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參數資料
| 型號： | MVTX2804 |
| 廠商： | Zarlink Semiconductor Inc. |
| 英文描述： | 8-Port 1000 Mbps Ethernet Distributed Switch |
| 中文描述： | 8端口1000 Mbps以太網交換機分布式 |
| 文件頁數： | 34/174頁 |
| 文件大?。?/td> | 2249K |
| 代理商： | MVTX2804 |
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MVTX2804
Data Sheet
34
Zarlink Semiconductor Inc.
feed to only one queue at the destination, the queue of lowest priority. What this means is that if flow control is
enabled for a given source port, then we can guarantee that no packets originating from that port will be lost, but
at the possible expense of minimum bandwidth or maximum delay assurances. In addition, these “downgraded”
frames may only use the shared pool or the per-source reserved pool in the FDB; frames from flow control
enabled sources may not use reserved FDB slots for the highest six classes (P2-P7).
The MVTX2804 does provide a system-wide option of permitting normal QoS scheduling (and buffer use) for
frames originating from flow control enabled ports. When this programmable option is active, it is possible that
some packets may be dropped, even though flow control is on. The reason is that intelligent packet dropping is
a major component of the MVTX2804's approach to ensuring bounded delay and minimum bandwidth for high
priority flows.
7.9.1 Unicast Flow Control
For unicast frames, flow control is triggered by source port resource availability. Recall that the MVTX2804's
buffer management scheme allocates a reserved number of FDB slots for each source port. If a programmed
number of a source port's reserved FDB slots have been used, then flow control Xoff is triggered. Xon is
triggered when a port is currently being flow controlled, and all of that port's reserved FDB slots have been
released.
Note that the MVTX2804's per-source-port FDB reservations assure that a source port that sends a single
frame to a congested destination will not be flow controlled.
7.9.2 Multicast Flow Control
In unmanaged mode, a global buffer counter triggers flow control for multicast frames. When the system
exceeds a programmable threshold of multicast packets, Xoff is triggered. Xon is triggered when the system
returns below this threshold. MCC register programs the threshold.
In managed mode, per-VLAN flow control is used for multicast frames. In this case, flow control is triggered by
congestion at the destination. The MVTX2804 checks each destination to which a multicast packet is headed.
For each destination port, the occupancy of the lowest-priority transmission queue (measured in number of
frames) is compared against a programmable congestion threshold. If congestion is detected at even one of the
packet's destinations, then Xoff is triggered.
In addition, each source port has an 8-bit port map recording which port or ports of the multicast frame's fanout
were congested at the time Xoff was triggered. All ports are continuously monitored for congestion, and a port is
identified as uncongested when its queue occupancy falls below a fixed threshold. When all those ports that
were originally marked as congested in the port map have become uncongested, then Xon is triggered, and the
8-bit vector is reset to zero.
The MVTX2804 also provides the option of disabling multicast flow control.
Note
: If port flow control is on, QoS performance will be affected.
7.10 Mapping to IETF Diffserv Classes
The mapping between priority classes discussed in this chapter and elsewhere is shown below.
As the table illustrates, P7 is used solely for network management (NM) frames. P6 is used for expedited
forwarding service (EF). Classes P2 through P5 correspond to an assured forwarding (AF) group of size 4.
Finally, P0 and P1 are two best effort (BE) classes.
MVTX2804
P7
P6
P5
P4
P3
P2
P1
P0
IETF
NM
EF
AF0
AF1
AF2
AF3
BE0
BE1
Table 4 - Mapping between MVTX2804 and IETF Diffserv Classes for Gigabit Ports
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相關代理商/技術參數 |
參數描述 |
|---|---|
| MVTX2804AG | 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:8-Port 1000 Mbps Ethernet Distributed Switch |
| MVTX2804AG2 | 制造商:Microsemi Corporation 功能描述: |
| MVU10-10FBK | 功能描述:端子 D-10-1103K BS-33-10-P 85299 RoHS:否 制造商:AVX 產品:Junction Box - Wire to Wire 系列:9826 線規(guī):26-18 接線柱/接頭大小: 絕緣: 顏色:Red 型式:Female 觸點電鍍:Tin over Nickel 觸點材料:Beryllium Copper, Phosphor Bronze 端接類型:Crimp |
| MVU10-10FBX | 功能描述:端子 BLOCK FORK VNYL INS BTL BS-33-10-P RoHS:否 制造商:AVX 產品:Junction Box - Wire to Wire 系列:9826 線規(guī):26-18 接線柱/接頭大小: 絕緣: 顏色:Red 型式:Female 觸點電鍍:Tin over Nickel 觸點材料:Beryllium Copper, Phosphor Bronze 端接類型:Crimp |
| MVU10-10FBX-BOTTLE | 功能描述:CONN FORK BLOCK INSUL 50PC RoHS:是 類別:連接器，互連式 >> 端子 - 鏟形 系列:Scotchlok™ 標準包裝:1 系列:Scotchlok™ 端子類型:彈簧，壓接式 接線柱/接片尺寸:10 接線柱 寬度 - 外邊:0.320"（8.13mm） 長度 - 總體:1.030"（26.16mm） 安裝類型:自由懸掛 端子:壓接 線規(guī):10-12 AWG 絕緣體:絕緣 特點:- 顏色:黃 包裝:散裝 觸點表面涂層:錫 觸點材料:銅，ETP 絕緣體直徑:0.250"（6.35mm） 材料 - 絕緣體:聚酰胺（PA），尼龍 長度 - 環(huán)心道末端:0.280"（7.11mm） 長度 - 末端:0.550"（13.97mm） 內部舌簧打開:- 相關產品:TR-490-ND - HAND CRIMP TOOL RACHET 10-22 AWGTH-450-ND - TOOL HAND CRIMP 6-26AWGTR-482-ND - TOOL RATCHETING 10-22AWG CRIMP920099-R-ND - TOOL 10-22AWG SCOTCHLOK CRIMP 其它名稱:000511285879115112858791180611464373 |
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