User`s manual

EDS-516A Series User’s Manual Featured Functions
3-34
Port Cost
Setting Description Factory Default
Numerical value input by
user
Input a higher cost to indicate that this port is
less suitable as a node for the Spanning Tree
topology.
200000
Port Status
Indicates the current Spanning Tree status of this port. “Forwarding” for normal transmission, or
“Blocking” to block transmission.
Configuration Limits of RSTP/STP
The Spanning Tree Algorithm places limits on three of the configuration items described
previously:
[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-516A’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 many ways. One solution is simply to increase the Forwarding
Delay value to at least 11 sec.
HINT: Perform 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 EDS-516A’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-516A 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 EDS-516A’s QoS capability
improves the performance and determinism of industrial networks for mission critical applications.