Lync Edge Server - RSS configuration

One of the note on TechNet ( http://technet.microsoft.com/en-us/library/gg615015(v=ocs.15).aspx) recommends following

To improve the performance of the A/V Conferencing Edge service on your Edge Servers, you should enable receive-side scaling (RSS) on the network adapters on your Edge Servers. RSS enables incoming packets to be handled in parallel by multiple processors on the server. For details, see http://go.microsoft.com/fwlink/p/?LinkId=206013. For information on how to enable RSS, see your network adapter documentation.

1.1       RSS Configuration Parameters

In Windows Server 2008, the system default is for RSS to be enabled and to use a maximum of four CPUs. OEMs and administrators can adjust the maximum number of RSS processors by setting the MaxNumRssCpus registry value in HLKM\System\CurrentControlSet\Services\Ndis\Parameters. The value type is DWORD and if not present, the default value of four processors is assumed. Note that this value must not be set to value greater than 32.

In Windows Server 2008, an administrator can set the base CPU number that should be used for RSS. You can do this by setting the RssBaseCpu registry value in HLKM\System\CurrentControlSet\Services\NDIS\Parameters. The value type is DWORD and, if not present, a default value of 0 is assumed.

In Windows Server 2008, an administrator can determine the current state of RSS (enabled/disabled) in the operating system by executing the following command from an elevated command prompt:

C:\>netsh int tcp show global

Querying active state...

 

TCP Global Parameters

----------------------------------------------

Receive-Side Scaling State          : enabled

Chimney Offload State               : enabled

Receive Window Auto-Tuning Level    : highlyrestricted

Add-On Congestion Control Provider  : none

ECN Capability                      : disabled

RFC 1323 Timestamps                 : disabled

 

To enable or disable RSS, the following command can be used from an elevated command prompt:

E:\bin>netsh int tcp set global rss = enabled

Ok.

 

E:\bin>netsh int tcp set global rss = disabled

Ok.

 

These settings are global to the operating system and affect all network adapters in the system. An administrator can enable or disable RSS for a specific network adapter by navigating to the advanced properties for the NIC in device manager. Network adapters that support RSS have an entry in the advanced properties called “Receive-Side Scaling,” which can be enabled or disabled.