troubleshooting Question

TCP Sliding Window and iSCSI

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amigan_99Flag for United States of America asked on
StorageNetworking ProtocolsCiscoTCP/IP
8 Comments3 Solutions198 ViewsLast Modified:
When you are running iSCSI, is TCP sliding window an important consideration? The situation is is Cisco UCS fabric interconnect to a Nexus 5k switch. The switch frequently drops packets inbound from the UCS and this appears to be an issue iSCSI frames from UCS being 1514 bytes which the interface on the Nexus is 1500 and jumbo framing is not enabled. I don't know why the vast majority of frames make it on through yet a significant number (in the millions) are dropped.
The port channel spikes up to about 10Gbps and most of that will be iSCSI. So the connection initiator to target works for the most part. I've planned to enable the jumbo frames as recommended by Cisco so that the 1514 iSCSI will be better processed and not dropped.

But my question is this: With iSCSI, are TCP conversations lengthy or very brief? To what degree would some dropped frames (.003%) in-path cause an issue for iSCSI TCP conversation? Or would this percentage just be noise that TCP connection orientedness should just deal with?
nociSoftware Engineer
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