Transmitted Pause Frames

Network Switches

Network Switches
Information and ideas on Dell PowerConnect network switch solutions.

Transmitted Pause Frames

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Hi all, can anyone give me a little insight on "Transmitted Pause Frames"?  I am seeing this counter increment on my two 5448's on the two ports that take iSCSI traffic to one of my MD3000i SANs.  The weird part is that it is only happening when I do a hot backup of an Oracle database using Backup Exec's Oracle Agent.  All other backups and normal traffic to the same SAN do not cause this to increment.  I am getting lousy throughput on the backup, and also seeing a large percentage of dropped frames on the MD3000i during the same Oracle Backups. 

I put another post in the PowerVault forum, but noticed the Transmitted Pause Frames doing this, so I thought I would seek council here as well.  To the very best of my understanding, the MD3000i, the server NICs, and the PowerConnect switches are all set up in accordance w/ Dell's best practice docs.  Jumbo MTU on all devices, flow control on, pre-made CAT6 cabling, 1000 full, etc.

I haven't been able to find much on this particular counter.  I understand its meaning in principal I think...  Something somewhere is getting overwhelmed and slowing down traffic...  but haven't quite determined if it means that the switch is the origination point for the TPF's, or if the counter simply means that a TPF was passed through.

Many thanks!

All Replies
  • "Transmitted pause frames" means the switch is being over subscribed on one or more ports and is requesting that the sending devices stop sending it traffic for a short period of time.  pause frames are not passed through the switch.

    For a simple example consider: port 1 and port 2 each receiving 1G of traffic destined to be transmitted via port 3.  Port 3 can only transmit 1G of traffic, so port 3 buffers start to fill up, so the switch sends pause frames out port 1 and port 2 to request that the sending devices stop sending for a short time until port 3 can buffer up more traffic to be sent.

  • Same issue.. Any suggested fixes? I see no packets on this port inbound, so the explanation above doesn't make sense in my case.

  • I would start with making sure you have the most current firmware on the switch.  This is the maintenance release v2.0.0.46 for the Dell PowerConnect 54xx Ethernet switches:

    www.dell.com/.../DriverFileFormats

    Have you asked for assistance on our Storage Forum?

    en.community.dell.com/.../default.aspx

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