[102116] in North American Network Operators' Group
Re: Cox clamping VPN traffic?
daemon@ATHENA.MIT.EDU (Mark Smith)
Sat Jan 26 02:53:41 2008
Date: Sat, 26 Jan 2008 17:51:08 +1030
From: Mark Smith <nanog@85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org>
To: nanog@nanog.org
In-Reply-To: <59f980d60801251730wa2b1699qf6c373a7ede200bf@mail.gmail.com>
Errors-To: owner-nanog@merit.edu
On Fri, 25 Jan 2008 20:30:20 -0500
"Ben Scott" <mailvortex@gmail.com> wrote:
>
> On Jan 25, 2008 7:49 PM, Jim Popovitch <yahoo@jimpop.com> wrote:
> > I see the *exact* same problem with Comcast at home. I get about 30
> > seconds of the 6.6Mbps provisioned rate then the drop kicks in and
> > down to 43kbps it goes.
>
> I suspect this is just bursting/clamping, as you suspect, but you
> may also want to investigate traffic shaping at your end. I've found
> I get much better *receive* throughput if I limit my *transmit* rate
> to less than nominal maximum. Presumably, this has to do with the
> fact that the feed is asymmetric; I can receive much faster than I can
> send, and so the send channel becomes congested and that impacts TCP
> ACK or other protocol control messages.
>
For more details,
"RFC3449 - TCP Performance Implications of Network Path Asymmetry"
http://tools.ietf.org/rfc/rfc3449.txt
Regards,
Mark.
--
"Sheep are slow and tasty, and therefore must remain constantly
alert."
- Bruce Schneier, "Beyond Fear"
