Message Traverse Time is defined as the time required for a message to travel from its point of origin to its targeted destination over a network path. As the messages travels over the network path, it may pass through—and be forwarded by—a number of intermediate network devices, including switches and routers.
Message Traverse Time is impacted by several factors, including, for example, the following:
Message Traverse Time can be estimated by determining the transmission delay (the store and forward delay) of intermediate network devices and counting the number of such devices. Assuming each forwarding device is a switch, and each switch presents the same transmission delay, the following formula can be used:
Message Traverse Time =
(Switch Transmission Delay) x (Number of Switches)
Schneider Electric recommends that you estimate a worst-case Message Traverse Time, as follows:
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Step
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Description
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1
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Determine the worst case network load.
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2
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Obtain switch performance information, under varying network loads, and use the worst case—i.e., the largest—transmission delay value.
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3
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Determine the logical network topology that yields the longest path—i.e. the greatest number of switches—through which a message passes.
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4
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Using the largest transmission delay value and the largest number of forwarding switches, use the formula (above) to calculate a worst-cast Message Traverse Time.
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After calculating
Message Traverse Time (above), you can next measure
Message Response Time, which measures the total time required for:
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a message to travel from a client device over the network to a server
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the message to be processed by the server
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the server response to travel back to the client over the network
Message Response Time can be calculated as follows:
Message Response Time =
(2 x (Message Traverse Time)) + (Server Processing Time)
In the above formula, ‘2’ indicates a round trip required for client/server communication.
After Message Response Time is calculated, you can determine and configure the following parameters, both of which are found in the Channel Properties → EtherNet/IP page of the Control Expert Ethernet Configuration Tool:
