Latency tuning Achieving deterministicIPperformance
Digi Connect Family and ConnectPort TSFamily
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Achieving deterministic IP performance
Usethe following recommended processto achieve deterministic IPnetworking behavior. This
processuses Digi commercial off-the-shelf firmware and hardware, and doesnot use not any
specialized productsthat specifically reduce latency. By following this process, you can defineand
addresslatency issues at multiple levelsin your network and application. To achieve deterministic IP
networking behavior:
1. Determine the characteristics of your application, in termsof traffic pattern and amount of
traffic generated.
2. Determine the latency budget and the type of latency in which you are interested.
3. Depending on the resultsproduced in steps 1 and 2 and if applicable, optimize the physical
layer.
4. Depending on the resultsproduced in steps 1, 2, and 3 and if applicable, optimize the network
and transport layer.
5. Depending on the resultsproduced in steps 1, 2, 3, and 4and if applicable, optimize the
application layer.
Best-case scenario for achieving deterministic IP networking
behavior
Thebest-case scenario for achieving deterministic IPnetworking behavior with Digi firmware and
hardware is a unidirectional master-slaveapplication running over an isolated Ethernet network that
isbuilt around Ethernet switches instead of Ethernet hubs. In other words, a network that eliminates
unnecessary traffic and minimizesEthernet collisions.
Step 1: Determine the characteristics of your application
Consider your application in terms of traffic pattern and amount of traffic generated.
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What isthe main purposeof the application, and the primary activities?
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What isthe traffic pattern: Isit peer-to-peer or master-slave application?
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What isthe amount of traffic generated (x bytesevery y minutes): How much data is being
transmitted from and received by the application, and over what amount of time?For
example, 200 bytes of data sent over 500 milliseconds.
Step 2: Determine the latency budget and type of latency
Determine the latency budget and typeof latency in which you are interested. Identifying the latency
budget for your application involves defining what latency meansfor your network and the
application running on it. Consider how much latency isacceptable and whether the latency isone-
way or round-trip. Thislatency budget influences how much optimization you may need to perform at
the physical, data link/network, and application layers.
Step 3: Optimize the physical layer
Depending on the resultsproduced in steps 1 and 2, optimize the physical layer; that is, addressthe
physical-layer characteristicsthat can affect latency.
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