[175761] in North American Network Operators' Group
Re: Comcast throttling?
daemon@ATHENA.MIT.EDU (Justin M. Streiner)
Fri Oct 31 16:00:24 2014
X-Original-To: nanog@nanog.org
Date: Fri, 31 Oct 2014 16:00:01 -0400 (EDT)
From: "Justin M. Streiner" <streiner@cluebyfour.org>
To: "nanog@nanog.org" <nanog@nanog.org>
In-Reply-To: <CACBmxzf1wD8fzDkzOM4bx=DO2GiQoS0vO-m0eYCjD+aoDpFSyg@mail.gmail.com>
Errors-To: nanog-bounces@nanog.org
On Fri, 31 Oct 2014, Mark Price wrote:
> Similar to another thread on the list today, I'm troubleshooting a problem
> for a customer on Comcast business fiber.
>
> Downloading a file from one of our web servers is very slow (~15KByte/sec).
> mtr looks clean in both directions. I added an IP address on the same
> server from a different class C on our network, and downloads form this new
> IP are fast (2MByte/sec).
>
> Tracerouting from server to client is the same using both source IPs. But,
> one IP consistently has the very slow speeds that the other does not.
> Changing our outbound path between different upstreams does not make a
> difference.
>
> It certainly feels like Comcast is throttling one of our IP ranges. Could
> someone at Comcast please contact me off-list for details?
That's possible, but while a traceroute can help shed some light on
certain performance problems, this doesn't seem like one where a
traceroute will help very much. The slow traceroute hops are more likely
due to other factors (ICMP rate limiting / control plane policing / etc),
rather than a direct indicator of Comcast shaping / throttling your
traffic.
As others have indicated, doing a packet capture of a transfer session
that shows the behavior you noted is likely to be a lot more telling than
a traceroute.
jms
