Small businesses converging voice, video and data traffic sometimes end up with haunted networks, but you can exorcise the demons. Affordable QoS mechanisms are available to oust the goblins that cause delay, jitter, bit-rate errors and dropped packets.

QoS tools use prioritization to improve a network's ability to deliver predictable service in support of specific applications and types of traffic. Traffic prioritization ensures that real-time applications, such as VoIP and video teleconferencing, get adequate service for optimal performance and other data-intensive applications aren't left in limbo.

An investment in QoS can improve the speed and quality of such applications, and reduce infrastructure and transmission costs -- an added benefit for businesses with their eyes on the bottom line.

Make your network performance howl

Although the capabilities and quality of IP solutions have advanced and their costs have decreased, the solutions are often plagued by noise and service interruptions caused by delays, jitter and dropped packets. The root cause, though, is that the core networks are ill-equipped to handle the traffic.

There are three levels of QoS tools that can remedy these problems:

• Best-effort service provides basic connectivity without prioritization of specific flows or applications, so there is no guarantee of service. A good example of this is first-in, first-out queuing, in which packets are stored when the network is congested and forwarded in the order they arrived once traffic eases.
• Differentiated service identifies and classifies traffic to assign priority and meet latency requirements within available bandwidth. This results in faster handling, more predictable service and fewer dropped packets. The network administrator predetermines the priority of specific types of network protocols.
• Guaranteed service reserves network resources for specific types of traffic. The network administrator develops bandwidth classifications, and the bandwidth is divvied up among them to guarantee availability to the highest-priority traffic while serving lower-priority traffic on a best-effort basis. This prevents low-priority flows from superseding high-priority flows.

• Classification tools. These identify and in some cases, mark packets so they can be properly managed by other QoS tools.
• Congestion avoidance tools. These prevent queues from filling and subsequently dropping packets.
• Congestion management tools. These manage the queue and flow of network traffic when bursts -- high levels of voice, video and data traffic -- occur simultaneously.
• Link-efficiency tools. These fragment large data packets and interleave real-time packets between the fragmented packets so they can be sent without delay or interference.
• Shaping/policing tools. These limit the amount of bandwidth the packets can use, to pace traffic at a controllable rate and prevent potential queue overflow.