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Why does flow-control sometimes not engage properly on a Dell™ PowerConnect™ 3024 or 5012 switch? - Technical Tip - 166086

Why does flow-control sometimes not engage properly on a Dell™ PowerConnect™ 3024 or 5012 switch?

Turn off the High-Priority Traffic Optimization option. The High-Priority Traffic Optimization should only be enabled in scenarios where the default switch settings result in a unacceptably high latency for high-priority traffic.

For additional information on disabling the High-Priority Traffic Optimization option, refer to the User's Guide for your specific Dell PowerConnect switch:

When the High-Priority Traffic Optimization option is enabled, flow-control is not engaging for ports that are receiving packets with normal priority.

With High-Priority Traffic Optimization, an advanced priority-based head-of-line blocking prevention algorithm is being used. This algorithm will drop normal priority packets in the ingress queue if they cannot be sent to the egress queue of the destination port, due to over-subscription. This internal dropping of normal priority packets ensures that no high-priority packets are being held-up in the switch. Due to the internal dropping of packets, flow control will not engage on the ingress port for normal priority packets.

NOTE: This does not affect ports that receive high-priority packets.


Quick Tips content is self-published by the Dell Support Professionals who resolve issues daily. In order to achieve a speedy publication, Quick Tips may represent only partial solutions or work-arounds that are still in development or pending further proof of successfully resolving an issue. As such Quick Tips have not been reviewed, validated or approved by Dell and should be used with appropriate caution. Dell shall not be liable for any loss, including but not limited to loss of data, loss of profit or loss of revenue, which customers may incur by following any procedure or advice set out in the Quick Tips.

Article ID: SLN49133

Last Date Modified: 11/14/2010 12:00 AM

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