D-Link DWS-4026 Product Manual - Page 325

Software User Manual 12/10/09 D-Link Unified Access System Section 5: Configuring Quality of Service This section gives an overview of Quality of Service (QoS) and explains the QoS features available from the Quality of Service navigation tree menu. This section contains the following subsections: • "Configuring Differentiated Services" • "Configuring Class of Service" • "Configuring Auto VoIP" In a typical switch, each physical port consists of one or more queues for transmitting packets on the attached network. Multiple queues per port are often provided to give preference to certain packets over others based on user-defined criteria. When a packet is queued for transmission in a port, the rate at which it is serviced depends on how the queue is configured and possibly the amount of traffic present in the other queues of the port. If a delay is necessary, packets get held in the queue until the scheduler authorizes the queue for transmission. As queues become full, packets have no place to be held for transmission and get dropped by the switch. QoS is a means of providing consistent, predictable data delivery by distinguishing between packets that have strict timing requirements from those that are more tolerant of delay. Packets with strict timing requirements are given "special treatment" in a QoS capable network. With this in mind, all elements of the network must be QoS-capable. The presence of at least one node which is not QoS-capable creates a deficiency in the network path and the performance of the entire packet flow is compromised. Document 34CSFP6XXUWS-SWUM100-D7 Configuring Quality of Service Page 325