[154321] in North American Network Operators' Group
Re: How do the lowest layers of the DSL stack work?
daemon@ATHENA.MIT.EDU (Stefan Bethke)
Mon Jul 2 07:26:47 2012
From: Stefan Bethke <stb@lassitu.de>
In-Reply-To: <CAAWx_pU+txcudQowhMtQx8mhEBQVRhx6O_iQ6fx05Kvzh9otxA@mail.gmail.com>
Date: Mon, 2 Jul 2012 13:25:43 +0200
To: James Bensley <jwbensley@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Am 01.07.2012 um 21:01 schrieb James Bensley:
> [15.24 Mbit/s raw bit rate compared to 8.128 Mbit/s net] is quite a =
drop in speed and I'm trying to understand where this is happening.
...
> According to that extract, it all disappeared because of =
[Reed-Solomon] encoding, which is hugely vague.
http://en.wikipedia.org/wiki/Reed-Solomon_error_correction#Data_storage
The second paragraph explains that typically the raw bit rate is twice =
the net rate.
The raw bitstream is then encoded further as HDLC or ATM.
Stefan
--=20
Stefan Bethke <stb@lassitu.de> Fon +49 151 14070811
