My provider had convinced me to upgrade my internet subscription to a 1Gb/100Mb connection. I had a 500Mb/50Mb connection and since it was only $1 per month extra, I agreed. For that, they had to replace my old DOCSIS 3.0 modem with a DOCSIS 3.1 modem. A Sagemcom F3896LG to be precise (with custom provider firmware).
With my old modem, whenever I dowloaded a torrent, my download speeds always maxed out (unless of course there were only a few seeds) at ~50MByte/s. But now, with the new modem, speeds max out at ~20MBytes/s no matter the number of seeds. I've done extensive testing and noticed that it isn't the speed that's being capped. It looks like the modem does some kind of "load balancing" above 20 peers. Because the speed I have as soon as I reach 20 connected peers, is the speed I keep - even if another 100 peers connect.
So for instance, I start my download. My bittorrent client starts connecting to peers and when it reaches 20 peers, my speed is (for instance) 20MB/s. That is the speed it stabilizes on. Every extra peer does not result in a higher download speed. But suppose my speed is 80MB/s when I reach 20 peers, then it stays 80MB/s.
Here is a graph that shows what is happening:
As you can see, when it reaches 20 peers, download stabilizes. And even though it climbs to 100 peers (the maximum I have set in my client), the speed never increases. It's not my connection that is maxing out. A speedtest confirms this:
So what's going on? Is this a known limitation of DOCSIS 3.1 modems? Does my provider need to change anything in the modem's settings (settings, hidden for customers)?
With my old modem, whenever I dowloaded a torrent, my download speeds always maxed out (unless of course there were only a few seeds) at ~50MByte/s. But now, with the new modem, speeds max out at ~20MBytes/s no matter the number of seeds. I've done extensive testing and noticed that it isn't the speed that's being capped. It looks like the modem does some kind of "load balancing" above 20 peers. Because the speed I have as soon as I reach 20 connected peers, is the speed I keep - even if another 100 peers connect.
So for instance, I start my download. My bittorrent client starts connecting to peers and when it reaches 20 peers, my speed is (for instance) 20MB/s. That is the speed it stabilizes on. Every extra peer does not result in a higher download speed. But suppose my speed is 80MB/s when I reach 20 peers, then it stays 80MB/s.
Here is a graph that shows what is happening:
As you can see, when it reaches 20 peers, download stabilizes. And even though it climbs to 100 peers (the maximum I have set in my client), the speed never increases. It's not my connection that is maxing out. A speedtest confirms this:
So what's going on? Is this a known limitation of DOCSIS 3.1 modems? Does my provider need to change anything in the modem's settings (settings, hidden for customers)?
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