Home Networking: How to Avoid Traffic Jams

Artwork: Chip Taylor
In many households today, broadband Internet connections are used not only for e-mail and Web browsing, but also to stream music and video, play online games and/or perhaps make voice calls using a VoIP (Voice over Internet Protocol) service.

You may have several PCs on your home network, as well as some combination of a gaming console like the Xbox 360, an iPhone or other handheld device, and perhaps a streaming music player such as the Squeezebox or a streaming video player such as the Roku. While some of these devices may have a wired connection to your router, most tap in wirelessly.

So what happens when one person wants to listen to music, another wants to watch a movie and still another wants to play an online game all at once? If you've never tweaked your router's firmware, you might experience performance problems. What's more, many wireless routers leave the factory with some of their best features disabled. I'll show you how to change your router's configuration so that you can take full advantage of its capabilities.

Why router settings matter

By default, a wireless router maximizes the rate at which it transfers data. This is desirable when you're transferring files from point A to point B using a protocol like TCP because you want to move files as fast as possible. If the router begins dropping too many packets, it simply throttles its link rate down until the packet loss abates -- and then it begins ramping up all over again.

Dropped packets and seesawing link rates aren't a big deal when you're downloading files from the Internet or moving them around your local network because the packets are automatically resent. It also doesn't matter if some packets arrive out of order, because you're not going to access the file until the data transfer is complete anyway.

Dropped and out-of-order packets are a big problem, however, if they occur while you're streaming a movie, listening to music, or speaking to someone using a VoIP service like Vonage or Skype. Applications such as these require a sustainable link rate with as few dropped packets as possible; consistency is the key here, not raw speed.

Sending high-definition video from a PC in your den to a media player in your living room, for instance, typically consumes between 20 and 25 megabits per second of network bandwidth. That shouldn't a problem for today's 802.11n routers, which promise theoretical bandwidth of up to 300Mbit/sec.In reality, problems such as dropped packets, out-of-order packets and jitter (packets arriving at different rates of speed) can cause pixilation, stuttering, visual dropouts, soundtracks losing sync with video, and all sorts of other problems.

Concurrent traffic on your network also has an impact. You probably won't enjoy watching a movie streamed from Netflix if your teenager is exchanging massive files using BitTorrent at the same time, for instance.

Fortunately, there is a solution that delivers optimal performance for everyone in the house. Unless your router is very old, it has firmware settings that can be configured to instruct it to assign packets associated with streaming media traffic (music, video, games and the like) a higher priority than packets associated with data-file traffic (documents, spreadsheets, digital photos and so on), based on the assumption that these data types aren't as time sensitive.

These settings are collectively known as "quality of service" (QoS). Enabling and tweaking QoS settings is a balancing act: It can make some network-oriented applications run more smoothly, but only at the expense of other applications. It is, however, the best means of allocating your network's bandwidth.

Unfortunately, there is no standard user interface for changing QoS settings. The Wi-Fi Multimedia (WMM) specification, which is supported by nearly every modern router, is supposed to prioritize network traffic according to four access categories: from highest to lowest priority, these are voice, video, best effort and background. In order for this to work, however, WMM must be enabled in both the router's firmware and in the client's Wi-Fi adapter.

In addition, each application (such as the media server in a network-attached storage box) must embed two bits in each packet to inform the router of its priority. However, few real-world applications other than VoIP services embed these bits, which renders WMM rather useless for applications other than voice. And that's why you'll need to tweak your router's QoS settings on your own. Here's how.

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