Slow TCP connection

Question

I have a web server (Windows Server 2003 in a DMZ) that uses JDBC to connect to an Informix database (running on a Windows Server 2012 in the local network).

After migrating the web server to Windows Server 2012, the database connections are very slow. If I analyse the network traffic on the database server, that between an PSH,ACK packet and an ACK packet sent from the web server it elapses 0.5 sec (see my Wireshark log at the end). If I compare this to a log when I connect from the old web server, I don't see these 0.5 sec.

Can anybody help me find out if this 0.5 sec are needed by the database to query my SQL and answer. Or are these 0.5sec a delay from the network. If this looks like a network problem, do you have any tips for further tests? (By myself, I have no access to other network components between the web server and database server. I can only give rare information about the infrastructure and know nearly nothing about networks).

What I have tested so far:

• disable Windows Firewall on both servers
• disable IPv6 on the web server
• shutdown old web server and switch the IP of the new web server to the IP address of the old one
• disable Windows Autotuning on the web server (netsh interface tcp set global autotuning=disabled)

See my Wireshark log here: Wireshark log

Answer 1

In case anyone else face this problem. The delay of 0.5 sec appeared between every single TCP packet. After several tests we could eleminate this delay by switching the networkcards type of the web server (virtuel) from VMX0NET3 to E1000E in vSphere.