Getting network pause frames on G6 blade NICs.

[chuckk281]

Ramesh had a question on "Pause Frames" being seen on G6/G7 blades:

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Reaching out to experts to know if there is a known issue with pause frames on G6 blades.

I am aware that pause frames may occur on any G7 blade or any blade with NC55x Ethernet adapters but I am surprised to notice that most of the G6 blades on a VC domain experienced pause frames. VC domain consist of 3 enclosures, top enclosure bay1 VC module has Primary uplink, middle enclosure bay2 has Alternate uplink and bottom enclosure has backup uplink. NIC ports which are attached to bay1 module of middle enclosure were flapping and top enclosure & bottom enclosure lost connectivity to Alternate uplink. A quick look in to VCM reveals that ‘stacking links’ failed and alternate uplink at bay2 VC module of middle enclosure was not showing any connectivity (i.e. stacking links and uplink ports showing healthy but no remote device, mac, info)

Initially we thought it could be stacking cables issue but it turns out to be ‘pause frame’ issue. One of the blade in middle enclosure was generating too many frames. As soon as the blade was rebooted, everything reported back online (stacking links status ok, Alternate uplink online and no more flapping).

VC domain is on 3.70 firmware level and enclosures are at 3.56. I couldn’t find any article/advisory from HP which states that pause frames may occur on G6 blades.

Pause frames count:

Enc1:

D11

rfc2665_Dot3InPauseFrames                   598334

enc0

d1

rfc2665_Dot3InPauseFrames                   222188

d2

rfc2665_Dot3InPauseFrames                   114774

d3

rfc2665_Dot3InPauseFrames                   113476

d5

rfc2665_Dot3InPauseFrames                   116752

d6

rfc2665_Dot3InPauseFrames                   112090

d8

rfc2665_Dot3InPauseFrames                   108566

d9

rfc2665_Dot3InPauseFrames                   112166

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Reply from Chad:

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I think you are mistaken about Pause Frames occurring on a G7 blade or any NIC for that matter being a problem.

Pause frames are a normal part of Ethernet operations. 

Did you reset the counters and within a few seconds you had 100000+ Pause Frames? If these have not been reset or rebooted then this could be months of data.

100000 /(hypothetical)  500 Per Day = 200 Days which is only about 20 per hour. That is not much. Ant not nearly enough to fill up TX buffers

Excessive pause frames conditions means the driver/firmware has entered a condition where it is generating pause frames when it shouldn’t be. Those counters will be high and will rapidly increase.

Let’s make sure we are not telling HP customers they should not have pause frames. That is excessive pause frames.

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