Defined Architecture: Topologies
Original instructions
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Introduction
The defined architecture restricts the number of hops a packet takes from an RIO drop to the CPU. By restricting the number of hops, the application response time (ART) for the system can be calculated.
In any M580 network topology, the hop count is used as a factor in calculating network delay. To determine the hop count from the perspective of an RIO drop, count the number of switches from the remote drop to the CPU.
High Capacity Sub-System
The following is an example of a high capacity M580 system, consisting of a main ring, with multiple sub-rings: 
1
main ring 
2
RIO sub-ring 
3
DRSs connecting the main ring to the sub-rings 
4
CPU with Ethernet I/O scanner service on the local rack 
5
RIO drop with a BM•CRA312•0 X80 EIO adapter module
In this M580 network topology (with a single main ring and multiple sub-rings), these restrictions apply:
The maximum number of...
...is...
hops in a network path
17
RIO modules
16
devices in any sub-ring
16