th percentile method.' To me, this means the following: a) take the number of bytes xfered over a 5 minute period, and determine rate for both the inbound and outbound. Store this in your favorite data-store. b) at billing time, presumably on the first of the month or some other monthly increment, take all the samples, sort them from greatest to least, hacking off the top 5% of samples. Actually, this is done twice, once for inbound, once for outbound. Then, take the higher of those two, and multiply it by your favorite $ multiple (ie, $500 per megabit per second, or $1 per kilobit per second, etc). I think that most people agree with the above; the issue we are running into is one rogue provider who is billing this at in + out, not the greater of in or out. How is everyone else doing it? Specifically, larger folks (UU, Sprint, CW, Exodus/FGC, GX, Qwest, L3) Thanks!