Module Utilization with RSNetWorx
For EtherNet/IP
EtherNet/IP Module Utilization using
RSNetWorx
A157730983
Current: June 9, 2006
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Module Utilization with RSNetWorx
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Purpose
This document describes how RSNetWorx for Ethernet can be used to provide Ethernet module
utilization. In a system of many controllers with I/O and produce/consume tags, the task of
calculating utilization of Ethernet modules is made simpler by using RSNetWorx.
Introduction
In any system, utilization of every Ethernet module is an important parameter. It is a measure of
how much CPU is in use (and how much is available).
RSNetWorx provides an easy way to calculate this utilization offline. RSNetWorx looks at the set
of connection originated by any connection originator device, including Logix.
For Logix, when running offline, RSNetworx is provided the connection information by
RSLogix5000. For Logix, when running online, RSNetWorx reads connection information from
connection originator devices.
Examples of connection originator devices are:
Logix controllers
Devices that indicate they support the Connection Configuration Object
o Indicated in the device EDS file
Module capacity information is specified in an EDS file (Electronic Data Storage).
The current version of RSNetWorx is 6. This version examines only I/O and produce/consume tag
information (packet rates and CIP connections).
One RSNetWorx file can be used by multiple RSLogix5000 files. For example:
I/O is being shared by 2 controllers
Multiple consumers of a produced tag
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Capacity Information
All EtherNet/IP interfaces, such as the 1756-ENBT module, provide capacity information. This
information allows utilization to be calculated for all modules in a system.
Using the 1756-ENBT module as an example, capacity information includes:
1. Connection Capacities
TCP
CIP
64
128
Includes I/O, HMI, and MSGing
2. Packet Rates Capacities (packets per second, PPS)
The ENBT module can handle HMI and I/O. Any combination of HMI or I/O cannot exceed
100% ENBT CPU utilization.
HMI (TCP)
900
This number represents 100% CPU utilization.
I/O (UDP)
5000* This number represents 80-100% CPU utilization.
NOTE that the 1756-ENBT module can run all HMI traffic or all I/O traffic or a combination but
cannot exceed 100% total for the combination of HMI and I/O.
Example:
Running 300 HMI packets/second (33% of 900) and 2500 I/O packets (50% of 5000)
would result in a total 1756-ENBT utilization of 83%.
3. Additional Capacities
I/O
32 end-nodes
16 controllers can have a rack connection to the module
16 controllers can have a rack-opt, listen-only to the module
32* multicast addresses
* The 1756-ENBT EDS file includes capacity information for several categories as marked above.
Other categories above are not included.
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Basic Steps to View EtherNet/IP Module Utilization
1. Use RSLogix000 to create a file with I/O
2. From RSLogix5000, launch RSNetWorx for Ethernet
A file RSNetWorx file name (.enet) is required.
3. In RSNetWorx, select an Ethernet interface and view Properties
Enable edits to see the device information.
4. In Properties, select the Device Usages tab.
That’s it!
The balance of this paper will provide a few screen-captures for the above 4 steps.
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Use RSLogix000 to create a file with I/O
The picture below shows I/O connections to a 1756-OB32 and another connection to a 1756-IB32
on EtherNet/IP.
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From RSLogix5000, launch RSNetWorx for Ethernet
To launch RSNetWorx from RSLogix5000, right-click on an ENBT module and select its
Properties page. Then will see number of tabs including a tab for RSNetWorx.
After entering a name for a new RSNetWorx file, select the Launch button to start RSNetWorx.
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RSNetWorx
When RSNetWorx first comes up, the network diagram will be blank.
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Select Enable Edits to see network
In the picture below, there are 3 chassis --- a controller chassis and 2 chassis with I/O.
Chassis 10.88.76.98 includes a Logix controller and ENBT module.
Chassis 10.88.76.96 includes an ENBT module and an output module.
Chassis 10.88.76.96 includes an ENBT module and an input module.
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Select Ethernet module
Hover the mouse over any of the modules to identify them – controller, Ethernet modules, I/O. In
the picture below, a 1756-ENBT was selected.
Right-click and select Properties to see the picture below. (Be careful not to select the chassis)
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Select Device Usage Tab
All information on this tag is based on I/O capacity information in the module EDS file.
If capacity information is missing from the EDS file, usage is not calculated.
CPU Usage (relates to I/O or produce/consume packets per second)
Minimum: All I/O is calculated as being sent and received at the RPI rates.
Using the RPIs, RSNetWorx calculates the I/O packet rate (packets/second),
and then divides by the packet capacity from the EDS file.
In the above screen 2 Rack connections were included. One at RPI=10ms and the
other at RPI = 20ms. The total I/O packet rate was 300 packets per second. This
is 6% (300/5000) CPU for the packet rate.
Maximum: Periodic or change-of-state (COS)
Data can be configured for COS or periodic data production. In the example
above, data is configured to produce periodically (cyclic, using the RPI).
All change-of-state (COS) I/O is considered running at the production-inhibit rate.
Any connections configured for COS will be calculated as running at the
production-inhibit rate. Production inhibit only applies to change-of-state
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connections. The sum of cyclic and COS connections will provide maximum
packet usage.
Typically, the production-inhibit rate is 4 times the RPI value.
Example: If the RPI is 20ms, the ENBT module will not send data faster than 5ms
(20ms/4).
Connection Usage
The number of CIP connections in use, divided by the CIP connection capacity.
In the above example, the 2 I/O connections were 1.56% of the 128 ENBT CIP
connections.
Consume Usage and Produce Usage
These statistics have no data because the 1756-ENBT module has a pool of
connection information that does not, in the EDS file, differentiate between I/O
and produce/consume usage. In the screen capture above, only I/O connections
were used. In the screen capture below, for produce/consume the consume usage
produce usage are still empty because, as stated, the 1756-ENBT does not
differentiate between types of connections.
Bytes Per Second
Minimum: If all I/O is being sent/received at the RPI rates.
Maximum: If some or all I/O is configured for COS, those connections are calculated as
running at the production inhibit rate.
When RSLogix5000 writes connection information in the .enet file, it includes the number
of bytes of application data. This is also true when connection information is obtained
online from a Logix controller or a Connection Configuration Object.
Packets Per Second
Minimum: If all I/O is being sent/received at the RPI rates.
Maximum: If some or all I/O is configured for COS, those connections are calculated as
running at the production inhibit rate.
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Produce/consume Tag
Another RSLogix5000 file was generated to demonstrate produce/consume tag.
In the picture below, the tag producer is at IP address 1.2.3.5.
Also, the two tag consumers are at IP addresses 1.2.3.4 and 1.2.3.6.
The RPI was 5ms for both consumed tags.
Notice that the Ethernet module with the worst-case usage is shown below to be module 1.2.3.5.
The packet rate utilization is shown as 12%.
The connection utilization is shown to be 1.56%.
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The tag producer is at IP address 1.2.3.5. Examining the producer controller:
The calculated ENBT packet usage is (1 + 2))/.005 = 600 PPS, which is 12%.
The calculated ENBT CIP connection usage is 2/128 which is 1.56%.
Below, RSNetWorx usage values agree with the calculated values.
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Examining either of the two consumers:
the calculated ENBT packet usage is 2/.005 = 400 PPS, which is 8%.
the calculated ENBT CIP connection usage for each consumer is 1/128, which is 0.78%.
Below, RSNetWorx usage values agree with the calculated values.
End of document…
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