Low receive throughput when receive checksum offload is disabled and Receive Side Coalescing is enabled on Windows VM
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Low receive throughput when receive checksum offload is disabled and Receive Side Coalescing is enabled on Windows VM

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Article ID: 329062

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Updated On:

Products

VMware

Issue/Introduction

This is an adapter configuration issue at the OS level. This issue occurs if you have incorrect driver settings for receive checksum offload and RSC.

Note: RSC works as expected only when all of the receive checksum offloads  mentioned in the Symptoms section are Rx Enabled or  Rx & Tx Enabled.

Symptoms:
  • You notice low network receive throughput when receive checksum offload is disabled and Receive Side Coalescing (RSC) is enabled on Windows virtual machine.
  • The receive performance could be for example 2,400 times slower than usual, depending on environment.
  • It occurs when all of following conditions are met.
    • Guest operating system is Windows 2012 / Win 8 or later
    • Virtual machine hardware version is 11 or later
    • Virtual NIC driver is vmxnet3
    • RSC is enabled on the vmxnet3 driver on the guest operating system
    • Some or all of following receive checksum offloads have value Disabled or only Tx Enabled on the vmxnet3 driver on the guest operating system:
      • IPv4 Checksum Offload
      • TCP Checksum Offload (IPv4)
      • TCP Checksum Offload (IPv6)
      •  UDP Checksum Offload (IPv4)
      • UDP Checksum Offload (IPv6)


Cause

Poor file transfer speeds when RSC is enabled on the VMs

Resolution

This is a known issue affecting VMware ESXi 6.0, ESXi 6.5 and ESXi 6.7.

Windows VMwareTools 10.3.10 and later has a vmxnet3 driver with a feature for a restriction not to allow receive checksum offload to be disabled and RSC to be enabled.

Workaround:
To work around this issue, use one of these options: 
  • Disable RSC, if any of receive checksum offloads is disabled.
  • Manually enable receive checksum offloads using the following commands in Windows PowerShell:
Set-NetAdapterAdvancedProperty -DisplayName "IPv4 Checksum Offload" -DisplayValue "Rx & Tx Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "IPv4 TSO Offload" -DisplayValue "Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "Large Send offload v2 (ipv4)" -DisplayValue "Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "Large Send offload v2 (ipv6)" -DisplayValue "Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "TCP checksum offload (ipv4)" -DisplayValue "Rx & Tx Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "TCP checksum offload (ipv6)" -DisplayValue "Rx & Tx Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "UDP checksum offload (ipv4)" -DisplayValue "Rx & Tx Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "UDP checksum offload (ipv6)" -DisplayValue "Rx & Tx Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "Offload ip options" -DisplayValue "Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "Offload tcp options" -DisplayValue "Enabled"
Set-NetAdapterAdvancedProperty -DisplayName "Offload tagged traffic" -DisplayValue "Enabled"


Additional Information

https://osqa-ask.wireshark.org/questions/50123/win-2012-r2-vm-network-much-faster-after-wireshark-was-started

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