Egress Margin Setting

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    Brian Maletsky

    What does the value of – translate into % it will take off of total capacity through the radio. Also is a reboot required to apply the settings?

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    Scott Chester

    The integer that is entered is set as a % of the expected RF throughput based on larger packet sizes. You'll see in the data above that it doesn't really change the throughput significantly for larger packets when going up, but that this impacts how much space is reserved by the QoS engine. If enough space is saved for a 1518 bye packet and only a 64 byte packet ends up using the saved space, the overall throughput ends up reduced slightly.

    Setting a negative number will restrict the throughput. I.e if the expected throughput based on a 30 MHz channel and qam32 modulation is 118 Mbps and you set the egress margin to -10% the expected maximum throughput would be 118 Mbps RF rate, - 10% of 118 Mbps or 12 Mbps, yielding 106 Mbps. This would commonly not be used which is why the article above discusses using 5-20% as this is most typical.

    A reboot is not required for the setting to be programmed, it can be changed live.

    Note: While the article mentions a default setting of 10%, if you upgrade from a previous version the value will likely not be set and one must enter 10% into the egress margin field.

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