Latency tuning Step 4: Optimize thenetwork and transport layers
Digi Connect Family and ConnectPort TSFamily
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Optimizing the physical layer may include, but isnot limited to, these recommendations:
n
UseEthernet switchesinstead of Ethernet hubsto minimize unnecessary traffic and minimize
collisions.
n
Useindustrial-strength cabling and ensure the wiring is sound. Bad wiring can result in
increased collisions.
n
Eliminate impedance mismatches.
n
Avoid running communicationscabling on the same trackswith power cabling or other cabling
exhibiting fast voltage swings
n
Usea smaller less noise-induced error-prone Ethernet or data rate. Lower Ethernet speeds
have higher voltages, where background noise is lessrelevant and has lessimpact on latency.
Voltagesassociated with 10, 100, and 1000 mbpsEthernet speedsare:
l
10 mbps: 2.3V(CAT5)
l
100 mbps: 0.8V(CAT5)
l
1000 mbps: 0.5V(CAT5E/CAT6)
n
Ground to earth all your networking equipment, including the Digi device.
n
Useonly networking equipment that iscertified or known to operate well within therequired
rangesfor vibrations, shock, operating temperature, relative humidity.
Step 4: Optimize the network and transport layers
Depending on the resultsproduced in steps 1, 2, and 3, optimize the network and transport layers.
Optimizing the network and transport layers, may include, but isnot limited to, these
recommendations:
n
Isolate any unnecessary TCP/IPtraffic from the network.
n
Choose smaller packetsto reduce transit times through intermediate networking devices, as
most of these devicesare store-and-forward.
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Increase the TCP/IPresponsiveness to incoming/outgoing traffic by choosing appropriate
valuesfor variousTCP/IPtimers, such as the retransmission timer, the gratuitousARPtimer,
the delayed acknowledgment timer, or by using the nodelay option in conjunction with TCP
sockets.
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Avoid using time-consuming encryption facilities.
Command options for optimizing network and transport layers
Amajor contributor to latency for the network and transport layersisunnecessary retransmissionsof
data. The command-lineinterface has several command optionsto help you reduce these
unnecessary retransmissions. These options are available through the command-line interface only,
not the Web user interface. See the Digi Connect and ConnectPort TSFamily Command Reference for
command descriptions.
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