When the production server consistently aborts requests at exactly 1 minute 19 seconds (79,000ms) while development environments complete similar requests in 1 minute 44 seconds, we're seeing classic signs of infrastructure-level interference. The Win32 status code 995 (0x3E3) specifically indicates ERROR_OPERATION_ABORTED - meaning an overlapped I/O operation was cancelled before completion.

In our specific case with 650KB responses:

HTTP Request → IIS Worker Process → Application Code Execution → 
Response Buffering → Network Transmission → Firewall Interrupt

The access log tells the story:

200 0 995 0 76933  # 995 = Thread aborted by external factor

Firewalls and load balancers often have default idle connection timeouts. Common culprits:

• Azure Application Gateway: Default 4 minute timeout
• F5 BIG-IP: Typical 300-second timeout
• Windows Firewall: 60-120 second thresholds

1. Network Capture:

netsh trace start scenario=netconnection capture=yes tracefile=C:\temp\nettrace.etl
# Reproduce the issue
netsh trace stop

2. IIS Configuration Check:

<system.webServer>
  <asp scriptTimeout="00:05:00" />
  <serverRuntime uploadReadAheadSize="49152" />
</system.webServer>
<system.web>
  <httpRuntime executionTimeout="300" maxRequestLength="10240" />
</system.web>

Keep-alive Implementation:

public class KeepAliveHandler : IHttpHandler 
{
    public void ProcessRequest(HttpContext context)
    {
        context.Response.Buffer = false;
        context.Response.Write("PING");
        context.Response.Flush();
        
        // Main processing here
        Thread.Sleep(120000); // Simulate long operation
        
        context.Response.Write("COMPLETE");
    }
}

Web.config Adjustments:

<configuration>
  <system.webServer>
    <webSocket enabled="false" />
    <asp enableChunkedEncoding="false" />
  </system.webServer>
</configuration>

Factor	Production	Development
OS	Windows Server 2008	Windows 7
IIS Version	7.0	7.5
Default Timeout	120s (typical)	No enforced timeout

To confirm firewall interference:

Test-NetConnection -ComputerName endpoint.com -Port 443 -InformationLevel Detailed

Remember that some network devices log connection resets separately from their main logs. Always check:

• Wireshark/Tcpdump captures
• Proxy server logs
• TCP/IP stack settings (netsh int tcp show global)

---

When our production server consistently aborts HTTP requests at exactly 1 minute 19 seconds (79,000ms) while the same request completes in 1:44 on development machines, we're seeing classic symptoms of infrastructure-level interference. The Win32 status code 995 (0x3E3) translates to ERROR_OPERATION_ABORTED, indicating an external force terminated the connection.

# Sample IIS log entry showing the abort
2023-11-15 14:22:33 192.168.1.100 GET /api/large_report - 80 - 10.0.0.1 Mozilla/5.0 200 0 995 0 76933

Notice the critical indicators:

• sc-status 200 suggests IIS thought the request was successful
• sc-bytes 0 confirms no data actually reached the client
• sc-win32-status 995 reveals the underlying Windows abort
• time-taken 76933ms (76.9s) shows when the abort occurred

Many corporate firewalls (especially Check Point, Palo Alto, or Cisco ASA) enforce default TCP idle timeouts between 60-90 seconds. When dealing with long-running requests that don't frequently flush data:

// ASP.NET example vulnerable to firewall timeouts
public async Task GenerateReport() 
{
    var data = await GetLargeDataset(); // Takes 60+ seconds
    return Json(data); // Single flush at end
}

1. Protocol-Level Keepalives

Force periodic TCP packets to bypass idle detection:

// In Global.asax.cs
protected void Application_BeginRequest()
{
    Response.BufferOutput = false;
    Response.Write(" "); // Initial flush
    Response.Flush();
}

2. IIS Configuration Tweaks

<system.webServer>
  <serverRuntime frequentHitThreshold="1" 
                frequentHitTimePeriod="00:00:30" 
                frequentHitSampleInterval="00:00:05"/>
</system.webServer>

3. Application-Level Heartbeats

For streaming scenarios:

// Middleware example
app.Use(async (context, next) => 
{
    var buffer = new MemoryStream();
    var originalBody = context.Response.Body;
    context.Response.Body = buffer;
    
    await next();
    
    // Flush every 30 seconds
    if(buffer.Length > 0) 
    {
        await originalBody.WriteAsync(buffer.GetBuffer(), 0, (int)buffer.Length);
        await originalBody.FlushAsync();
        await Task.Delay(30000);
    }
});

Use PowerShell to test firewall behavior:

# Simulate long request with periodic data
1..100 | % {
    Write-Output "Keepalive $_"
    Start-Sleep -Seconds 15
} | Out-File -FilePath \\server\share\test.txt

Monitor with Wireshark for TCP RST packets appearing at the timeout threshold.