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EDS-518A Series User’s Manual Featured Functions
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2. As the 802.1p priority levels are fixed to the traffic queues, the packet will be placed in the
appropriate priority queue, ready for transmission through the appropriate egress port. When
the packet reaches the head of its queue and is about to be transmitted, the device determines
whether or not the egress port is tagged for that VLAN. If it is, then the new 802.1p tag is
used in the extended 802.1D header.
The EDS-518A will check a packet received at the ingress port for IEEE 802.1D traffic
classification, and then prioritize it based upon the IEEE 802.1p value (service levels) in that tag.
It is this 802.1p value that determines to which traffic queue the packet is mapped.
Traffic Queues
The EDS-518A hardware has multiple traffic queues that allow packet prioritization to occur.
Higher priority traffic can pass through the EDS-518A without being delayed by lower priority
traffic. As each packet arrives in the EDS-518A, it passes through any ingress processing (which
includes classification, marking/re-marking), and is then sorted into the appropriate queue. The
switch then forwards packets from each queue.
EDS-518A supports two different queuing mechanisms:
y Weight Fair: This method services all the traffic queues, giving priority to the higher priority
queues. Under most circumstances, this method gives high priority precedence over
low-priority, but in the event that high-priority traffic exceeds the link capacity, lower priority
traffic is not blocked.
y Strict: This method services high traffic queues first; low priority queues are delayed until no
more high priority data needs to be sent. This method always gives precedence to high priority
over low-priority.
Configuring Traffic Prioritization
Quality of Service (QoS) provides a traffic prioritization capability to ensure that important data is
delivered consistently and predictably. EDS-518A Series can inspect IEEE 802.1p/1Q layer 2 CoS
tags, and even layer 3 TOS information, to provide a consistent classification of the entire network.
EDS-518A Series’ QoS capability improves your industrial network’s performance and
determinism for mission critical applications.
QoS Classification
MOXA EDS-518A supports inspection of layer 3 TOS and/or layer 2 CoS tag information to
determine how to classify traffic packets.