The 1756-ENBT has a total bandwidth of 5000 frames/second. If we reserve 10% of this bandwidth for non-I/O communications (RSLogix 5000, etc.), then we are left with 4500 frames/second. This is enough bandwidth to control eleven RMCs at the RMCs' minimum RPI of 5 ms. As will be discussed in the next topic, collisions on the RMC-to-switch collision domains preclude this many RMCs being placed on the same network with such a low RPI in most applications.
The load on the 1756-ENBT is computed in the same way as the 1756-ENET. However, for the purpose of controlling RMCs, the collisions will be the limiting factor in network performance and determinism when using a 1756-ENBT. See Predicting the Effect of Collisions for details. For additional considerations when setting up large EtherNet/IP networks, see Setting Up Large EtherNet/IP Networks.
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