DOTNET: TLS & Its Versions impact on Performance

Program.cs

using System.Diagnostics;
using System.Net;
using System.Security.Authentication;
using System.Threading;

// Simple .NET minimal API to demo TLS 1.2 vs TLS 1.3 impact
// and expose basic in-process metrics at /metrics

var builder = WebApplication.CreateBuilder(args);

// Decide TLS version from env var: TLS_VERSION=12 or TLS_VERSION=13
// Default = 1.2
var tlsEnv = Environment.GetEnvironmentVariable("TLS_VERSION") ?? "12";
var useTls13 = tlsEnv.Trim() == "13";
var tlsLabel = useTls13 ? "TLS 1.3" : "TLS 1.2";

// Configure Kestrel to listen on HTTPS 5001 with selected TLS
builder.WebHost.ConfigureKestrel(options =>
{
    options.Listen(IPAddress.Loopback, 5001, listen =>
    {
        listen.UseHttps(https =>
        {
            https.SslProtocols = useTls13 ? SslProtocols.Tls13 : SslProtocols.Tls12;
        });
    });
});

var app = builder.Build();

Console.WriteLine("=========================================");
Console.WriteLine(" TLS Demo API");
Console.WriteLine($" Using: {tlsLabel}");
Console.WriteLine(" Listening on: https://localhost:5001");
Console.WriteLine(" Endpoints:");
Console.WriteLine("   GET /ping    - simple test endpoint");
Console.WriteLine("   GET /metrics - shows basic latency metrics");
Console.WriteLine("=========================================");

// Simple in-process metrics
long totalRequests = 0;
long totalDurationTicks = 0;
long maxDurationTicks = 0;

// A simple endpoint you can hit from Postman / curl
// We simulate a tiny bit of work to make TLS overhead visible.
app.MapGet("/ping", async () =>
{
    var sw = Stopwatch.StartNew();

    // Simulate some app work: CPU + async wait
    // (You can change this to Task.Delay(5) or a CPU loop if you want.)
    await Task.Delay(5);

    sw.Stop();

    Interlocked.Increment(ref totalRequests);
    Interlocked.Add(ref totalDurationTicks, sw.ElapsedTicks);

    // Update max duration
    long oldMax, newVal;
    do
    {
        oldMax = Interlocked.Read(ref maxDurationTicks);
        newVal = sw.ElapsedTicks > oldMax ? sw.ElapsedTicks : oldMax;
    } while (Interlocked.CompareExchange(ref maxDurationTicks, newVal, oldMax) != oldMax);

    return Results.Text("pong");
});

// Metrics endpoint so you can see load numbers in the app itself
app.MapGet("/metrics", () =>
{
    var req = Interlocked.Read(ref totalRequests);
    var totalTicks = Interlocked.Read(ref totalDurationTicks);
    var maxTicks = Interlocked.Read(ref maxDurationTicks);

    var totalMs = TimeSpan.FromTicks(totalTicks).TotalMilliseconds;
    var avgMs = req > 0 ? totalMs / req : 0.0;
    var maxMs = TimeSpan.FromTicks(maxTicks).TotalMilliseconds;

    var result = new
    {
        tls = tlsLabel,
        totalRequests = req,
        averageDurationMs = avgMs,
        maxDurationMs = maxMs
    };

    return Results.Json(result);
});

app.Run();