#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : Gigabit LAN transfers run at a fraction of the speed
    Fix   : Measure what SMB is costing before changing it
    Source: https://jbtecwiz.com/support/win-net-slow-lan

    Run as     : Elevated PowerShell on both ends
    Expect     : 25 minutes
    Risk       : medium
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Only file shares are slow, and only to certain servers.

    HOW TO UNDO IT
    Set-SmbClientConfiguration and Set-SmbServerConfiguration accept the
    original values recorded in step one.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 4"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  Gigabit LAN transfers run at a fraction of the speed' -ForegroundColor White
Write-Host '  Measure what SMB is costing before changing it' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   Reversible   25 minutes'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'See the dialect, whether multichannel is in use, and whether it is signing or encrypting.' -Command {
    Get-SmbConnection | Format-Table ServerName,ShareName,Dialect,Encrypted,Signed
    Get-SmbClientConfiguration | Format-List EnableMultiChannel,RequireSecuritySignature,EnableBandwidthThrottling
}

Invoke-Step -Number 2 -Do 'On the server, check the same.' -Command {
    Get-SmbServerConfiguration | Format-List EnableSMB2Protocol,RequireSecuritySignature,EncryptData,EnableMultiChannel
}

Invoke-Step -Number 3 -Do 'If signing is required and the CPU is the bottleneck, the answer is a faster server or more channels -- not turning signing off. Signing is what stops a man in the middle rewriting the files in transit.' -Why 'Every forum answer to this suggests disabling SMB signing. On a domain network it is required for SYSVOL by default and disabling it opens a real attack. Measure first.' -Manual

Invoke-Step -Number 4 -Do 'Enable multichannel if both ends have more than one adapter -- it multiplies throughput without weakening anything.' -Command {
    Set-SmbClientConfiguration -EnableMultiChannel $true -Force
    Set-SmbServerConfiguration -EnableMultiChannel $true -Force
}

Write-Rule "  Confirm it worked"
Show-Prose 'Transfer rate improves and the connection is still shown as Signed.' 'White'
Write-Host ''
if (-not $DryRun) {
    Get-SmbMultichannelConnection | Format-Table Server,ClientIpAddress,ServerIpAddress,CurrentChannels
}

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/win-net-slow-lan' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Set-SmbClientConfiguration and Set-SmbServerConfiguration accept the original values recorded in step one.' 'DarkGray'
Write-Rule