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參數(shù)資料
| 型號： | MVTX1100 |
| 廠商： | Zarlink Semiconductor Inc. |
| 英文描述： | 9-Port Home PNA Packet Concentrator |
| 中文描述： | 9端口Home PNA的分組選礦廠 |
| 文件頁數(shù)： | 10/40頁 |
| 文件大小： | 435K |
| 代理商： | MVTX1100 |
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MVTX1100
Data Sheet
9
Zarlink Semiconductor Inc.
If the system uses the TOS/DS field to prioritize packets, there are two choices regarding which bits of the TOS/DS
field are used. Bits [0:2] of the TOS byte (known as the IP precedence field) or bits [3:5] of the TOS byte (known as
the DRT field) can be used to map the transmission queue priority. Either bits, [0:2] or [3:5], can also be used as a
packet drop precedence, by using bits 6 and 7 of the FCB Buffer Low Threshold register (FCBST).
MVTX1100 utilizes Weighted Round Robin (WRR) and Weighted Random Early Detection/Drop (WRED) to
schedule packets for transmission. To enable MVTX1100’s QoS capabilities requires the use of an external
EEPROM to change the default register configurations and turn on QoS.
Weighted Round Robin is an efficient method to ensure that each of the transmission queues gets at least a
minimum service level. With two output transmission queues, MVTX1100 will transmit “X” packets from the high
priority queue before transmitting “Y” packets from the low priority queue. MVTX1100 allows the designer to set the
high priority weight to a value between 0 and 16. The low priority weight is fixed at the value 1. If the high priority
weight is set to the value 4, then it will transmit 4 high priority packets before transmitting each low priority packet.
MVTX1100 also uses a proprietary mechanism to ensure the timely delivery of high priority packets. When the
latency of high priority packets reaches a threshold, it will override the WRR weights and transmit only high priority
packets until the high priority packet delays are below the threshold. This threshold limit is set at less than 1 ms
(last bit in and first bit out).
The QoS capabilities of the MVTX1100 are enabled by loading the appropriate values into the configuration
registers. QoS for packet transmission is enabled by performing the following four steps:
1. Select the TOS/DS or VLAN Priority Tag field as the control for IP packet transmission. The selection is made
using bit 7 of the Flooding Control (FCR[7]) register.
-
FCR[7]=0, use VLAN Priority Tag field to map the transmission priority if this Tag field exists.
-
FCR[7]=1, use TOS/DS field for IP packet transmission priority mapping.
2. Select which TOS/DS field to use as the control for packet transmission priority if the TOS/DS field was selected
in step 1. The selection is made using bit 6 of the FCB Buffer Low Threshold (FCBST[6]) register.
-
FCBST[6]=0, use DTR subfield to map the transmission priority.
FCBST[6]=1, use IP precedence subfield
1
to map the transmission priority.
-
3. Set the transmission queue weight for the high priority queue in the Transmission Scheduling Control
(AXSC[3:0]) register.
4. Set the priority mappings from the TOS/DS or VLAN Priority Tag field to the high or low priority output queue.
The selection is made using the VLAN Priority Map (AVPM) and TOS Priority Map (TOSPML) registers.
Note that, for half duplex operation, the priority queues
2
must be enabled using bit 7 in the Transmission
Scheduling Control (AXSC[7]) register to utilize the QoS function.
When QoS is enabled, MVTX1100 will utilize WRR to schedule packet transmission, and will use Weighted
Random Early Detection/Drop (WRED) to drop random packets in order to handle buffer memory congestion. In
this method, only certain packet flows are slowed down while the remaining see no impact from the network traffic
congestion.
Weighted Random Early Detection/Drop (WRED) is a method of handling traffic congestion in the absence of flow
control mechanisms. When flow control is enabled, all devices that are connected to a switch node that is
exercising flow control are effectively unable to transmit, including nodes that are not directly responsible for the
congestion problem. This inability to transmit during flow control periods would play havoc with voice packets, or
other high priority packet flows, and therefore flow control is not recommended for networks that mix voice and data
traffic.
1. IP precedence and DTR subfields are referred to as TOS/DS[0:2] and TOS/DS[3:5] in the IP TOS/DS byte.
2. In Half Duplex mode, the QoS functions are disabled by default.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MVTX2601 | Unmanaged 24-Port 10/100 Mbps Ethernet Switch |
| MVTX2601AG | Unmanaged 24-Port 10/100 Mbps Ethernet Switch |
| MVTX2602 | Managed 24 Port 10/100 Mbps Ethernet Switch |
| MVTX2602AG | Managed 24 Port 10/100 Mbps Ethernet Switch |
| MVTX2603 | Unmanaged 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 |
|---|---|
| MVTX1100AL | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Applications of the MDS108/MVTX1100 XLink Interface |
| MVTX2601 | 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Unmanaged 24-Port 10/100 Mbps Ethernet Switch |
| MVTX2601A | 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 Ethernet switch |
| MVTX2601AG | 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:Unmanaged 24-Port 10/100 Mbps Ethernet Switch |
| MVTX2601AG2 | 制造商:Microsemi Corporation 功能描述: |
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