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For example, time-sensitive multimedia and VoIP are given effectively higher priority for transmission
(lower wait times for channel access), while other applications and traditional IP data which are less time-
sensitive but often more data-intensive are expected to tolerate longer wait times.
Note:
Regardless of the QoS settings, the AP/Bridge always prioritizes packets identified with
the SpectraLink Radio Protocol type in the IPv4 header for SpectraLink® Voice Priority
(SVP) operation.
The Vivato Wi-Fi AP/Bridge implements QoS with a custom extension to the traffic control mechanism in
the Linux kernel. Our Linux-based queuing class is used to tag packets and establish multiple queues. The
queues provided offer built-in prioritization and routing based on the type of data being transmitted.
The VivatoVision UI provides a way for you to configure parameters on the queues.
QoS Queues and Type of Service (ToS) on Packets
QoS on the Vivato Wi-Fi AP/Bridge leverages existing information in the IP packet header related to Type
of Service (
). Every IP packet sent over the network includes a ToS field in the header that indicates
how the data should be prioritized and transmitted over the network. The ToS field consists of a 3 to 7 bit
value with each bit representing a different aspect or degree of priority for this data as well as other meta-
information (low delay, high throughput, high reliability, low cost, and so on).
For example, the ToS for FTP data packets is likely to be set for maximum throughput since the critical
consideration for FTP is the ability to transmit relatively large amounts of data in one go. Interactive
feedback is a "nice-to-have" in this situation, but is less critical. VoIP data packets are set for minimum
delay because that is a critical factor in quality and performance for that type of data.
The AP/Bridge examines the ToS field in the headers of all packets that pass through the VA4200. Based
on the value in a packet’s ToS field, the VA4200 prioritizes the packet for transmission by assigning it to
one of the queues. This process occurs automatically, regardless of whether you deliberately configure
QoS or not.
A different type of data is associated with each queue. The queue and associated priorities and
parameters for transmission are as follows:
•
Data 0 (bulk). Lowest priority queue, high throughput. Bulk data that requires maximum throughput
and is not time-sensitive is sent to this queue (FTP data, for example).
•
Data 1 (best effort). Medium priority queue, medium throughput and delay. Most traditional IP data is
sent to this queue.
•
Data 2 (interactive). Highest priority queue, minimum delay. Time-sensitive data such as VoIP and
streaming media are automatically sent to this queue.
•
Data 3 (not used)
Using the QoS settings on the VivatoVision UI, you can configure parameters that determine how each
queue is treated by the AP/Bridge.