Comcast Enterprise Fiber Slow Connection Problem from TW Telecom

Zachary Frederick zcfrederick at gmail.com
Fri Oct 31 19:29:56 UTC 2014


I apologize I should have said it starts out about 3 meg max and slows to about 400kpbs for most of the transfer.



> On Oct 31, 2014, at 3:27 PM, John Neiberger <jneiberger at gmail.com> wrote:
> 
> With a max bandwidth of 25 Mbps and a 40ms RTT, the max is more like 14MB/s or 1.75 Mbps. 
> 
> https://www.switch.ch/network/tools/tcp_throughput/index.html?mss=1460&rtt=80&loss=1e-06&bw=25&rtt2=35&win=64&Calculate=Calculate <https://www.switch.ch/network/tools/tcp_throughput/index.html?mss=1460&rtt=80&loss=1e-06&bw=25&rtt2=35&win=64&Calculate=Calculate>
> 
> But that's only if either endpoint is stuck at a 64 KB receive window. A quick packet capture would be able to see what was happening.  Check the TCP setup and make sure that both ends are doing TCP window scaling properly.
> 
> John
> 
> On Fri, Oct 31, 2014 at 1:02 PM, Pedro Cavaca <pmsac.nanog at gmail.com <mailto:pmsac.nanog at gmail.com>> wrote:
> On 31 October 2014 18:32, Zachary Frederick <zcfrederick at gmail.com <mailto:zcfrederick at gmail.com>> wrote:
> 
> > We have been having a problem receiving software releases from our
> > developer. The releases are typically around 1G in size. The developer’s
> > connection is a 100m metro fiber with TW Telecom,  our connection is a 25m
> > Comcast Enterprise Fiber.
> >
> > Our traffic graphs show very little utilization of our connection.
> > Typically on average we are at about 7 meg utilization of our 25.
> >
> > Every other partner that shares in our software development that receives
> > the software releases can receive the updates 3-4 times faster than we can.
> >
> > Typically we receive the releases at about 3mbps.
> >
> 
> Are you using an application that uses TCP transport for the transfer?
> 
> https://www.switch.ch/network/tools/tcp_throughput/index.html?mss=1460&rtt=38&loss=1e-06&Calculate=Calculate&bw=100&rtt2=80&win=64 <https://www.switch.ch/network/tools/tcp_throughput/index.html?mss=1460&rtt=38&loss=1e-06&Calculate=Calculate&bw=100&rtt2=80&win=64>
> 
> 3Mbps looks about right. Time for a tune up
> 
> 
> > I have tried contacting Comcast Enterprise Tech support, however I’ve been
> > told that if I run a speed test from my connection and the test runs at the
> > speed we are paying for, there is very little they are willing to look into.
> >
> > Can anyone check on the Comcast Routers on the Tracert below, or is there
> > anything that can be throttling this connection between the two connections?
> >
> > Also, our firewall and connection is able to run at the full 25. We have
> > no throttling or QOS set to prevent a good connection to our developer. For
> > example, we can run a multi-threaded upload, in the middle of the night, to
> > Amazon Glacier storage and completely saturate our connection when doing
> > so. The firewall and connection is able to handle our full bandwidth
> > capacity during that backup.
> >
> > If there is any other information I can provide to help track this problem
> > down, please let me know.
> >
> > Thanks in advance, everyone!
> >
> >
> > Trace Route below:
> >
> >
> >
> >
> > 1  (172.16.150.1)  1.143 ms  1.132 ms  1.122 ms
> >
> >
> > 2  (173.227.204.1)  1.585 ms  1.583 ms  1.574 ms
> >
> >
> > 3  chi2-pr1-xe-0-3-0-0.us.twtelecom.net <http://chi2-pr1-xe-0-3-0-0.us.twtelecom.net/> (66.192.245.166)  10.477 ms
> > 10.485 ms 10.478 ms
> >
> >
> > 4  x-eth-0-0-4-pe05.350ecermak.il.ibone.comcast.net <http://x-eth-0-0-4-pe05.350ecermak.il.ibone.comcast.net/> (75.149.230.141)
> > 10.470 ms 10.465 ms  10.457 ms
> >
> >
> > 5  he-2-1-0-0-cr01.350ecermak.il.ibone.comcast.net <http://he-2-1-0-0-cr01.350ecermak.il.ibone.comcast.net/> (68.86.86.37)  10.733
> > ms  10.731 ms he-2-0-0-0-cr01.350ecermak.il.ibone.comcast.net <http://he-2-0-0-0-cr01.350ecermak.il.ibone.comcast.net/>
> > (68.86.86.33)  12.146 ms
> >
> >
> > 6  be-10206-cr01.newyork.ny.ibone.comcast.net <http://be-10206-cr01.newyork.ny.ibone.comcast.net/> (68.86.86.225)  33.202 ms
> > 32.144 ms  32.127 ms
> >
> >
> > 7  68.86.91.30 (68.86.91.30)  41.508 ms  41.322 ms  41.599 ms
> >
> >
> > 8  te-0-0-0-1-sur01.greensburg.pa.pitt.comcast.net <http://te-0-0-0-1-sur01.greensburg.pa.pitt.comcast.net/> (69.139.168.26)
> > 38.196 ms te-0-0-0-3-sur01.greensburg.pa.pitt.comcast.net <http://te-0-0-0-3-sur01.greensburg.pa.pitt.comcast.net/>
> > (162.151.21.82)  44.644 ms te-0-0-0-0-sur01.greensburg.pa.pitt.comcast.net <http://te-0-0-0-0-sur01.greensburg.pa.pitt.comcast.net/>
> > (69.139.195.18)  38.266 ms
> >
> >
> > 9  (107.1.72.98)  39.781 ms  39.785 ms  39.912 ms
> 



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