User Manual

Moxa’s Managed Switch Next Generation OS (v3.x) User Manual
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Traffic Prioritization
Moxa switches classify traffic based on layer 2 of the OSI 7 layer model, and the switch prioritizes outbound
traffic according to the priority information defined in the received packet. Incoming traffic is classified
based upon the IEEE 802.1p service level field and is assigned to the appropriate egress priority queue. The
traffic flow through the switch is as follows:
• A packet received by the Moxa switch may or may not have an 802.1p tag associated with it. If it does
not, then it is given a default CoS value (according to the port settings in the classification section).
Alternatively, the packet might be marked with a new 802.1p value, which will result in all knowledge of
the previous 802.1p tag being lost.
• Each egress queue has associated 802.1p priority levels, and can be defined by users, the packet will be
placed in the appropriate priority queue. When the packet reaches the head of its queue and is about to
be transmitted, the device determines whether or not the egress port belongs to the VLAN group. If it
is, then the new 802.1p tag is used in the extended 802.1D header.
Traffic Queues
The hardware of Moxa switches has multiple traffic queues that allow packet prioritization to occur. Higher
priority traffic can pass through the Moxa switch without being delayed by lower priority traffic. As each
packet arrives in the Moxa switch, it undergoes ingress processing (which includes classification,
marking/re-marking), and is then sorted into the appropriate queue. The switch then forwards packets from
each queue.
Moxa switches support two different queuing mechanisms:
• Weight Fair: This method services all the traffic queues, giving priority to the higher priority queues.
Under most circumstances, the Weight Fair method gives high priority precedence over low priority, but
in the event that high priority traffic does not reach the link capacity, lower priority traffic is not
blocked.
• Strict: This method services high traffic queues first; low priority queues are delayed until no more high
priority data needs to be sent. The Strict method always gives precedence to high priority over low
priority.
Classification
There are three parameters in this section: DSCP Mapping, CoS Mapping, and Port Setting. The three
parameters are described below in detail.
DSCP to CoS Mapping
In the Classification menu, click the DSCP Mapping tab, and then click the edit icon.