Home Networking: How to Avoid Traffic Jams
WMM should be enabled by default. To double-check on the DIR-655, click Advanced in the horizontal menu bar, Advanced Wireless in the vertical menu, and place a checkmark next to WMM Enable. Click Save Settings to preserve any changes.
While still in the Advanced tab in the horizontal menu bar, click QOS Engine in the vertical menu bar. In the box labeled WAN Traffic Shaping, place checkmarks next to the Enable Traffic Shaping and Automatic Uplink Speed settings. The router will automatically measure the maximum speed that your ISP will allow you to upload data to the Internet and restrict outbound traffic so that it doesn't try to exceed that limit and create unnecessary contention.
Note that if your ISP is a cable company, such as Comcast, there's a chance Automatic Uplink Speed will report an inflated uplink speed because these services throttle down their uplink speeds after an initial burst. If you experience poor VoIP performance, you might need to disable Automatic Uplink Speed and enter a speed manually.
(Typical DSL uplink speeds range from 128 to 768Kbit/sec., depending on the level of service you're paying for and your distance from the phone company's central office. Cable Internet uplink speeds average about 2Mbit/sec., while fiber services such as Verizon's FiOS can top out at speeds as high as 20Mbits/sec. You can measure your download and uplink speeds using a free online bandwidth meter such as Speakeasy's Speed Test.)
In the box labeled QOS Engine Setup, place checkmarks next to Enable QoS Engine, Automatic Classification and Dynamic Fragmentation. If you have a slow uplink speed (e.g., less than 512Kbit/sec.), enabling Dynamic Fragmentation configures the router to break up large packets into smaller ones for smoother performance.
With a router that uses Ubicom's StreamEngine (see the router's documentation or manufacturer's Web site to see if this describes your router), enabling Automatic Classification allows it to automatically determine which applications should receive network priority without further intervention on your part.
If you're running a VoIP application, for instance, the DIR-655 will automatically assign high priority to protocols such as SIP (Session Initiation Protocol, used in IP telephony signaling) and RTP (Real-time Transport Protocol, used for transporting real-time data such as voice, audio, and video over IP networks), while assigning low priority to file-sharing protocols such as BitTorrent.
These types of routers have another set of QoS features called WISH (Wireless Intelligent Stream Handling). To access this feature in the DIR-655, click Advanced in the horizontal menu bar and WISH in the vertical bar.
Put a checkmark next Enable WISH to activate it. In the box labeled Priority Classifiers, place checkmarks next to HTTP, Windows Media Center (if you have PCs on your network running Windows versions that include that feature) and Automatic.
With the HTTP classifier enabled, the router will recognize most common file formats for audio and video streams (MP3, AAC, MP4, Flash, etc.) and will automatically assign them a higher priority over other data traffic traveling over your wireless network. By the same token, the Windows Media Center classifier will recognize media traffic flowing from a PC to a media extender, including Microsoft's Xbox 360. With the Automatic classifier enabled, the router will attempt to prioritize other traffic streams that it doesn't otherwise recognize, based on their behavior.
As noted earlier, not all routers offer the same QoS features or take the same approach to shaping network traffic. With the Linksys WRT600N, for instance, you access the router's quality-of-service settings by clicking the Applications and Gaming menu and then the QoS submenu. Once there, you can assign Internet access priority to specific applications or games, to specific devices according to their physical MAC address, to communication protocols and port ranges, or even to the physical Ethernet ports in the router's integrated switch.
Whichever router you happen to own, I hope the information provided here will help you tap whatever QoS capabilities it might have in order to improve your wireless networking experience.
Michael Brown, a freelance journalist living in northern California, has been writing about computers and technology since 1987. He can be reached firstname.lastname@example.org.