[126176] in North American Network Operators' Group
Re: Emulating ADSL bandwidth shaping
daemon@ATHENA.MIT.EDU (Mikael Abrahamsson)
Tue May 4 15:59:02 2010
Date: Tue, 4 May 2010 21:58:29 +0200 (CEST)
From: Mikael Abrahamsson <swmike@swm.pp.se>
To: Scott Weeks <surfer@mauigateway.com>
In-Reply-To: <20100504101424.4C0F24C0@resin18.mta.everyone.net>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Tue, 4 May 2010, Scott Weeks wrote:
> "Interleaved" turned on to correct errors. This adds ~25msec between
> the CPE and the nearest router. Sometimes folks ask for it to be
> changed to "Fast". We explain that errors may cause resyncs to happen
> and then make the change if the customer still wants it. That takes the
Basically "interleaved" is a way "smearing" bits over time, so FEC can do
its job when there is a 1ms line hit that causes a lot of errors during
that 1ms.
Turning off interleaving (changing to "fast") usually means your "errored
seconds" counter will increase over time because of lack of error
correction, and your customer experiences packet loss intermittently.
Never seen it cause resyncs, but that might happen, dunno.
It is usually settable to 1,4,16 ms in each direction, so 25ms is not a
"law of nature", it's just the default 16/4 ms downstream/upstream
interleaving and then the added coding delay.
--
Mikael Abrahamsson email: swmike@swm.pp.se
