[175757] in North American Network Operators' Group
Re: Comcast Enterprise Fiber Slow Connection Problem from TW Telecom
daemon@ATHENA.MIT.EDU (John Neiberger)
Fri Oct 31 15:38:55 2014
X-Original-To: nanog@nanog.org
In-Reply-To: <22F2BA81-CB37-4805-9659-139970B12303@gmail.com>
From: John Neiberger <jneiberger@gmail.com>
Date: Fri, 31 Oct 2014 13:37:24 -0600
To: Zachary Frederick <zcfrederick@gmail.com>
Cc: NANOG Mailing List <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
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=3D1460&=
rtt=3D80&loss=3D1e-06&bw=3D25&rtt2=3D35&win=3D64&Calculate=3DCalculate
>
> 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=
=E2=80=99s
>> > 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=3D1460=
&rtt=3D38&loss=3D1e-06&Calculate=3DCalculate&bw=3D100&rtt2=3D80&win=3D64
>>
>> 3Mbps looks about right. Time for a tune up
>>
>>
>> > I have tried contacting Comcast Enterprise Tech support, however I=E2=
=80=99ve
>> been
>> > told that if I run a speed test from my connection and the test runs a=
t
>> 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 ha=
ve
>> > 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 doi=
ng
>> > 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 m=
s
>> > 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
>>
>
>
>
