Using Traffic Prioritization

EDS-508 Series User’s Manual

Featured Functions

These three variables are further restricted by the following two inequalities:

[Eq. 4]: 2 * (Hello Time + 1 sec) ≦ Max. Age ≦ 2 * (Forwarding Delay – 1 sec)

MOXA EtherDevice Switch’s firmware will alert you immediately if any of these restrictions are violated. For example, setting

Hello Time = 5 sec, Max. Age = 20 sec, and Forwarding Delay = 4 sec does not violate Eqs. 1 through 3, but does violate Eq. 4, since in this case,

2 * (Hello Time + 1 sec) = 12 sec, and 2 * (Forwarding Delay – 1 sec) = 6 sec.

You can remedy the situation in any number of ways. One solution is simply to increase the Forwarding Delay value to at least 11 sec.

Using the traffic prioritization capabilities of your EDS provides Quality of Service (QoS) to your network through increased reliability of data delivery. You can prioritize traffic on your network to ensure that high priority data is transmitted with minimum delay. Traffic can be controlled by a set of rules to obtain the required Quality of Service for your network. The rules define different types of traffic and specify how each type should be treated as it passes through the Switch. MOXA EtherDevice Switch can inspect both IEEE 802.1p/1Q layer 2 CoS tag, and even layer 3 TOS information to provide consistent classification of the entire network. MOXA EtherDevice Switch Series’ QoS capability improves the performance and determinism of industrial networks for mission critical applications.

The Concept of Traffic Prioritization

What is Traffic Prioritization?

Today’s application traffic consists of different types of data. When these different types of data compete for the same bandwidth, a network can quickly become overloaded, resulting in slow response times (long latency), and application time-outs. Traffic prioritization is a mechanism that allows you to prioritize data so that time-sensitive and system-critical data can be transferred smoothly and with minimal delay over a network. The benefits of using traffic prioritization are:

#You can control a wide variety of traffic and manage congestion on your network, therefore improving performance.

#You can assign priorities to traffic. For example, set higher priorities for time-critical or business-critical applications.

#You can provide predictable throughput for multimedia applications such as video conferencing or voice over IP, as well as minimize traffic delay and jitter.

#You can improve network performance as the amount of traffic grows, which also reduces the need to constantly add bandwidth to the network, therefore saving cost.

How Traffic Prioritization Works

Traffic prioritization uses the four traffic queues that are present in your EDS to ensure that high priority traffic is forwarded on a different queue from lower priority traffic. This is what provides Quality of Service (QoS) to your network.

EDS traffic prioritization depends on two industry-standard methods:

#IEEE 802.1D—a layer 2 marking scheme.

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