debian13bbr

Question

debian13bbr

Accepted Answer

To enable TCP BBR (Bottleneck Bandwidth and Round-trip propagation time) on Debian 13 (Trixie), you can follow these steps. Debian 13 kernels include the `tcp_bbr` module by default, making the setup straightforward.

### 1. Load the BBR Kernel Module
First, ensure the BBR module is loaded into the kernel.
*   **Load it now:**
    ```bash
    sudo modprobe tcp_bbr
    ```
*   **Ensure it persists after reboot:**
    ```bash
    echo "tcp_bbr" | sudo tee /etc/modules-load.d/bbr.conf
    ```

### 2. Configure Sysctl Parameters
You need to tell the system to use BBR as the default congestion control algorithm and set the fair queueing (`fq`) scheduler, which is recommended for BBR.

1.  Create or edit the configuration file:
    ```bash
    sudo nano /etc/sysctl.d/99-bbr.conf
    ```
2.  Add the following lines to the file:
    ```text
    net.core.default_qdisc = fq
    net.ipv4.tcp_congestion_control = bbr
    ```
3.  Save and exit (in `nano`, press `Ctrl+O`, `Enter`, then `Ctrl+X`).

### 3. Apply and Verify
*   **Apply the changes:**
    ```bash
    sudo sysctl -p /etc/sysctl.d/99-bbr.conf
    ```
*   **Verify it is active:**
    Run the following command to check the current congestion control algorithm:
    ```bash
    sysctl net.ipv4.tcp_congestion_control
    ```
    It should return `net.ipv4.tcp_congestion_control = bbr`.

*   **Verify the module is loaded:**
    ```bash
    lsmod | grep bbr
    ```
    This should show `tcp_bbr` in the output.

BBR is now enabled on your system and will persist across reboots.