Re: Comcast Enterprise Fiber Slow Connection Problem from TW Telecom

[John Neiberger <jneiberger () gmail com>]

Sounds like a combination of packet loss and small TCP receive windows. If
you can, grab a packet capture and make sure to get the TCP setup. That
should show you what's happening under the hood.

Also, I should mention that I totally hosed the units in my first reply.
 :)  That's what I get for hurrying.

John

On Fri, Oct 31, 2014 at 1:29 PM, Zachary Frederick <zcfrederick () gmail com>
wrote:

> 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 () 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
>
> 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 () gmail com>
> wrote:
>
> > On 31 October 2014 18:32, Zachary Frederick <zcfrederick () 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
> >
> > 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 (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 (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 (68.86.86.37)
> > 10.733
> > > ms  10.731 ms 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 (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 (69.139.168.26)
> > > 38.196 ms 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
> > > (69.139.195.18)  38.266 ms
> > >
> > >
> > > 9  (107.1.72.98)  39.781 ms  39.785 ms  39.912 ms