DOTNET: TLS & Its Versions impact on Performance

This will be a fun little lab. Let’s make one self-contained Program.cs you can run from command line and flip between TLS 1.2 and TLS 1.3 without changing code.

We’ll also add a /metrics endpoint so you can see basic latency stats directly from the app.

1. One-page complete code (Program.cs)

Create a new minimal API:

dotnet new web -n TlsTlsDemoApi
cd TlsTlsDemoApi
Code language: JavaScript (javascript)

Now replace the entire contents of Program.cs with this:

2. How to run with TLS 1.2 vs TLS 1.3

🔹 Windows PowerShell

Run with TLS 1.2:

$env:TLS_VERSION = "12"
dotnet run
Code language: PHP (php)

You’ll see:

Using: TLS 1.2
Listening on: https://localhost:5001
Code language: JavaScript (javascript)

Run with TLS 1.3:

Stop the app, then:

$env:TLS_VERSION = "13"
dotnet run
Code language: PHP (php)

You’ll see:

Using: TLS 1.3
Listening on: https://localhost:5001
Code language: JavaScript (javascript)

3. How to “load test” it quickly

You can use Postman, or just use curl loops from command line.

🔹 Simple curl loop (Linux/macOS / Git Bash)

for i in {1..200}; do curl -k -s "https://localhost:5001/ping" > /dev/null; done
Code language: JavaScript (javascript)

🔹 Simple PowerShell loop (Windows)

1..200 | ForEach-Object {
    curl -k -s "https://localhost:5001/ping" > $null
}
Code language: JavaScript (javascript)

Then check metrics:

curl -k "https://localhost:5001/metrics"
Code language: JavaScript (javascript)

You’ll see something like:

{
  "tls": "TLS 1.2",
  "totalRequests": 200,
  "averageDurationMs": 6.3,
  "maxDurationMs": 15.2
}
Code language: JSON / JSON with Comments (json)

Run again with TLS 1.3 and compare:

• averageDurationMs
• maxDurationMs

Under heavier load (larger loops, multiple clients), you’ll see TLS 1.3 usually gives better latency and smoother max values, especially when handshake overhead matters (cold clients).

4. Where to see CPU / memory

You asked:

“Do we have any way to see the load metrics in the code itself?”

We did that with /metrics (per-request latency). For CPU and memory, best is:

🔹 Option A: dotnet-counters (recommended)

Find PID:

dotnet-counters ps

Then:

dotnet-counters monitor --process-id <PID> System.Runtime
Code language: HTML, XML (xml)

Watch:

• cpu-usage
• gc-heap-size
• gen-0-gc-count etc.

Run your load loop and watch how TLS 1.2 vs 1.3 behaves.

🔹 Option B: Task Manager

Just open Task Manager → Details → dotnet.exe, watch CPU and Memory while you hit /ping.

5. How to use this in your understanding

1. Start with TLS 1.2 (TLS_VERSION=12).
2. Run a curl/Postman loop, show /metrics.
3. Show CPU/memory with dotnet-counters or Task Manager.
4. Switch to TLS 1.3 (TLS_VERSION=13).
5. Repeat same load → compare metrics.
6. Explain:
   • Less handshake overhead
   • Better latency
   • Lower CPU under same load (especially when doing many short connections).

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

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