Moxa Technologies EDS-405A User Manual download pdf (Page 57)

EDS-405A/408A Series User’s Manual Featured Functions

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Port Status

This indicates the current Spanning Tree status of this port. The status values are Forwarding for

normal transmission, and Blocking to block transmission.

Configuration Limits of RSTP/STP

The Spanning Tree Algorithm places limits on three of the configuration items previously

described:

[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 EDS’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 a multitude of ways. One solution is simply to increase the

Forwarding Delay to at least 11 sec.

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 DS’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 EDS can inspect

both IEEE 802.1p/1Q layer 2 QoS tags, and even layer 3 TOS information to provide consistent

classification of the entire network. The EDS’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:

y Improve network performance by controlling a wide variety of traffic and managing

congestion.

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Moxa Technologies EDS-405A User Manual Page 57