IE-SW-VL08M Series User’s Manual
Featured Functions
3-41
[Eq. 4]: 2 * (Hello Time + 1 sec)
≦
Max. Age
≦
2 * (Forwarding Delay – 1 sec)
The 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 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 device 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 switch’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.
y
Assign priorities to different categories of traffic. For example, set higher priorities for
time-critical or business-critical applications.
y
Provide predictable throughput for multimedia applications, such as video conferencing or
voice over IP, and minimize traffic delay and jitter.
y
Improve network performance as the amount of traffic grows. This will save cost by reducing
the need to keep adding bandwidth to the network.
How Traffic Prioritization Works
Traffic prioritization uses the four traffic queues that are present in your device 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.
The switch traffic prioritization depends on two industry-standard methods:
