We have a web server running Windows Server 2012 R@ and a SQL Server Analysis Server running Windows Server 2016. Both servers are virtualized machines in ESXi 6.5 Update 1. The web server is in our DMZ, the SQL server is in our LAN with connectivity through our Palo Alto firewall. We are getting intermittent errors when placing a load on the Analysis server running queries. The firewall shows no dropped packets. By default both operating systems have enabled the TCP enhancement of ECN. NIC settings in both have the default settings including TCP Chimney and various offloading.
A packet capture on an error shows apparent failure to negotiate the TCP session, I don't see any data transmitted.
web server sends SYN, ECN, CWR (indicates congestion) Window size value: 8192 [Calculated window size: 8192]
sql server sends with SYN, ACK, ECN Window size value: 8192 [Calculated window size: 8192]
web server sends ACK Window size value: 4106 [Calculated window size: 1051136] [Window size scaling factor: 256]
web server sends SYN, ACK, ECN Window size value: 8192 [Calculated window size: 8192]
sql server sends SYN, ACK, ECN Window size value: 8192 [Calculated window size: 8192]
web server sends ACK Window size value: 4106 [Calculated window size: 1051136] [Window size scaling factor: 256]
sql server sends RST, ACK Window size value: 0 [Calculated window size: 0] [Window size scaling factor: 256]
sql server sends RST, ACK Window size value: 0 [Calculated window size: 0] [Window size scaling factor: 256]
We've increased the timeouts in Analysis Server.
We've executed the following command on just one server, the SQL server, to turn off ECN and did not reboot: netsh int tcp set global ecncapability=disabled
The errors still occur. Can anyone give a clue as to what might be causing the issue? Thank you.
