Do I Need To Worry About Traffic Management or QoS On My Router?

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Peter asks: Since I intensively use my bandwidth for multiple purposes, including VoIP (Vonage), Skype, Web browsing, Streaming video (DLNA or YouTube) and sometimes even gaming (PS3), I was looking for a modern QoS (Quality of Service - internet traffic prioritization) featured Wireless router with good signal strength/coverage. I like the features of Apple’s AirPort Extreme routers, but they lack QoS features. What do I need to know?


Peter, there are a few things to note about most consumer-grade (i.e. sub $500) routers. In my experience:

  1. They all do some sort of QoS/packet-shaping/congestion control internally anyway (see this this discussion of “TCP Vegas”)
  2. Enabling true QoS in consumer-grade routers that support it is often met with less than desirable results. I think this is because of the CPU speed in most of these routers, or perhaps the “cheap” QoS algorithms they employ. Whatever the case, it’s often just not worth the trouble.

On top of all this, most of our cable modem connections are “burstable”, meaning we can have access to a short period of increased bandwidth at the start of any transfer, then it slows down to our “official” speed. Enabling QoS means you have to set your router to use 95% of your lowest maximum speed in order to ensure overhead room, meaning you’ll never see the benefits of burstable bandwidth.

For example: if you have a 10Mbps connection that can burst all the way up to 20Mbps, you’d need to set QoS to a maximum of 9.5Mbps in order to leave it room to do its magic. Because of this, your router would never let you see the 20Mbps bursts.

In short, I don’t think QoS is necessary or worthwhile for most home and small office users, and I’ve never had a need for it here at my home-office (running DD-WRT on a Dual Band Linksys WRT600N).

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Also, there are different forms of QoS.

The simplest forms are something like DSCP.  This doesn’t “reserve” bandwidth at all; it simply prioritises packets so packets with certain tags get forwarded before others.  Of course, this requires that the senders tag their packets, and won’t help you on download.

Other QoS algorithms actually carve up the available bandwidth.  If you don’t have a reservation, you can’t play.  Which in practice means that you never use all your bandwidth.  Again, for this to work, it requires that the other end is also using the same rules.

Most of the time, in a really small network, you’ll get better results by simply turning high-bandwidth using connections off if you notice performance degradation.

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