Xfinity and AT&T disagree on what my internet speed is

@XfinityVianney​ 

I can get to Xfinity at full speed - but, after that I can't get outside of Xfinity faster than 300 Mb/s.  So, between my house and Xfinity I am OK.

Is it possible my account has been throttled accidently by Xfinity?

So, I've done some other tests.  For example, I downloaded a 2.6GB file from Microsoft OneDrive in 78 seconds - again, at around 1/3 of my Xfinity rated speed.

The thing is, I haven't found a site outside of Xfinity that downloads faster than around 300 Mb/s.

It really does look like there is something in Xfinity blocking me from downloading faster than around 300 Mb/s.  I think there is a technical problem with my Xfinity internet service.  I can get to Xfinity at full speed - but, after that I can't get outside of Xfinity faster than 300 Mb/s.

PS C:\Users\smith> tracert yahoo.com

Tracing route to yahoo.com [2001:4998:24:120d::1:0]
over a maximum of 30 hops:

  1     <1 ms    <1 ms    <1 ms  Smith ip address
  2     9 ms     8 ms     8 ms  Smith connection to Xfinity ip address
  3    14 ms     8 ms     8 ms  po-308-1251-rur201.royalton.tx.houston.comcast.net [2001:558:2c2:6011::1]
  4     8 ms    10 ms    11 ms  po-2-rur202.royalton.tx.houston.comcast.net [2001:558:2c0:110::2]
  5     *        *        *     Request timed out.
  6    10 ms    10 ms    10 ms  2001:1900:5:3::315
  7    53 ms    53 ms    53 ms  2001:1900::3:197
  8    60 ms    60 ms    60 ms  YAHOO-INC.ear3.Seattle1.Level3.net [2001:1900:2100::1632]
  9    62 ms    59 ms    59 ms  ae-10.pat2.gqb.yahoo.com [2001:4998:f007:200::1]
 10    57 ms    57 ms    57 ms  et-18-0-0.msr2.gq2.yahoo.com [2001:4998:f00f:20f::1]
 11    57 ms    57 ms    57 ms  et-1-1-0.clr1-a-gdc.gq2.yahoo.com [2001:4998:24:fc00::1]
 12    57 ms    57 ms    57 ms  2001:4998:24:fa06::1
 13    57 ms    61 ms    57 ms  et29.usw1-1-lbc.gq2.yahoo.com [2001:4998:24:d210::1]
 14    59 ms    56 ms    57 ms  media-router-fp73.prod.media.vip.gq1.yahoo.com [2001:4998:24:120d::1:0]

Trace complete.
PS C:\Users\smithr>

Using tracert, it looks like there is something wrong at:

po-2-rur202.royalton.tx.houston.comcast.net [2001:558:2c0:110::2]

for example.

Thanks

Houston, TX

@truerock2​  What Xfinity calls "speed" isn't what you think it is.  What is the "up to speed"?  That's a theoretical calculation based on the number of DOCSIS channels aggregated together.  It's actually bandwidth -- the amount of ones and zeros you can slam down the pipe at the same time.

All bets are off when you talk to a website.  It depends on quite a few things, but largely how they handle traffic on their own servers.  If you want to actually measure bandwidth, what you would use is a benchmark utility that can pull data from multiple sources using threaded workers that can independently establish connections to remote locations.

Then, provided you are using enough workers, and your hardware can handle the memory, CPU and disk traffic load, you could get an idea of what bandwidth you are actually getting.  If your hardware can't do it, then you would need several clients to all download at the same time.  Remember on a 1Gbps ethernet port, you are really going to be able to get real world throughput of around 940-960Mbps, depending on the hardware and software overhead.

What that means is "Speed", doesn't make any given web page load faster.  In fact, you'd see the same performance on a 400Mbps plan as you would a 1Gbps plan.  What it means is aggregated traffic may be able to achieve an "up to" throughput.  

Thanks...

But to re-clarify...

I can get 900 Mb/s from Xfinity - so, everything from my PC to Xfinity is OK.

Testing at dozens of gold-standard datacenters around Texas all download to my PC at around 300 Mb/s.

Tracert indicates that Xfinity has a problem at its out-bound router.

I'm guessing Xfinity has accidently throttled my account.

And to be clear, I have had 900 Mb/s download speed for years with only occasional problems.  This current problem started a few months ago and I thought it might go away - but, it has not.

@truerock2​  You might have a bottleneck problem, or an oversubscribed neighborhood, or it's just the ICMP traffic is dropped when load conditions are high, and not everything will respond to a ping.  That's pretty common, ICMP isn't very reliable in general, and a lot of us don't enable the protocol at all on our firewalls.  You'll see that a lot with cloud VPS gateways too.  You'll also find traffic shaping happening on just about everyone's server/public facing services to mitigate DoS attacks, as well as set limits on services, which is why actual bandwidth testing using multiple remote sources will give you a better idea of what you can really get.    

If you are trying to see if an endpoint is alive or not, and a route there, try nmap with -sT for a tcp connect scan, or -sT --traceroute -p [port] [destination] if you want to see what's in the middle.  Scan a single port, not multiple ports because you'll also trip dynamic firewall protections by hitting multiple ports from the same source.  You might end up running into issues with their cloud edge "advanced security" too if you are using xfinity gear, so consider disabling the net nanny too.

I'd also add, try it with a different OS too.  You might get a vastly different result due to a local OS bottleneck.  Ubuntu DVD?  Sure, why not, but watch the memory usage and I/O performance for a jam up there.   

Thanks for providing those details @truerock2. Send us a direct message with your full name and full service address so we can take a look and see if we notice any issues on our end. 

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