Dell Networking S6000 Uživatelský manuál stáhnout pdf (Strana 284)

100

101

The following prerequisites and restrictions apply when you configure ETS bandwidth allocation or strict-

priority queuing in a DCB map:

• When allocating bandwidth or configuring strict-priority queuing for dot1p priorities in a priority group

on a DCBx CIN interface, take into account the CIN bandwidth allocation (see Configuring Bandwidth

Allocation for DCBx CIN) and dot1p-queue mapping.

• Although ETS bandwidth allocation or strict-priority queuing does not support weighted random early

detection (WRED), explicit congestion notification (ECN), rate shaping, and rate limiting because these

parameters are not negotiated by DCBx with peer devices, you can apply a QoS output policy with

WRED and/or rate shaping on a DCBx CIN-enabled interface. In this case, the WRED or rate shaping

configuration in the QoS output policy must take into account the bandwidth allocation or queue

scheduler configured in the DCB map.

Priority-Group Configuration Notes

When you configure priority groups in a DCB map:

• A priority group consists of 802.1p priority values that are grouped together for similar bandwidth

allocation and scheduling, and that share the same latency and loss requirements. All 802.1p priorities

mapped to the same queue must be in the same priority group.

• In a DCB map, each 802.1p priority must map to a priority group.

• The maximum number of priority groups supported in a DCB map on an interface is equal to the

number of data queues (4) on the port. Each priority group can support more than one data queue.

• You can enable PFC on a maximum of two priority queues on an interface.

• If you configure more than one priority group as strict priority, the higher numbered priority queue is

given preference when scheduling data traffic.

Priority-Based Flow Control Using Dynamic Buffer

Method

Priority-based flow control using dynamic buffer spaces is supported on the S6000 platform.

In a data center network, priority-based flow control (PFC) manages large bursts of one traffic type in

multiprotocol links so that it does not affect other traffic types and no frames are lost due to congestion.

When PFC detects congestion on a queue for a specified priority, it sends a pause frame for the 802.1p

priority traffic to the transmitting device.

Pause and Resume of Traffic

The pause message is used by the sending device to inform the receiving device about a congested,

heavily-loaded traffic state that has been identified. When the interface of a sending device transmits a

pause frame, the recipient acknowledges this frame by temporarily halting the transmission of data

packets. The sending device requests the recipient to restart the transmission of data traffic when the

congestion eases and reduces. The time period that is specified in the pause frame defines the duration

for which the flow of data packets is halted. When the time period elapses, the transmission restarts.

When a device sends a pause frame to another device, the time for which the sending of packets from

the other device must be stopped is contained in the pause frame. The device that sent the pause frame

empties the buffer to be less than the threshold value and restarts the acceptance of data packets.

284

Data Center Bridging (DCB)

1 2 ... 279 280 281 282 283 284 285 286 287 288 289 ... 985 986

Komentáře k této Příručce

Žádné komentáře

Dell Networking S6000 Uživatelský manuál Strana 284

Komentáře k této Příručce

Související produkty a manuály pro Software Dell Networking S6000