PRELIMINARY
Technical Description
Ethernet WAN Buffer
The WAN port buffer has been designed to handle burst and congestion in
order to provide a high link utilization and goodput for high-speed data traffic.
Since extensive buffering has a negative impact on frame delay variation, it is
important to have the possibility to configure buffer/queue size for different
traffic classes independently.
This means that queues configured to handle delay variation sensitive traffic
such as synchronization traffic, shall be configured to be very short.
In contrast, for traffic queues for less delay variation sensitive traffic the
Transmission Control Protocol/Internet Protocol (TCP/IP) has a congestion
avoidance mechanism that is based on buffer utilization. In order to provide a
high link utilization and high TCP goodput, queues configured to handle this
type of traffic needs to be in the area of hundreds of milliseconds at the smallest
congestion point, equivalent to the network end-to-end Round-Trip time.
LAN port buffers are designed to be very small in order to keep delay variation
as small as possible, whereas WAN port buffers are larger, to enable handling
of congestion at the WAN port. Congestion at the WAN port can occur when
the WAN port link speed is lower than the LAN port link speed.
4.2 Ethernet Capacity
The ethernet capacity depends on the configuration of the NE.
Table 2 Ethernet Capacity
ACM Profile
CS (MHz) ACM
Layer 1 Line Capacity (Mbps)
64 QAM
1000
32 QAM
1000
16 QAM
981
250
4 QAM
490
128 QAM
1000
64 QAM
1000
32 QAM
980
16 QAM
784
200
4 QAM
391
12 1/22102-HRA 901 17/9 Uen PU1 | 2016-07-04
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