[colanderman]

You seem to be working under the fundamental misunderstanding that the link is the bottleneck. IT IS NOT. The ISP's router is the bottleneck, because it typically throttles the connection.

For example, my home network has a 100 Mbit bidirectional Ethernet connection between my router and my modem, and my modem has a 152 Mbps downlink (4 bonded DOCSIS channels) and an 81 Mbps uplink (3 bonded DOCSIS channels).

Neither of those is the bottleneck, because my ISP throttles my connection entirely on their router to 3.5 Mbps downstream, 1 Mbps upstream. I, like most in the US, cannot afford a 100+ Mbps home connection.

What you said would hold true IF, say, I had a gigabit connection (but still used a 100 Mbps Ethernet link). Then, yes, upstream traffic would build up in the upstream queue on my own router or modem. But that's not the case, and neither my modem nor router see anywhere near the 100+ Mbps of traffic needed to saturate the link.

If you do not understand this, I suggest looking at the queue depth on an actual router, with all traffic shaping turned off, while running a speedtest. You will see the interface queues in both directions be completely empty.

[richbhanover]

Yes, but... A "bottleneck" occurs wherever there is a high speed link going to a lower speed link. In your case, the 100 Mbps Ethernets in your home feed through the router to the 1 Mbps upstream your ISP provides. That's another bottleneck.

At this point in a conversation, I always recommend people measure their actual network, to see if they're happy with the situation. If it's good, then everyone's happy.

What results to you get from the DSLReports Speed Test (www.dslreports.com/speedtest)? It measures latency (lag) during the download and upload parts of the test, and will show if your router (or your ISP's router) is buffering too much data, and giving you undesired latency. Best regards.

[colanderman]

The 100 Mbps is from the router to the modem. There is no such thing as a 1 Mbps "link" to an ISP. That bottleneck is imposed by traffic shaping on the ISP's router and nowhere else. (An exception would be something like ADSL, where the uplink truly is the bottleneck. But even then, the queue builds up in the modem, NOT the router!)

Here's a picture, since you seem to be ignoring my words:

     150 Mbps WiFi
           |
      home router
           |
    100 Mbps Ethernet
           |
         modem
           |
    152/81 Mbps DOCSIS
           |
    +-ISP router-----------------+
    |      |  <-- QUEUE          |
    | 3.5/1 Mbps traffic shaping |
    |      |  <-- QUEUE          |
    +------|---------------------+
           |
     10 Gbps fiber (or whatever)

Or, in the case of ADSL:

     150 Mbps WiFi
           |
      home router
           |
    100 Mbps Ethernet
           |
         modem
           |  <-- QUEUE
     8/1 Mbps ADSL
           |
    +-ISP router-----------------+
    |      |                     |
    | 3.5/1 Mbps traffic shaping |
    |      |  <-- QUEUE          |
    +------|---------------------+
           |
     10 Gbps fiber (or whatever)

In either case, neither queue builds up in the home router -- that is exactly the problem, since we can't control the queue size in the modem or ISP! But by traffic shaping to 3.25/0.85 Mbps in the home router (either manually or automatically with fq-codel), we force the queues to build up there, thus giving us control.

[richbhanover]

> In either case, neither queue builds up in the home router -- that is exactly the problem, since we can't control the queue size in the modem or ISP! But by traffic shaping to 3.25/0.85 Mbps in the home router (either manually or automatically with fq-codel), we force the queues to build up there, thus giving us control.

YES! I understand what you're saying. (I had been treating the cable/DSL links and their terminating equipment as a black box; your description was being far more specific. Thanks for sticking with me to make yourself clear.)

And as you point out, the fix in all cases (at least, until our ISPs get serious about solving bufferbloat) is to force the home router to take control of the buffering by shaping the traffic a bit below the actual link speed. Thanks.