Latency tuning Step 4: Optimize the network and transport layers
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Optimizing the physical layer may include, but is not limited to, these recommendations:
n Use Ethernet switches instead of Ethernet hubs to minimize unnecessary traffic and minimize
collisions.
n Use industrial-strength cabling and ensure the wiring is sound. Bad wiring can result in
increased collisions.
n Eliminate impedance mismatches.
n Avoid running communications cabling on the same tracks with power cabling or other cabling
exhibiting fast voltage swings
n Use a smaller less noise-induced error-prone Ethernet or data rate. Lower Ethernet speeds
have higher voltages, where background noise is less relevant and has less impact on latency.
Voltages associated with 10, 100, and 1000 mbps Ethernet speeds are:
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 Use only networking equipment that is certified or known to operate well within the required
ranges for vibrations, shock, operating temperature, relative humidity.
Step 4: Optimize the network and transport layers
Depending on the results produced in steps 1, 2, and 3, optimize the network and transport layers.
Optimizing the network and transport layers, may include, but is not limited to, these
recommendations:
n Isolate any unnecessary TCP/IP traffic from the network.
n Choose smaller packets to reduce transit times through intermediate networking devices, as
most of these devices are store-and-forward.
n Increase the TCP/IP responsiveness to incoming/outgoing traffic by choosing appropriate
values for various TCP/IP timers, such as the retransmission timer, the gratuitous ARP timer,
the delayed acknowledgment timer, or by using the nodelay option in conjunction with TCP
sockets.
n Avoid using time-consuming encryption facilities.
Command options for optimizing network and transport layers
A major contributor to latency for the network and transport layers is unnecessary retransmissions of
data. The command-line interface has several command options to 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 TS Family Command Reference for
command descriptions.
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