Contact Center Networking: Offload, Receive Side Scaling and Chimney
TCP/UDP/IP/Large Send/Large Receive/etc Offload tasks have been known to cause significant performance degradation as load increases on Windows 2003 and Windows 2008 servers running any Cisco Unified Contact Center software.
Cisco has released a number of field notices regarding these issues and steps to address the settings.
Here is the collated recommendations for Windows 2003 SP2 servers if they are part of a Contact Centre deployment.
NIC Device driver updated to latest version KB948496 downloaded and installed and server rebooted Disable RSS and TCP Offload in the network adapter driver, with these steps: Click Start, click Run, type ncpa.cpl, and then click OK. Right-click a network adapter object, and then click Properties. Click Configure, and then click the Advanced tab. In the Property list, click Receive Side Scaling, click Disable in the Value list, and then click OK. In the Property list, click TCP/IP Offload (IPv4 Checksum Offload), click Disable in the Value list, and then click OK. Repeat steps for Public and Private interfaces. Check the registry to confirm settings applied after KB patch
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters EnableTCPChimney = 0 EnableRSS = 0 EnableTCPA = 0
Add the following key in the registry to globally disable TCP Offload HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters New dword DisableTaskOffload = 1 Reboot the server again and check settings in TCP
These have shown to provide a significant improvment in buffering and latency issues across private network links.
For Windows 2008, please check the following link for TCP offload settings.