參數(shù)資料
型號： MVTX2801AG
廠商： ZARLINK SEMICONDUCTOR INC
元件分類： 網(wǎng)絡(luò)接口
英文描述： Unmanaged 4-Port 1000 Mbps Ethernet Switch
中文描述： DATACOM, LAN SWITCHING CIRCUIT, PBGA596
封裝： 40 X 40 MM, 2.33 MM HEIGHT, MS-034, HSBGA-596
文件頁數(shù)： 22/106頁
文件大?。?/td> 1455K
代理商： MVTX2801AG
MVTX2801
Data Sheet
22
Zarlink Semiconductor Inc.
Figure 4 - Buffer Partition Scheme Used in the MVTX2801
7.8.1 Dropping When Buffers Are Scarce
Summarizing the two examples of local dropping discussed earlier in this chapter:
If a queue is a delay-bounded queue, we have a multilevel WRED drop scheme, designed to control delay
and partition bandwidth in case of congestion.
If a queue is a WFQ-scheduled queue, we have a multilevel WRED drop scheme, designed to prevent
congestion.
In addition to these reasons for dropping, the MVTX2801 also drops frames when global buffer space becomes
scarce. The function of buffer management is to ensure that such droppings cause as little blocking as possible.
7.9 Flow Control Basics
Because frame loss is unacceptable for some applications, the MVTX2801 provides a flow control option. When flow
control is enabled, scarcity of buffer space in the switch may trigger a flow control signal; this signal tells a source
port, sending a packet to this switch, to temporarily hold off.
While flow control offers the clear benefit of no packet loss, it also introduces a problem for quality of service. When
a source port receives an Ethernet flow control signal, all microflows originating at that port, well-behaved or not, are
halted. A single packet destined for a congested output can block other packets destined for uncongested outputs.
The resulting head-of-line blocking phenomenon means that quality of service cannot be assured with high
confidence when flow control is enabled.
In the MVTX2801, each source port can independently have flow control enabled or disabled. For flow control
enabled ports, by default all frames are treated as lowest priority during transmission scheduling. This is done so
that those frames are not exposed to the WRED Dropping scheme. Frames from flow control enabled ports 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 MVTX2801 does provide a system-wide option of permitting normal QoS scheduling (and buffer use) for frames
Shared Pool S
Temporary
Reservation R
TMP
Per-Class Reservations
R
p7
, R
p6
... R
p2
Per-Source Reservations 8 . R
1G
相關(guān)PDF資料
PDF描述
MVTX2802 Managed 4-Port 1000 Mbps Ethernet Switch
MVTX2802AG Managed 4-Port 1000 Mbps Ethernet Switch
MVTX2803 Unmanaged 8-Port 1000 Mbps Ethernet Switch
MVTX2803AG Unmanaged 8-Port 1000 Mbps Ethernet Switch
MVTX2804 8-Port 1000 Mbps Ethernet Distributed Switch
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MVTX2802 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Managed 4-Port 1000 Mbps Ethernet Switch
MVTX2802A 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Managed 4 port Gigabit Ethernet switch
MVTX2802AG 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Managed 4-Port 1000 Mbps Ethernet Switch
MVTX2803 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Unmanaged 8-Port 1000 Mbps Ethernet Switch
MVTX2803A 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Unmanaged 8 port Gigabit Ethernet switch
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