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Figure 13
Frame Discard Mechanisms
MINI-LINK PT 2010 supports a number of different frame discard mechanisms
for the TC/priority buffers. The different mechanisms are used in different
situations and are used for different purposes. In a live network, a combination
of different frame drop mechanisms is often used to get the required behavior.
Tail Drop
The tail drop discard mechanism is used when a TC buffer is filled up. When
a TC buffer is full, the tail drop feature ensures that new frames are dropped
at the entry point of the TC queue.
Tail drop is used to handle discarding of frames during long bursts that
completely fills up the available buffer space.
Time Stamp Based Dropping/Aging
A timestamp is applied to the frame when it enters the TC queue buffer. Before
exiting the TC buffer (that is, served by the scheduler) the timestamp is checked
towards the aging timer. If the timestamp value exceeds the aging timer, the
frame is discarded. The aging timer can be adjusted from the management
interface.
Aging is useful to discard frames in delay sensitive flows with expired delay
values and prevent further propagation of useless frames in the network.
Frame Discard Summary
Figure 14 illustrates how the different discard mechanisms are organized in
MINI-LINK PT 2010.
1/221 02-CSH 109 172/1-V1 Uen E | 2012-11-07
TC7: High prio
SP
SP
SP
SP
SP
SP
SP
TC0: Low prio
SP
Template 1
Scheduling Templates
MINI-LINK PT 2010 Functions – Ethernet
SP
SP
SP
SP
SP
SP
WFQ (40%)
WFQ (40%)
WFQ (30%)
WFQ (30%)
WFQ (15%)
WFQ (20%)
WFQ (10%)
WFQ (10%)
WFQ (5%)
SP
Template 2
Template 3
SP
SP
SP
SP
WFQ (50%)
WFQ (30%)
WFQ (20%)
SP
Template 4
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