Moxa Technologies PT-7728 user manual Using Traffic Prioritization, Traffic Prioritization Concept

PT-7728 User’s Manual Featured Functions

Port Status

Indicates the current Spanning Tree status of this port. Forwarding indicates normal transmission and Blocking indicates blocked transmission.

Configuration Limits of RSTP/STP

The Spanning Tree Algorithm places limits on three of the configuration items: [Eq. 1]: 1 sec ≦ Hello Time ≦ 10 sec

[Eq. 2]: 6 sec ≦ Max. Age ≦ 40 sec

[Eq. 3]: 4 sec ≦ Forwarding Delay ≦ 30 sec

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)

The PT-7728’s firmware will alert you immediately if any of these restrictions are violated. For example, suppose Hello Time = 5 sec, Max. Age = 20 sec, and Forwarding Delay = 4 sec. This does not violate Eqs. 1 through 3, but it violates Eq. 4:

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 seconds.

HINT: Take the following steps to avoid guessing:

Step 1: Assign a value to “Hello Time” and then calculate the left most part of Eq. 4 to get the lower limit of Max. Age.

Step 2: Assign a value to “Forwarding Delay” and then calculate the right most part of Eq. 4 to get the upper limit for Max. Age.

Step 3: Assign a value to Forwarding Delay that satisfies the conditions in Eq. 3 and Eq. 4.

Using Traffic Prioritization

The PT-7728’s traffic prioritization capability provides Quality of Service (QoS) to your network by making data delivery more reliable. 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. The PT-7728 can inspect both IEEE 802.1p/1Q layer 2 CoS tags, and even layer 3 TOS information to provide consistent classification of the entire network. The PT-7728’s QoS capability improves the performance and determinism of industrial networks for mission critical applications.

The Traffic Prioritization Concept

What is Traffic Prioritization?

Traffic prioritization 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:

yImprove network performance by controlling a wide variety of traffic and managing congestion.

yAssign priorities to different categories of traffic. For example, set higher priorities for time-critical or business-critical applications.

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