Trango Systems TrangoLINK GigaPlus User Manual page 49

reduce or eliminate traffic loss in this case, buffers are used inside the IDU. These are
the same buffers used for QoS traffic grooming.
The traffic from all Ethernet ports share the buffers and are serially fed to the radio
section at a rate equal to or slightly less than the radio capacity. The egress margin
simply controls the egress rate in Mbps from the switch as a percentage added or
subtracted for the nominal link capacity. The default is 0% which means that the rate
from the switch into the modem section will be equal to the total link capacity. This
setting will provide the best throughput for all packet sizes, but may allow some high
priority packets to be dropped when the channel is overloaded (input rate > link
capacity).
By setting the egress margin to between -2 and -15 percent, the QoS will be enforced
and no high priority packets will be dropped. Also, the Egress margin may need to be
further reduced for strict QoS modes when datapath is set to Eth+t1 or Eth+E1 since the
actual channel capacity for Ethernet is reduced by roughly 12 or 16 Mbps , respectively.
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Trango Systems, Inc. GigaPlus User Manual Rev 3.1