A few months ago, I decided to try out Clear Wireless WiMax as they offer ‘unlimited’ 6Mbs down over WiMax (refer to Clear WiMax in Atlanta, Clear WiMax Intial Review, and Clear WiMax Follow-up). However, after a few weeks, I started receiving notices that I was using too much bandwidth (see Clear ‘Unlimited’ Plans and Clear Usage Addendum).
More recently these warning letters have ceased with no explanation.
A few notes about WiMax; it is a very moody connection: often I can get speeds of up to 8Mbps, but other times I am stuck at around 2Mbps (rotating the router an inch or so left/right usually resolves this). During a rainstorm, my speed tops out at about 3Mbps, but with a wide range of variance (4Mbs down to 500kbps). The result of this bandwidth ‘feature’ it is very often hard to figure out what the heck is going on.
Today I tweaked with my bandwidth monitor (NetLimiter) to try to see if there are any traffic shaping/throttling patterns.
- One obvious pattern is that if I use my full bandwidth for 10 minutes, by speed drops to 1Mbps (about 125kB/sec). If I disconnect for about 15 minutes and reconnect, the bandwidth returns to full speed.
- If I run full speed for 9 minutes, cap my downloads to 1Mbps for 9 minutes and then go back to full speed, I will top out at about 1.9Mbps and 10 minutes later it drops to 1Mbps.
- When I set my download limit to about 3.6Mbps (450kB/sec), I do not see any throttling after 25 minutes at this speed.
- After about 9pm at night, there does not appear to be any bandwidth throttling
It could be my imagination or it could be an incredible coincidence, but I believe that Clear Wireless is doing bandwidth throttling in the Atlanta, GA area. While I am not overly concerned as I am using WiMax as a secondary connection, it would be very nice to know the stipulations of this traffic shaping if this actually being enforced!
Update: It also appears that this is only being used during peak hours- and the 'peak hours' are not always the same. Yesterday (Sunday), there did not appear to be a cap in place until around 5pm. This limited me to 1Mbps if I used any amount of bandwidth for over 10 minutes. It ended around 11:00pm. Perhaps this is an automated system that starts limiting connections when a WiMax tower is being saturated?
Update 2: Pretty much the same as before; bandwidth caps occur between 5pm to 11pm and not on Sunday- but I noticed that the caps are at different levels on different occasions; sometimes 1Mbps, others 2Mbps, etc. This does appear to be some sort of 'auto throtting' that kicks in- perhaps when the WiMax tower is saturated?
Another interesting note is that rebooting the modem usually clears the limit (until the 10 minute timeout expires); so I would guess the cap is per session and not per device (and rebooting establishes a new session)?