MVTX2803 查看數據表（PDF） - Zarlink Semiconductor Inc
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MVTX2803 Datasheet PDF : 127 Pages
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MVTX2803
Data Sheet
Class
Example
Assured Bandwidth
(user defined)
Low Drop Subclass
(If class is oversubscribed,
these packets are the last to
be dropped)
High Drop Subclass
(If class is oversubscribed,
these packets are the first
to be dropped)
Highest transmission
priorities, P6
Latency < 200 µs
Middle transmission
priorities, P5
Latency < 400 µs
Middle transmission
priorities, P4
Latency < 800 µs
Low transmission
priorities, P3
Latency < 1600 µs
Low transmission
priorities, P2
Latency < 3200 µs
Best effort, P1-P0
TOTAL
200 Mbps
Sample applications: phone Sample application: training
calls; circuit emulation
video; other multimedia
125 Mbps
250 Mbps
Sample application:
interactive activities
Sample application: web
business
Sample application:
non-critical interactive
activities
80 Mbps
Sample application: file
backups
45 Mbps
Sample application: email
Sample application: web
research
–
Sample application: casual web browsing
1 Gbps
Table 1 - Two-dimensional World Traffic (continued)
It is possible that a class of traffic may attempt to monopolize system resources by sending data at a rate in
excess of the contractually assured bandwidth for that class. A well-behaved class offers traffic at a rate no
greater than the agreed-upon rate. By contrast, a misbehaving class offers traffic that exceeds the agreed rate.
A misbehaving class is formed from an aggregation of misbehaving microflows. To achieve high link utilization,
a misbehaving class is allowed to use any idle bandwidth. However, the quality of service (QoS) received by
well-behaved classes must never suffer.
As Table 1 illustrates, each traffic class may have its own distinct properties and applications. As shown,
classes may receive bandwidth assurances or latency bounds. In the example, P7, the highest transmission
class, requires that all frames be transmitted within 0.2 ms, and receives 30% of the 1 Gbps of bandwidth at that
port.
Best-effort (P1-P0) traffic forms a lower tier of service that only receives bandwidth when none of the other
classes have any traffic to offer.
In addition, each transmission class has two subclasses, high-drop and low-drop. Well-behaved users should
not lose packets. But poorly behaved users – users who send data at too high a rate – will encounter frame
loss, and the first to be discarded will be high-drop. Of course, if this is insufficient to resolve the congestion,
eventually some low-drop frames are dropped as well.
Table 1 shows that different types of applications may be placed in different boxes in the traffic table. For
example, web search may fit into the category of high-loss, high-latency-tolerant traffic, whereas VoIP fits into
the category of low-loss, low-latency traffic.
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