Indu-Sol PROmesh P20, Руководство пользователя

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PROmesh P20 - User Manual 46
Figure 25: Quality of Service
QoS mode and priority scheme
Within the QoS mode, a differentiation is made between the following settings:

Port-based only : You can specify a priority for the data transmission for each port. The switch
forwards the data packages of the respective port according to their priority. You can configure
settings for this type of QoS in the Port Configuration submenu.

Class of Service only : COS uses a data field with priority information existing in the VLAN Tag.
Eight different priority values are specified here, from Best Effort (BE,0-low) to Network Control
(NC,7-high). Assign the COS priorities to the four queues of the switch as you need it in your
application.

Type of Service only : TOS uses the data field Differentiated Services Code Point (DSCP) in the
IP header of the packages, which can have up to 64 different priorities. As with COS, these priorities
can be used to prioritise real-time control data, Voice over IP (VoIP) or audio data over normal data
transmission. Adapt the settings according to your requirements. To do so, select the desired DSCP
priority and assign it to a CoS priority.
Selection priority mode:

Strict Priority Scheme (SP) : In the strict priority scheme, all packages leave a port until the
corresponding priority queue is empty. Only then are packages sent from the queues with lesser
priority. If packages are permanently arriving in the queue with the highest priority, it may be that
package with the lowest queue are never sent. This mode is recommended if there really strong
real-time requirements.

Weighted fair queueing : This approach ensures that not only high-priority packages but also
packages with lesser priority are sent. This is made possible by sending packages of a queue
based on a customizable weighting. Once all queues have been processed, the cycle restarts. This
leads to only minor increased latency for the high-priority packages. To configure the weighting,