You can use a small fraction of the capacity of the cable uplink path to
measure its queueing delay dynamically, and when it gets longer than
latency*"expected bitrate", reduce "expected bitrate".
You want to do this *as quickly as possible*, so what you do is insert a "link
monitor" task in the driver that sends tiny probe packets addressed to the
nearest "loopback point" you can find/create on the other side, and measure the
RTT. You can use, for example, the technique used by traceroute, which is to
set the hop count to the smallest number that causes a return ICMP packet to be
sent, and send one of those periodically.
I used this specific technique to cause my uplink queue to move back into my
router, where I could manage it. You can also use it for the downlink queue
measurement, but it doesn't move the queue into the router smoothly, instead
you have to drop/ECN-mark the IP frames coming in.
This can all be done between the IP layer and layer 2. Since it exploits
speedboost better, it might be worth adding as an option to cerowrt, so you
don't have to set a speed limit explicitly when you have a single connection to
the public Internet.
-----Original Message-----
From: "Michael Richardson" <[email protected]>
Sent: Monday, November 26, 2012 9:22am
To: [email protected], [email protected]
Subject: Re: [Cerowrt-devel] [Cerowrt-users] QOS settings vs speedboost and
random bandwidth
>>>>> "Dave" == Dave Taht <[email protected]> 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?
--
] He who is tired of Weird Al is tired of life! | firewalls [
] Michael Richardson, Sandelman Software Works, Ottawa, ON |net architect[
] [email protected] http://www.sandelman.ottawa.on.ca/ |device driver[
Kyoto Plus: watch the video <http://www.youtube.com/watch?v=kzx1ycLXQSE>
then sign the petition.
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