Comtech EF Data CDM-570/L Vipersat Parameter Editor - Manual (Page 32)

Network
2-16 CDM-570/L, CDD-56X Parameter Editor User Guide
Figure 2-12 Protocol Drop-Down Menu
Priority
This field is active for Rule Max/Priority mode only.
A Priority level from 1 (highest) to 9 (lowest) is assigned for each flow using
the Priority field. The modem/router classifies each packet that is to be
forwarded over the satellite using the priority assigned for the selected Protocol.
Any packet that does not meet a QoS Rule is assigned to the Default Rule and
will be assigned a Priority of 9. Priority 1 packets will be forwarded immedi-
ately, Priority 2 packets will be forwarded as soon as there are no priority 1
packets in the queue, and so on. Any latency-critical traffic, such as VoIP/RTP
should always be assigned Priority 1.
Enable WRED
Selecting the Enable WRED (Weighted Random Early Detection) check box in
the dialog shown in figure 2-11 enables this function in the modem/router.
WRED allows for more graceful dropping of packets, as QoS queues get full.
Without WRED, output buffers fill during periods of congestion. When the
buffers are full, all additional packets are dropped. Typically, packets are
dropped based upon a simple tail drop algorithm applied to packets as they were
being added to the QoS queues. This can result in large numbers of contiguous
packets being dropped all at once, which causes many protocols such as RTP
and TCP to ungracefully degrade performance in an over-consumed or bursty
scenario.
WRED applies a randomization, which means that the percentage change to
dropped packets increases as the queue becomes full, and minimizes the