Stumbled across a great tool...

[DocGreen]

I upgraded my Comcast modem tonight to take advantage of their new faster Blast internet speeds. Their advertisements claimed that I should be getting 50Mbps downstream, but after upgrading to a DOCSIS 3.0 modem I was still only getting 25-30Mbps according to speedtest.net. I was starting to think that Comcast had screwed up and was only giving me "Performance" speeds instead of "Blast," and that left me ready to demand a bill credit. Before calling them to raise hell I did a bit of searching and came across a handy little tool that was able to put my mind at ease:

ShaperProbe: http://www.cc.gatech.edu/~partha/diffprobe/shaperprobe.html

The idea behind this tool is to determine if your ISP is using traffic shapers to limit your bandwidth. The added bonus is that it will also give you an accurate reading of your maximum and median speeds. Open the Windows Resource Monitor to the Network tab while running ShaperProbe for even more insight into your connection speeds!

Using this tool, I as able to determine that I was actually getting a median of 54Mbps downstream, and that speedtest.net was just plain wrong. I was also able to see using the Resource Monitor that my bandwidth actually peaked (for only a few seconds) at around 98Mbps... Now I'm curious to see if it would go higher if I used a computer with a gigabit NIC.

 

[YeOldeStonecat]

What operating system are you using? If you have XP, you probably want to do some tweaking of the TCP stack to get the most out of the higher speeds of Docsis 3. Bump RWIN up quite a bit for example, and ensure MTU is at 1500. Vista and Win7 have auto tuning and do quite well by default...but may want to check your system anyways, something may have been thrown out of whack.
http://www.speedguide.net/sg_tools.php

Some of our tools in above link.

 

[DocGreen]

What operating system are you using? If you have XP, you probably want to do some tweaking of the TCP stack to get the most out of the higher speeds of Docsis 3. Bump RWIN up quite a bit for example, and ensure MTU is at 1500. Vista and Win7 have auto tuning and do quite well by default...but may want to check your system anyways, something may have been thrown out of whack.
http://www.speedguide.net/sg_tools.php

Some of our tools in above link.

Thanks Stonecat, somehow that slipped my mind last night I'm running 7 on all my computers, but I do still use that handy little TCP optimizer in D7.

*edit* Just realized that D7's using your SG TCP Optimizer, LOL

 

[DocGreen]

Where do I manually set the RWIN?

Current value is 65700, but all the calculators say it should be something like 1027840.

 

[Frick]

If you are not getting the new Comcast speeds check your router and see if you or anyone else setup qos, as that will limit the bandwidth to the levels previously set (not the new speeds).

I also had an issue and they believe the cause was my old cable modems on my Comcast account. While everything appeared to be setup correctly on their end, the boot file for the new speeds was not actually getting pushed to my new cable modem. It appears the info from the old modems was overtaking priority and my new modem would never correctly update. To fix this they added numerous place holders or empty modem spots below my new modem, but above the old modems. After this was done I finally got the new speeds.

The simple solution would seem to be to have them remove the old modem info, but apparently they are not able to do that......

 

[DocGreen]

If you are not getting the new Comcast speeds check your router and see if you or anyone else setup qos, as that will limit the bandwidth to the levels previously set (not the new speeds).

I also had an issue and they believe the cause was my old cable modems on my Comcast account. While everything appeared to be setup correctly on their end, the boot file for the new speeds was not actually getting pushed to my new cable modem. It appears the info from the old modems was overtaking priority and my new modem would never correctly update. To fix this they added numerous place holders or empty modem spots below my new modem, but above the old modems. After this was done I finally got the new speeds.

The simple solution would seem to be to have them remove the old modem info, but apparently they are not able to do that......

Router is brand new... no QoS. My problem was just that speedtest.net was giving me an inaccurate reading.

 

[Markverhyden]

Router is brand new... no QoS. My problem was just that speedtest.net was giving me an inaccurate reading.

I never use just one speed test site. Had too many issues with misreporting in the past. But thanks for that tool tip.

 

[Rosco]

nice tool doc... thank filllllllller

 

[rsarceno]

Nice tool and thanks.

I wouldn't say speed test is wrong. When ISP is setup with QOS, (Traffic Shapping, priority queuing, WRED, etc), the additional bandwidth or blast rely on the following conditions.

1. First thing is banking process.. Let say you have a guarantee rate of 30mb with a max speed of 50MB. The first 60 seconds, you used up 30MB, then next 60 seconds you didn't use the internet. So you just bank 30mb. This means on the next 60 seconds you can have 50mb and after that you can have 40mb.
   
2. How much can you bank? Just because you didn't use the internet for hours, doesn't mean you have that much savings. The banking has max or expiration.
   
3. And third, available shared bandwidth. Even if you have something in the bank, you might not get the additional speed if there is no available bandwidth. During busy hour, the chance is very slim.

With the speed test available on the internet they use averaging. This is the value that you want to use when calculating your VoIP bandwidth allocation and etc. You want guaranteed and not MAX bandwidth.

Don't get me wrong, I like blast but just can't depend on it.

 

[DocGreen]

Nice tool and thanks.

I wouldn't say speed test is wrong. When ISP is setup with QOS, (Traffic Shapping, priority queuing, WRED, etc), the additional bandwidth or blast rely on the following conditions.

1. First thing is banking process.. Let say you have a guarantee rate of 30mb with a max speed of 50MB. The first 60 seconds, you used up 30MB, then next 60 seconds you didn't use the internet. So you just bank 30mb. This means on the next 60 seconds you can have 50mb and after that you can have 40mb.
   
2. How much can you bank? Just because you didn't use the internet for hours, doesn't mean you have that much savings. The banking has max or expiration.
   
3. And third, available shared bandwidth. Even if you have something in the bank, you might not get the additional speed if there is no available bandwidth. During busy hour, the chance is very slim.

With the speed test available on the internet they use averaging. This is the value that you want to use when calculating your VoIP bandwidth allocation and etc. You want guaranteed and not MAX bandwidth.

Don't get me wrong, I like blast but just can't depend on it.

Just wanted to add that after a couple days, Speedtest.net started showing "correct" results. Not sure what the deal was...

 

[UCanFixit]

Now I'm curious to see if it would go higher if I used a computer with a gigabit NIC.

Yep! If you are gigabit all the way through (eg, computer, router, modem) then you would most likely realize that full 50mbps potential. In fact, I recently had a similar situation where my PC and modem were gigabit capable but my router only had a 100MB port. So, that bottleneck was reducing my "wired" ethernet connection speed from a full 50mbps down to about 35mbps. Now, one would think that a 100mb port should handle the 50mbps speed but it didn't! However, once I added the gigabit-capable router to the mix, my download speeds increased to a whopping 55mbps!