Assuming I never exceed the bandwidth of my connection to the internet, will enabling and configuring QoS on my router have any positive affect? I'm under the impression that QoS only helps prioritize traffic if there is congestion. If there is ample bandwidth for all traffic, doesn't all traffic flow through unencumbered?

1 Answer 1


You're right that you shouldn't need QoS if you never hit the capacity of your Internet connection, but are you sure you never hit it?

TCP is designed to transfer data as fast as the network will allow. If one of your devices is downloading a software update from a local CDN node on your ISP's network, it could use all the available bandwidth. If you were trying to do anything else on the Internet connection at the same time, you'd have congestion.

  • This was more of a theoretical question in order to address an issue we're having. Our VoIP provider insists that we need to set up QoS, but I don't think it will help because we shouldn't be anywhere near maxing out our connection. Update: For those who are interested, I believe the problem is that our ISP is providing very poor service. We've been intermittently measuring 0.5 mbps up when we're supposed to be getting 16. So, yes, QoS would probably help. But our ISP is the bigger issue.
    – rinogo
    Feb 18, 2015 at 21:23

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