Delta RMC101 User Manual
Page 366
RMC100 and RMCWin User Manual
5-116
Example (IGMP not supported by switch):
The ControlLogix/switch collision domains include all frames produced by any RMC on the
network. This was computed for the previous collision domain: 543 frames/second.
In addition to these frames, the ControlLogix/switch collision domains also include frames
produced by the ControlLogix and consumed by the RMCs. CLX1 produces frames for
RMC1, RMC2, and RMC3. CLX2 produces frames for RMC1, RMC2, and RMC4. Therefore,
the bandwidth for the CLX1/switch and CLX2/switch collision domains are as follows:
CLX1 Frames/Second = 543 + 2 / 0.010s + 1 / 0.005s = 943
CLX2 Frames/Second = 543 + 2 / 0.010s + 1 / 0.007s = 886
Notice that if a 1756-ENBT is used and full-duplex is used, then no collisions will occur. If
half-duplex is used, but 100 Mbps is used, then the utilization will be 1/10th that of 10 Mbps.
Example (IGMP supported by switch):
There are two ControlLogix/switch collision domains. Each sees frames produced for RMCs
by its ControlLogix and frames consumed by that ControlLogix. Therefore, this will be two
frames per RMC at each RPI:
CLX1 Frames/Second = 4 / 0.010s + 2 / 0.005s = 800
CLX2 Frames/Second = 4 / 0.010s + 2 / 0.007s = 686
• The collision domain for a network using a hub instead of a switch.
This collision domain will receive all frames consumed and produced by all RMCs.
Example:
This hub collision domain includes all frames. Therefore, we add the bandwidth required by
RMC-produced frames (543 frames/second) to the bandwidth required by all frames
consumed by RMCs:
Hub Frames/Second = 543 + 4 / 0.010s + 1 / 0.005s + 1 / 0.007s = 1,286
As stated above, utilization is a function of the available bandwidth (10 or 100 Mbps) and the
amount of data vying for the bandwidth. The amount of data includes the number and size of
frames being sent.
The available bandwidth for a 10 Mbps Ethernet network with 1,792-bit frames and the mandatory
96-bit inter-frame gap is 5,296 frames per second. The 1,792 number is the maximum frame size
used in an RMC I/O connection. The available bandwidth on a 100 Mbps Ethernet network is ten
times that of 10 Mbps, or 52,966 frames/second.