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I have a Huawei HG658 modem/router combo, provided by my ISP, which is a little bit old and does not support/feature Smart Queue Management (SQL) that helps eliminate bufferbloat issues.

When about 80% of my bandwidth is utilized, bufferbloat kicks in and ping/latency increases which is expected in this case.

Does bufferbloat happens at a certain capacity speed, or when bandwidth is operating at like 70% at whatever internet speed?

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  • It happens at the point that you exceed the router specifications. Even if your router has 1 Gbps interfaces, the router probably maxes out at considerably less than that. Even business-grade routers like the Cisco 4331 with three 1 Gbps interface built-in, and slots for more interfaces, will top out at 100 to 300 Mbps, depending on the features configured.
    – Ron Maupin
    May 22, 2018 at 13:27
  • Good. Then for example, if I had 10 Mbps and my bufferbloat happens at 8 Mbps, does that mean even if I upgrade my plan to 20 Mbps, it will still happen at 8 Mbps?
    – tuki
    May 22, 2018 at 13:29
  • That would be a good assumption.
    – Ron Maupin
    May 22, 2018 at 13:31
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    Bufferbloat is exclusively about congestion, wherever that may come from. There are plenty of resources on Bufferbloat. I suggest you look at some and then ask a more specific question about stuff you don’t get.
    – Daniel B
    May 22, 2018 at 13:50

1 Answer 1

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Bufferbloat most frequently occurs when your connection to your ISP is busy/saturated/congested. It seems you're seeing it when you hit 80% of the link capacity.

Whenever there's congestion, the router begins to queue up the packets to be sent. If the congestion goes away quickly (because the sender stops/slows down), the queued packets get sent pretty soon. But if the congestion continues (say, for tens or hundreds of milliseconds) those packets remain in the queue until it's their turn to be sent. Those milliseconds are added to the packet's latency, and give you Bufferbloat.

It is the router's responsibility to detect this situation, and to slow down the sender(s) that are filling the packet queue. Smart Queue Management (SQM) does this using the fq_codel or (the newer) cake qdisc.

What about getting a faster link from your ISP? It may not help. Here's why:

Your faster line really will move more data. But your senders (the uploading/downloading computers on your network) always strive to saturate the link to the ISP, leading to congestion (again). So the router will still be likely to queue packets, leading to bufferbloat.

The right solution is to get a router that that can offer feedback to the senders to slow down when there's congestion. For an intuitive description of the problem, see my blog post Bufferbloat and the Ski Shop

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  • Linking to your own blog is fine per se, but you need to be explicit about it. See How not to be a spammer.
    – tripleee
    May 23, 2018 at 11:43
  • Fair enough - thanks for adding the note about it being my blog posting. May 23, 2018 at 17:01
  • Thank you so much for the detailed answer. I have also read your blog post, and I pretty much understood everything. Last question, there are some internet services that limit how much bandwidth can be used, especially like online games. So, if we assume that we have 10 Mbps down/up, and the game in question only uses about 64 kbit/s up and down, so in this case the router should not suffer from Bufferbloat?
    – tuki
    May 27, 2018 at 13:51
  • Not quite. Even if your game only uses 64 kbps up/down, the router can buffer too much data if other programs (or computers) are sending or receiving data. May 29, 2018 at 2:05

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