Cisco Nexus 5K's Tx Pause Frames with no Rx frames

[victor.rosa]

We have an EMC SAN connected via 10G links on a 5010. At some times we have iSCSI disconnects generated by the SAN.

We are seeing Tx pause frame, but no Rx frames. No packet loss, no errors. The "normal" utilization is around 23Mbit.

Under what conditions might this happen?

[tiwang]

hi Victor

I cannot answer your question but confirm what you are seeing. As far as I am aware of these Tx pause frames are send from the SP when it cannot catch up with switch. If you will re-act on the pause frames you have to activate flow-control on that particular interface. I would expect that the iSCSI protocol handles the session so that it doesn't loose any packets

It is local control packets between the SP's I/F and the Nexus I/F and the nexus hasn't got much buffering to pace a flow with.

We are seeing this behavior between nx5010 switches and EMC VNX5500 SAN. I don't think your disconnects have any thing to do with the pause frames.

best regards /ti