Delta RMC101 - Manual (Page 367)

Ethernet 5.2
Communications 5-117
Finally, use the above frames/second results to compute the utilization by dividing the actual
bandwidth requirement by the maximum bandwidth and multiplying by 100%:
Utilization = 100% x actual bandwidth / maximum bandwidth
As noted above, the maximum bandwidths for 10 and 100 Mbps networks are 5,296 and 52,966
frames/second respectively.
Example:
Using the same setup as the previous example and assuming a switch is used, the utilization of the
six collisions domains are as follows:
RMC1-3/switch Utilization = 100% x 743 / 5,296 = 14.0%
RMC4/switch Utilization = 100% x 686 / 5,296 = 13.0%
The ControlLogix segments can run at either 10 or 100 Mbps (1756-ENBT only). If 10 Mbps is used,
then the utilization would be as follows:
CLX1/switch Utilization = 100% x 943 / 5,296 = 17.8%
CLX2/switch Utilization = 100% x 886 / 5,296 = 16.7%
If 100 Mbps is used, then the utilization would be as follows:
CLX1/switch Utilization = 100% x 943 / 52,966 = 1.8%
CLX2/switch Utilization = 100% x 886 / 52,966 = 1.7%
Again, if full-duplex is used with the 1756-ENBT, there will be no collisions in on the ControlLogix
collision domains.
Controlling Collisions
If you are experiencing or anticipate unacceptable levels of collisions, then you have several
options for reducing the number of collisions:
• Replace hubs with switches.
• Replace hubs and non-IGMP capable switches with IGMP capable switches.
• Replace half-duplex components with full-duplex components.
• Replace 10 Mbps with 100 Mbps components.
• Increase the RPI.
• Split the network into two or more smaller networks.
For further details, see Setting Up Large EtherNet/IP Networks.