I suspect you're seeing a decrease in the speed of data into a sink, not a decrease in end-to-end speed. Measurement results can often be puzzling here (;-))

My description of the situation is:

- an infinite (or just bloatily large) queue will accept data at just about any rate you offer it, and keep it around until the service centre can process it, which is in our case is the other end of the network link getting it. If the queue only reports ingress, it will show really large values, sometimes well above what the link can ever handle.  (Some folks report those rates as a marketing feature. I'm not sure that's exactly kosher (;-))

- a queue processes the same amount of data per unit time when latency is at a minimum as it does when it's at a maximum, so normal queues should be tuned for minimum latency.

- in TCP, there is a cost in retransmissions when we use drops to signal the sender that they've sent too much, so it's best to keep your rate just below the rate at which you get drops. That maximizes throughput for a given small latency.  TCP does this automatically when not bloatified, and on average stays really really close to the maximum speed of the channel.

- buffers are really good to smooth out brief stoppages or bursty senders, but have to be kept nearly empty to be able to do that, and then drained quickly when they get filled.

--dave (processing an email queue while waiting for a compile) c-b


On 17/08/16 04:21 AM, Alec Robertson wrote:
I'm on a TalkTalk FTTC connection in the UK, with a sync speed of 58976Kbps, via a Billion 8800NL in bridge mode to my TP-LINK Archer C7 (currently running LEDE r1348) with sqm-scripts 1.0.7-1 and mod-sched-cake 4.4.15+2016-06-29-747..5-1.

I have selected cake as the qdisc and piece_of_cake.qos as the queue setup script.

I've managed to get bufferbloat under control, with only 3-4ms of added ping when downloading but I've had to set the ingress to 43000, reducing my speed not hugely but more than I might have expected.

On the upload side I'm syncing at 10422Kbps and the egress is set to 9300, so not quite as bad. Bufferbloat here is also under control, at maybe 2-3ms when downloading.

Is there anything I can do to reclaim more of the download speed? How can I diagnose this?

The other question I would like to ask is, what's the absolute best way to see what the ping maximum actually is? With speedtest.net the ping only increases 1-2ms (pinging bbc.co.uk) and the same is true for dslreports.com (maybe a little bit higher, maximum of about 5ms) but on the dslreports.com site it says 9ms+ at times?

Thanks.

--
Alec Robertson



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-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb@spamcop.net           |                      -- Mark Twain