PowerShell: Windows Server – Tune the TCP Stack for 10GbE Workloads

.\Optimize-TcpStackFor10GbE.ps1 -AdapterName "SLOT 2 Port 1"

.\Optimize-TcpStackFor10GbE.ps1 -AdapterName "SLOT 2 Port 1", "SLOT 2 Port 2" -RssBaseProcessorNumber 2 -RssMaxProcessors 8 -EnableJumboFrame

.\Optimize-TcpStackFor10GbE.ps1 -AdapterName "SLOT 2 Port 1" -NoRestart
Restart-NetAdapter -Name "SLOT 2 Port 1"

WARNING: Legacy value TcpWindowSize is set under Tcpip\Parameters. Windows ignores it; remove it to avoid confusion.
WARNING: TCP Chimney global state is 'Enabled'. Chimney is deprecated; see Notes before changing it.

Name          Enabled Profile    BaseProcessorNumber MaxProcessors NumberOfReceiveQueues
----          ------- -------    ------------------- ------------- ---------------------
SLOT 2 Port 1    True NUMAStatic                   2             8                     8
SLOT 2 Port 2    True NUMAStatic                   2             8                     8

Name          IPv4Enabled IPv4OperationalState IPv4FailureReason
----          ----------- -------------------- -----------------
SLOT 2 Port 1        True                 True NoFailure
SLOT 2 Port 2        True                 True NoFailure

Name          JumboPacket
----          -----------
SLOT 2 Port 1 9014
SLOT 2 Port 2 9014

SettingName AutoTuningLevelLocal CongestionProvider
----------- -------------------- ------------------
Datacenter  Normal               CUBIC
Internet    Normal               CUBIC

ping.exe -f -l 8972 <storage-target-ip>

<#
.SYNOPSIS
    Audits and tunes NIC offloads and TCP autotuning on Windows Server for 10GbE (or faster) adapters.
.DESCRIPTION
    Enables Receive Side Scaling (optionally setting the base processor and
    processor cap), Receive Segment Coalescing, checksum offload and Large Send
    Offload on the named adapters, optionally sets the *JumboPacket keyword, and
    makes sure TCP receive window autotuning is at its default, Normal. Reports,
    without changing, the TCP Chimney global state and any legacy Tcpip registry
    values that Windows ignores. Prints a summary of the resulting settings.
.PARAMETER AdapterName
    One or more network adapter names, as shown by Get-NetAdapter.
.PARAMETER RssMaxProcessors
    Maximum number of processors RSS may use per adapter. Only changed when supplied.
.PARAMETER RssBaseProcessorNumber
    First processor number RSS may use. Only changed when supplied.
.PARAMETER EnableJumboFrame
    Sets the *JumboPacket keyword to JumboPacketSize, if the adapter exposes it.
.PARAMETER JumboPacketSize
    Frame size in bytes including the Ethernet header. Default 9014.
.PARAMETER NoRestart
    Passes -NoRestart to the adapter cmdlets; changes apply at the next adapter restart.
.EXAMPLE
    .\Optimize-TcpStackFor10GbE.ps1 -AdapterName "SLOT 2 Port 1", "SLOT 2 Port 2" -RssBaseProcessorNumber 2 -RssMaxProcessors 8 -EnableJumboFrame
.NOTES
    Author  : Thomas Lasswell (https://www.techcolumnist.com)
    Version : 1.0 (2025-04-10)
    Requires: Windows Server 2016 or later, NetAdapter and NetTCPIP modules, Administrator
.LINK
    https://learn.microsoft.com/en-us/windows-server/networking/technologies/network-subsystem/net-sub-performance-tuning-nics
#>
[CmdletBinding()]
param (
    [Parameter(Mandatory = $true)]
    [string[]]$AdapterName,

    [ValidateRange(1, 256)]
    [int]$RssMaxProcessors,

    [ValidateRange(0, 255)]
    [int]$RssBaseProcessorNumber,

    [switch]$EnableJumboFrame,

    [ValidateRange(1514, 65535)]
    [int]$JumboPacketSize = 9014,

    [switch]$NoRestart
)

$restartParam = @{ NoRestart = [bool]$NoRestart }

# Confirm every adapter exists before changing anything.
foreach ($name in $AdapterName) {
    Get-NetAdapter -Name $name -ErrorAction Stop | Out-Null
}

# Report legacy Windows Server 2003-era values that Microsoft documents as ignored.
$tcpipParams = Get-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters"

foreach ($legacy in @("TcpWindowSize", "NumTcbTablePartitions", "MaxHashTableSize")) {
    if ($null -ne $tcpipParams.$legacy) {
        Write-Warning "Legacy value $legacy is set under Tcpip\Parameters. Windows ignores it; remove it to avoid confusion."
    }
}

# Report TCP Chimney. Microsoft: deprecated in Windows Server 2016, don't use it.
$offloadGlobal = Get-NetOffloadGlobalSetting

if ($offloadGlobal.Chimney -ne "Disabled") {
    Write-Warning "TCP Chimney global state is '$($offloadGlobal.Chimney)'. Chimney is deprecated; see Notes before changing it."
}

if ($offloadGlobal.ReceiveSideScaling -ne "Enabled") {
    Write-Warning "Global Receive Side Scaling is '$($offloadGlobal.ReceiveSideScaling)'. Enable it with Set-NetOffloadGlobalSetting -ReceiveSideScaling Enabled."
}

foreach ($name in $AdapterName) {
    # Receive Side Scaling: on, with an optional processor range.
    try {
        Enable-NetAdapterRss -Name $name @restartParam -ErrorAction Stop

        $rssParams = @{}

        if ($PSBoundParameters.ContainsKey("RssMaxProcessors")) {
            $rssParams.MaxProcessors = $RssMaxProcessors
        }

        if ($PSBoundParameters.ContainsKey("RssBaseProcessorNumber")) {
            $rssParams.BaseProcessorNumber = $RssBaseProcessorNumber
        }

        if ($rssParams.Count -gt 0) {
            Set-NetAdapterRss -Name $name @rssParams @restartParam -ErrorAction Stop
        }
    } catch {
        Write-Warning "RSS on '$name': $($_.Exception.Message)"
    }

    # Receive Segment Coalescing, checksum offload and LSO: on where the driver supports them.
    try {
        Enable-NetAdapterRsc -Name $name @restartParam -ErrorAction Stop
    } catch {
        Write-Warning "RSC on '$name': $($_.Exception.Message)"
    }

    try {
        Enable-NetAdapterChecksumOffload -Name $name @restartParam -ErrorAction Stop
    } catch {
        Write-Warning "Checksum offload on '$name': $($_.Exception.Message)"
    }

    try {
        Enable-NetAdapterLso -Name $name @restartParam -ErrorAction Stop
    } catch {
        Write-Warning "LSO on '$name': $($_.Exception.Message)"
    }

    # Jumbo frames through the standardized keyword, not the vendor display name.
    if ($EnableJumboFrame) {
        $jumbo = Get-NetAdapterAdvancedProperty -Name $name -RegistryKeyword "*JumboPacket" -ErrorAction SilentlyContinue

        if (-not $jumbo) {
            Write-Warning "Adapter '$name' does not expose *JumboPacket. Skipping."
        } elseif ($jumbo.ValidRegistryValues -and ($jumbo.ValidRegistryValues -notcontains [string]$JumboPacketSize)) {
            Write-Warning "Adapter '$name' accepts *JumboPacket values $($jumbo.ValidRegistryValues -join ', '), not $JumboPacketSize. Skipping."
        } else {
            Set-NetAdapterAdvancedProperty -Name $name -RegistryKeyword "*JumboPacket" -RegistryValue $JumboPacketSize @restartParam -ErrorAction Stop
        }
    }
}

# Receive window autotuning: make sure it is at the default, Normal.
$tuning = Get-NetTCPSetting | Where-Object { $_.AutoTuningLevelLocal -and $_.AutoTuningLevelLocal -ne "Normal" }

if ($tuning) {
    Write-Warning "AutoTuningLevelLocal is not Normal on: $(($tuning | ForEach-Object { $_.SettingName }) -join ', '). Setting Normal."
    Set-NetTCPSetting -AutoTuningLevelLocal Normal
}

# Summary.
Get-NetAdapterRss -Name $AdapterName |
    Format-Table -Property Name, Enabled, Profile, BaseProcessorNumber, MaxProcessors, NumberOfReceiveQueues -AutoSize

Get-NetAdapterRsc -Name $AdapterName |
    Format-Table -Property Name, IPv4Enabled, IPv4OperationalState, IPv4FailureReason -AutoSize

if ($EnableJumboFrame) {
    Get-NetAdapterAdvancedProperty -Name $AdapterName -RegistryKeyword "*JumboPacket" -ErrorAction SilentlyContinue |
        Format-Table -Property Name, @{ Name = "JumboPacket"; Expression = { $_.RegistryValue -join "," } } -AutoSize
}

Get-NetTCPSetting -SettingName Datacenter, Internet |
    Format-Table -Property SettingName, AutoTuningLevelLocal, CongestionProvider -AutoSize