By default, all packets of data traveling across a local-area network (LAN) are created equal. If all of the traffic on a network is text- or file-transfer-based, the system is workable--and no one notices when a 40MB file is delayed by 50 milliseconds as more bandwidth is made available to all users and applications.
If one type of application on a network is dramatically different from the others and requires far more bandwidth, however, problems can occur. The most common examples involve Voice-over Internet Protocol (VoIP) phone service and streaming video.
Data packet delays can introduce out-of-sync sound and jittery, pixelated images, or worse. Left uncorrected, such a system may deliver smooth video on some occasions, and awful video on others. One way to stack the odds in your favor is through Quality of Service (QoS) capabilities.
QoS is networking à la George Orwell's "Animal Farm": Some data packets are more equal than others. The preferred packets will be at the top of the queue when passing through a network port, while lesser packets cool their heels. The result is smoother audio and video presentation, even when the network is humming with file transfers and general business traffic.
How to Know If You Need QoS
Whether you need QoS depends on the mix of applications that run on your network. Whether you can achieve it depends on your network infrastructure's capabilities. Let's look at each of these factors.
For the vast majority of network users, QoS boils down to making sure that voice and video applications perform well. If your company's only voice calls occur over Skype and involve personal communications, and if its only video use consists of YouTube downloads viewed during employee breaks, then QoS isn't worth the bother.
On the other hand, if you use VoIP as your standard office phone system, or if you want to make extensive use of videoconferencing to replace business travel, proper attention to QoS can significantly upgrade employee productivity and your company's perceived quality in the marketplace. But how do you establish QoS on your network?
Getting Started With QoS
QoS has a specific set of meanings in networking, and it's distinct from various things you can do to improve the overall performance of the network. (At the end of this article we'll look at ways to boost network performance.)
In most instances, small businesses will see QoS established in the network's router, and perhaps elsewhere. If you dive deeply into the internal structures of network traffic, you'll find two basic flavors of QoS: Integrated Services (IntServ) and Differentiated Services (DiffServ). IntServe permits relatively fine-grain control of traffic streams and tends to be used within small networks or between closely related networks. The DiffServe protocol works on a less precise basis and most often is used between service providers and Internet backbone companies.
For small businesses, however, the critical distinction is between "simple" and "complicated" QoS. The difference relates to the software on the router itself. Some routers, such as the Linksys WRT54G, provide tabs in the setup application where you can turn on QoS and give priority to traffic streams based on applications, ports, or Media Access Control (MAC) addresses.
The easiest path to QoS in this simple situation is to turn on QoS, select 'applications' as the basis for priority, and then designate VoIP and video-conferencing applications to receive high priority. Thereafter, the router will give traffic streams priority based on application information contained in the headers of the data packets.
Because many VoIP services use different ports for traffic at different times, basing QoS on ports can demand considerable network monitoring and application knowledge. MAC address-based QoS is valuable if all of your voice or video traffic comes from one or two computers, but it's far more restrictive than the application-based option.
Routers intended for the small-enterprise market allow for more-precise QoS control, at a cost of far greater complexity in setting up the rules for quality. Such complicated routers--from companies like Cisco--enable you to conduct network monitoring and analysis and then use the results to make QoS data-priority decisions based on the ports and protocols of traffic between specific addresses. If this type of router sits at the heart of your business network, either your trained network staff or a third-party network engineer with solid experience in QoS should take over.
Overall Network Performance
Without getting caught up in formal QoS processes, you can do several things to improve the overall performance of your network--and of your VoIP and video services along with it. For instance, you can automate backup processes and regular large-file transfers to occur late at night, when fewer people are in the office; you can create an environment that limits mass e-mailing of the latest YouTube cat video; and you can suggest that not every call needs to employ high-def, large-screen video.
On the hardware side, many Wi-Fi access points will switch all users to a lower-performing standard (such as 802.11b) if any user attaches at the slower speed. Ensuring that all company laptops use the latest, highest-performing wireless protocol will help keep everyone moving data along more quickly. In many cases, moving away from wireless entirely is the best answer. If your company's workspaces can accommodate cabled connections, encourage users to plug in to reduce the load on the wireless network.
Of course, each workstation, whether portable or not, should be fully equipped with RAM and well maintained, with all software fully patched, hard disks defragmented (if the operating system supports and requires this), and each computer's sound and video systems matched to the correct drivers. These steps will contribute to better performance for VoIP, video, and other applications.
Properly handled, QoS can make an immediate difference in the quality of VoIP calls and videoconference meetings. The audio and video streams will be smoother, jitter and artifacts will be reduced, and the overall user experience at both ends will dramatically improve. Adopting these common-sense network and computer optimization tips will yield significant improvement at little or no capital cost.