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參數(shù)資料
| 型號(hào)： | MVTX2602 |
| 廠商： | Zarlink Semiconductor Inc. |
| 英文描述： | Managed 24 Port 10/100 Mbps Ethernet Switch |
| 中文描述： | 管理的24端口10/100 Mbps以太網(wǎng)交換機(jī) |
| 文件頁(yè)數(shù)： | 34/147頁(yè) |
| 文件大?。?/td> | 924K |
| 代理商： | MVTX2602 |
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MVTX2602
Data Sheet
34
Zarlink Semiconductor Inc.
7.4 Strict Priority and Best Effort
When strict priority is part of the scheduling algorithm, if a queue has even one frame to transmit, it goes first. Two
of our four QoS configurations include strict priority queues. The goal is for strict priority classes to be used for IETF
expedited forwarding (EF), where performance guarantees are required. As we have indicated, it is important that
strict priority traffic be either policed or implicitly bounded, so as to keep from harming other traffic classes.
When best effort is part of the scheduling algorithm, a queue only receives bandwidth when none of the other
classes have any traffic to offer. Two of our four QoS configurations include best effort queues. The goal is for best
effort classes to be used for non-essential traffic because we provide no assurances about best effort performance.
However, in a typical network setting, much best effort traffic will indeed be transmitted and with an adequate
degree of expediency.
Because we do not provide any delay assurances for best effort traffic, we do not enforce latency by dropping best
effort traffic. Furthermore, because we assume that strict priority traffic is carefully controlled before entering the
MVTX2602, we do not enforce a fair bandwidth partition by dropping strict priority traffic. To summarize, dropping to
enforce bandwidth or delay does not apply to strict priority or best effort queues. We only drop frames from best
effort and strict priority queues when global buffer resources become scarce.
7.5 Weighted Fair Queuing
In some environments – for example, in an environment in which delay assurances are not required but precise
bandwidth partitioning on small time scales is essential, WFQ may be preferable to a delay-bounded scheduling
discipline. The MVTX2602 provides the user with a WFQ option with the understanding that delay assurances can
not be provided if the incoming traffic pattern is uncontrolled. The user sets four WFQ “weights” such that all
weights are whole numbers and sum to 64. This provides per-class bandwidth partitioning with error within 2%.
In WFQ mode, though we do not assure frame latency, the MVTX2602 still retains a set of dropping rules that helps
to prevent congestion and trigger higher level protocol end-to-end flow control.
As before, when strict priority is combined with WFQ, we do not have special dropping rules for the strict priority
queues, because the input traffic pattern is assumed to be carefully controlled at a prior stage. However, we do
indeed drop frames from SP queues for global buffer management purposes. In addition, queue P0 for a 10/100
port are treated as best effort from a dropping perspective, though they still are assured a percentage of bandwidth
from a WFQ scheduling perspective. What this means is that these particular queues are only affected by dropping
when the global buffer count becomes low.
7.6 Rate Control
The MVTX2602 provides a rate control function on its 10/100 ports. This rate control function applies to the
outgoing traffic aggregate on each 10/100 port. It provides a way of reducing the outgoing average rate below full
wire speed. Note that the rate control function does not shape or manipulate any particular traffic class.
Furthermore, though the average rate of the port can be controlled with this function, the peak rate will still be full
line rate.
Two principal parameters are used to control the average rate for a 10/100 port. A port’s rate is controlled by
allowing, on average, M bytes to be transmitted every N microseconds. Both of these values are programmable.
The user can program the number of bytes in 8-byte increments and the time may be set in units of 10 ms.
The value of M/N will, of course, equal the average data rate of the outgoing traffic aggregate on the given 10/100
port. Although there are many (M,N) pairs that will provide the same average data rate performance, the smaller the
time interval N, the "smoother" the output pattern will appear.
In addition to controlling the average data rate on a 10/100 port, the rate control function also manages the
maximum burst size at wire speed. The maximum burst size can be considered the memory of the rate control
mechanism; if the line has been idle for a long time, to what extent can the port "make up for lost time" by
transmitting a large burst This value is also programmable, measured in 8-byte increments.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MVTX2602AG | Managed 24 Port 10/100 Mbps Ethernet Switch |
| MVTX2603 | Unmanaged 24-Port 10/100 Mb + 2-Port 1 Gb Ethernet Switch |
| MVTX2603AG | Unmanaged 24-Port 10/100 Mb + 2-Port 1 Gb Ethernet Switch |
| MVTX2604 | Managed 24-Port 10/100 Mb + 2 Port 1 Gb Ethernet Switch |
| MVTX2604AG | Managed 24-Port 10/100 Mb + 2 Port 1 Gb Ethernet Switch |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MVTX2602A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:MVTX260x Port Mirroring |
| MVTX2602AG | 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Managed 24 Port 10/100 Mbps Ethernet Switch |
| MVTX2602AG2 | 制造商:Microsemi Corporation 功能描述: |
| MVTX2603 | 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Unmanaged 24-Port 10/100 Mb + 2-Port 1 Gb Ethernet Switch |
| MVTX2603A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Unmanaged 24 port 10/100Mb + 2 port 1Gb Ethernet switch |
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