zl50417 ETC-unknow, zl50417 Datasheet - Page 29

• Manufacturer Part Number: zl50417
• Description: Unmanaged 16-port 10/100m +2-port Ethernet Switch
• Manufacturer: ETC-unknow

Data Sheet
Best-effort (P0) traffic forms a fourth class that only receives bandwidth when none of the other classes have any
traffic to offer. It is also possible to add a fourth class that has strict priority over the other three; if this class has
even one frame to transmit, then it goes first. In the ZL50417, each 10/100 Mbps port will support four total classes,
and each 1000 Mbps port will support eight classes. We will discuss the various modes of scheduling these classes
in the next section.
In addition, each transmission class has two subclasses, high-drop and low-drop. Well-behaved users should rarely
lose packets. But poorly behaved users – users who send frames 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, and then all frames in the worst case.
Table 6 shows that different types of applications may be placed in different boxes in the traffic table. For example,
casual web browsing fits into the category of high-loss, high-latency-tolerant traffic, whereas VoIP fits into the
category of low-loss, low-latency traffic.
7.2
There are four basic pieces to QoS scheduling in the ZL50417: strict priority (SP), delay bound, weighted fair
queuing (WFQ), and best effort (BE). Using these four pieces, there are four different modes of operation, as shown
in the tables below. For 10/100 Mbps ports, the following registers select these modes:
QOSC40 [7:6] and QOSC48 [7:6] select these modes for the first and second gigabit ports, respectively.
Four QoS Configurations
Op1 (default)
Op2
Op3
Op4
Op1 (default)
Op2
Op3
Op4
Table 4 - Four QoS Configurations for a 10/100 Mbps Port
Delay Bound
SP
SP
WFQ
Delay Bound
SP
SP
WFQ
Table 5 - Four QoS Configurations for a Gigabit Port
P7
QOSC24 [7:6]_CREDIT_C00
QOSC28 [7:6]_CREDIT_C10
QOSC32 [7:6]_CREDIT_C20
QOSC36 [7:6]_CREDIT_C30
P3
P6
Zarlink Semiconductor Inc.
Delay Bound
WFQ
Delay Bound
WFQ
P5
P2
P4
P3
P1
P2
BE
BE
BE
BE
P1
P0
ZL50417
P0
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