[Bloat] [Codel] [Cerowrt-devel] FQ_Codel lwn draft article review

Alex Burr ajb44.geo at yahoo.com
Thu Dec 6 15:41:00 PST 2012


> From: Dan Siemon <dan at coverfire.com>

> My VDSL2 modem (Alcatel Cellpipe 7130) shows:
> Upstream line rate: 7344 kbps
> Bearer Upstream payload rate: 6560 kbps
> 
> Can you shed some light on what causes the difference? Is it the 65/64
> encoding and error correction overhead? I assume this does not take into
> account things like the 802.3 header.

Well, a modem can say anything it likes, but 'bearer' is the term in the standard for the layer
below PTM or ATM. So the difference probably includes error correction overhead, and a little bit for 
the two modems to talk to each other, but not either 65/64 encoding or 802.3 headers, both of which 
subtract off the 6560 kbps.

In theory, the line rate can also be split between multiple bearers.

Alex


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