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參數資料
| 型號： | MVTX2603AG |
| 廠商： | ZARLINK SEMICONDUCTOR INC |
| 元件分類： | 網絡接口 |
| 英文描述： | Unmanaged 24-Port 10/100 Mb + 2-Port 1 Gb Ethernet Switch |
| 中文描述： | DATACOM, LAN SWITCHING CIRCUIT, PBGA553 |
| 封裝： | 37.50 X 37.50 MM, 2.33 MM HEIGHT, MS-034, HSBGA-553 |
| 文件頁數： | 29/109頁 |
| 文件大?。?/td> | 803K |
| 代理商： | MVTX2603AG |
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MVTX2603
Data Sheet
29
Zarlink Semiconductor Inc.
7.7 WRED Drop Threshold Management Support
To avoid congestion, the Weighted Random Early Detection (WRED) logic drops packets according to specified
parameters. The following table summarizes the behavior of the WRED logic.
Table 9 - WRED Drop Thresholds
Px is the total byte count, in the priority queue x. The WRED logic has three drop levels, depending on the value of
N, which is based on the number of bytes in the priority queues. If delay bound scheduling is used, N equals
P3*16+P2*4+P1. If using WFQ scheduling, N equals P3+P2+P1. Each drop level from one to three has defined
high-drop and low-drop percentages, which indicate the minimum and maximum percentages of the data that can
be discarded. The X, Y Z percent can be programmed by the register RDRC0, RDRC1. In Level 3, all packets are
dropped if the bytes in each priority queue exceed the threshold. Parameters A, B, C are the byte count thresholds
for each priority queue. They can be programmed by the QOS control register (refer to the register group 5).
7.8 Buffer Management
Because the number of FDB slots is a scarce resource and because we want to ensure that one misbehaving
source port or class cannot harm the performance of a well-behaved source port or class, we introduce the concept
of buffer management into the MVTX2603. Our buffer management scheme is designed to divide the total buffer
space into numerous reserved regions and one shared pool as shown in Figure 13 on page 30.
As shown in the figure, the FDB pool is divided into several parts. A reserved region for temporary frames stores
frames prior to receiving a switch response. Such a temporary region is necessary, because when the frame first
enters the MVTX2603, its destination port and class are as yet unknown and so the decision to drop or not needs to
be temporarily postponed. This ensures that every frame can be received first before subjecting them to the frame
drop discipline after classifying.
Six reserved sections, one for each of the first six priority classes, ensure a programmable number of FDB slots per
class. The lowest two classes do not receive any buffer reservation. Furthermore, even for 10/100 Mbps ports, a
frame is stored in the region of the FDB corresponding to its class. As we have indicated, the eight classes use only
four transmission scheduling queues for 10/100 Mbps ports, but as far as buffer usage is concerned, there are still
eight distinguishable classes.
Another segment of the FDB reserves space for each of the 26 ports ethernet port. Two parameters can be set, one
for the source port reservation for 10/100 Mbps ports, and one for the source port reservation for 1 Gbps ports.
These 26 reserved regions make sure that no well-behaved source port can be blocked by another misbehaving
source port.
In addition, there is a shared pool, which can store any type of frame. The frame engine allocates the frames first in
the six priority sections. When the priority section is full or the packet has priority 1 or 0, the frame is allocated in the
shared poll. Once the shared poll is full the frames are allocated in the section reserved for the source port.
相關PDF資料 |
PDF描述 |
|---|---|
| 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 |
| MVTX2801 | Unmanaged 4-Port 1000 Mbps Ethernet Switch |
| MVTX2801AG | Unmanaged 4-Port 1000 Mbps Ethernet Switch |
| MVTX2802 | Managed 4-Port 1000 Mbps Ethernet Switch |
相關代理商/技術參數 |
參數描述 |
|---|---|
| MVTX2603AG2 | 制造商:Microsemi Corporation 功能描述: |
| MVTX2604 | 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Managed 24-Port 10/100 Mb + 2 Port 1 Gb Ethernet Switch |
| MVTX2604A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:MVTX260x Physical Port Control |
| MVTX2604AG | 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Managed 24-Port 10/100 Mb + 2 Port 1 Gb Ethernet Switch |
| MVTX2801 | 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Unmanaged 4-Port 1000 Mbps Ethernet Switch |
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