On Mon, Nov 26, 2012 at 9:22 AM, Michael Richardson <mcr@sandelman.ca> wrote:

>>>>> "Dave" == Dave Taht <dave.taht@gmail.com> writes:
    Dave> to move the fq_codel algorithm into the cable modem, OR to have the
    Dave> cable modem exert flow control like ADSL modems do. Then have the
    Dave> smarter device (the router) then do smarter queuing.

I was unaware that DSL models were doing this... is this with GbE
ethernet level XON/XOFF?   Should I assume that any DSL model with less
than a GbE sync doesn't/can't have it?  Any brands you'd like to
acknowledge?

We don't know that all DSL modems do this.

However, in corresponding with Michael Tremer about his results (documented here http://planet.ipfire.org/post/ipfire-2-13-tech-preview-fighting-bufferbloat), it appears that a DSL modem commonly used in Germany does implement Ethernet flow control (or he could not have gotten the results he reports there at all; all he did was turn on fq_codel on the x86 geode router he is using for IPfire).  Whether this is "standard" in DSL modems, I have no clue (anyone want to plow through DSL standards documents?).
 

I've been unable to find a supplier in the U.S. for this particular DSL modem.  Short of bidding on ebay in Europe, I was defeated (despite there being 10's of millions of them in Germany); this isn't too surprising, as the modem is supplied by the carrier in this case.

Note that I'm testing a DGN3500 this week with John Crispin (blogic) which has an integrated Lantiq DSL chip (along with Atheros radios) running fq_codel that John maintains.  That may be a better option for DSL, as it can be purchased easily via Amazon.  Wish us luck (though John's early data looks really nice).
                              - Jim


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]   Michael Richardson, Sandelman Software Works, Ottawa, ON    |net architect[
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