We've encountered a particularly frustrating scenario where Windows 7 clients experience abrupt Remote Desktop Protocol (RDP) disconnections from a Windows Server 2008 machine. The error message states: "Because of a protocol error, this session will be disconnected. Please try connecting to the remote computer again." Interestingly, Mac clients using Cord remain unaffected, pointing to a Windows-specific protocol compatibility issue.

The RDP stack between Windows 7 and Server 2008 has known quirks. The server uses RDP 6.1 while Windows 7 defaults to 7.0. This version mismatch can cause cryptographic negotiation failures. Check your current RDP settings with this PowerShell command:

Get-ItemProperty -Path "HKLM:\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp" -Name "SecurityLayer"

Packet captures reveal these disconnections often occur during:

• Certificate renegotiation
• Bitmap compression updates
• Session keepalive timeouts

Try adjusting the keepalive settings (non-disruptive change):

reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters" /v KeepAliveTime /t REG_DWORD /d 300000 /f
reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters" /v KeepAliveInterval /t REG_DWORD /d 1000 /f

For Windows 7 clients, modify the RDP file to enforce compatibility:

screen mode id:i:2
use multimon:i:0
session bpp:i:32
winposstr:s:0,1,0,0,800,600
compression:i:1
keyboardhook:i:2
audiocapturemode:i:0
videoplaybackmode:i:1
connection type:i:7
networkautodetect:i:1
bandwidthautodetect:i:1
displayconnectionbar:i:1
enableworkspacereconnect:i:0
disable wallpaper:i:1
allow font smoothing:i:0
allow desktop composition:i:0
disable full window drag:i:1
disable menu anims:i:1
disable themes:i:0
disable cursor setting:i:0
bitmapcachepersistenable:i:1

These registry modifications can stabilize the connection without session interruption:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp]
"SecurityLayer"=dword:00000002
"UserAuthentication"=dword:00000001
"MinEncryptionLevel"=dword:00000003
"fDisableEncryption"=dword:00000000

When immediate stability is required, consider these alternatives:

1. Use RemoteApp instead of full desktop sessions
2. Implement a jump server with newer RDP versions
3. Configure session shadowing for critical applications

For developers needing uninterrupted access, this C# snippet helps monitor RDP stability:

using System;
using System.Diagnostics;

class RdpMonitor {
    static void Main() {
        var timer = new System.Timers.Timer(60000);
        timer.Elapsed += (sender, e) => CheckRdpSession();
        timer.Start();
        Console.ReadLine();
    }

    static void CheckRdpSession() {
        var sessions = Process.GetProcessesByName("mstsc");
        if (sessions.Length == 0) {
            EventLog.WriteEntry("Application", 
                "RDP session terminated unexpectedly", 
                EventLogEntryType.Warning);
        }
    }
}

I've been wrestling with this exact issue on a production Windows Server 2008 R2 system where Windows 7 clients experience sudden disconnections with the protocol error message. What makes this particularly frustrating is that:

• The session remains active server-side
• Mac clients via Cord work flawlessly
• Critical applications can't tolerate session resets

Before diving deep, run these commands on both client and server to gather baseline information:

# On Windows 7 client:
netsh interface tcp show global
quser /server:yourserver

# On Server 2008:
query session
reg query "HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server" /v KeepAliveEnable

The protocol error suggests TCP/IP stack issues. Check these potential culprits:

# Disable TCP Chimney Offloading (often problematic with RDP)
netsh int tcp set global chimney=disabled

# Verify MTU settings (fragmentation can cause drops)
ping -f -l 1472 yourserver

These registry modifications can help stabilize the connection:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services]
"KeepAliveEnable"=dword:00000001
"KeepAliveInterval"=dword:00000001
"fDisableAutoReconnect"=dword:00000000

Create a custom RDP file with these parameters:

screen mode id:i:2
use multimon:i:0
session bpp:i:32
winposstr:s:0,1,738,305,1638,905
compression:i:1
keyboardhook:i:2
audiocapturemode:i:0
videoplaybackmode:i:1
connection type:i:2
displayconnectionbar:i:1
disable wallpaper:i:1
allow font smoothing:i:1
allow desktop composition:i:0
disable full window drag:i:1
disable menu anims:i:1
disable themes:i:0
disable cursor setting:i:0
bitmapcachepersistenable:i:1

When the disconnection occurs, look for these packet patterns:

# Filter for RDP protocol issues
rdp && (tcp.analysis.retransmission || tcp.analysis.window_update)

# Common problematic patterns
tcp.flags.reset == 1
tcp.window_size == 0

If immediate resolution isn't possible, consider these temporary measures:

# PowerShell script to auto-reconnect
while($true) {
    try {
        mstsc /v:yourserver /f /admin
        Start-Sleep -Seconds 30
    }
    catch {
        Write-Host "Reconnecting..." -ForegroundColor Yellow
    }
}