# Multipath network transmission (/en/realtime-media/video/build/manage-connection-and-quality/multipath-transmission/windows)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

A growing number of electronic devices support simultaneous network access through multiple connections, such as Wi-Fi and cellular, or Wi-Fi and dual-SIM cellular. Each connection is independent of the actual network transmission path and does not share bandwidth bottlenecks.

This page explains how to implement multipath network transmission in your Video Calling project.

## Understand the tech [#understand-the-tech]

Starting with v4.6.0, Video SDK adds a network transmission feature called Multipath. This feature is designed for devices that support multiple network interfaces, including 5G, Wi-Fi, and LAN. Multipath helps reduce or even eliminate poor user experiences caused by weak network conditions. In lab tests, under weak network conditions with frequent bandwidth jitter, enabling Multipath reduces lag by more than 50% while maintaining image quality and latency.

Multipath improves real-time audio and video experiences that require stable transmission in poor network conditions, including video conferencing, online education, IoT parallel operations, and remote production and broadcasting.

## Prerequisites [#prerequisites]

Before you begin, make sure you have:

      
  
      
  
      
  
      
    * A Windows device running Vista or later, with two or more active network interfaces such as Wi-Fi and Ethernet.

    
  
* Basic audio and video interaction functions already implemented in your project. See [Quickstart](/en/realtime-media/video/get-started-sdk).

## Implementation [#implementation]

      
  
      
  
      
  
      
    ### Multipath APIs [#multipath-apis-3]

    Video SDK supports enabling and configuring Multipath through the following `ChannelMediaOptions` fields:

    ```cpp
    struct ChannelMediaOptions {
      // ...
      Optional<bool> enableMultipath;
      Optional<MultipathMode> uplinkMultipathMode;
      Optional<MultipathMode> downlinkMultipathMode;
      Optional<MultipathType> preferMultipathType;
    };
    ```

    Use `enableMultipath` to enable multipath transmission. Once enabled, the SDK supports two transmission modes:

    * **Dynamic mode** (default): Dynamically selects the optimal transmission path based on network conditions. This mode is suitable for traffic-sensitive scenarios with high user experience requirements, such as conferences and education. In this mode, you can use `preferMultipathType` to specify a preferred network path, such as Wi-Fi or mobile network.

    * **Full redundancy mode**: Sends data simultaneously across all available network paths. This mode is suitable for scenarios where traffic use is less sensitive but a highly reliable user experience is required, such as outdoor production, broadcasting, and parallel operation. This mode incurs additional fees. Contact [support@agora.io](mailto\:support@agora.io) to enable it.

    You can configure the transmission mode separately for uplink (`uplinkMultipathMode`) and downlink (`downlinkMultipathMode`).

    When Multipath is enabled, the SDK reports transmission statistics for each path in real time through the `onMultipathStats` callback. These statistics include traffic consumption for each network type and real-time performance metrics for each path, making it easier to monitor and optimize network performance.

    ```cpp
    struct MultipathStats {
      uint32_t lanTxBytes;
      uint32_t lanRxBytes;
      uint32_t wifiTxBytes;
      uint32_t wifiRxBytes;
      uint32_t mobileTxBytes;
      uint32_t mobileRxBytes;
      int activePathNum;
      const PathStats* pathStats;
    };
    ```

    ### Sample code [#sample-code-3]

    ```cpp
    // Initialize UI elements related to multipath transmission
    m_cmbMultipathMode.InsertString(0, _T("Duplicate"));
    m_cmbMultipathMode.InsertString(1, _T("Dynamic"));
    m_cmbMultipathMode.SetCurSel(0);

    // Initialize multipath transmission controls
    m_staEnableMultipath.SetWindowText(_T("Enable Multipath:"));
    m_chkEnableMultipath.SetCheck(BST_UNCHECKED);

    ChannelMediaOptions options;
    options.enableMultipath = (m_chkEnableMultipath.GetCheck() == BST_CHECKED);

    int modeIndex = m_cmbMultipathMode.GetCurSel();
    MultipathMode mode = (modeIndex == 0) ? Duplicate : Dynamic;

    options.uplinkMultipathMode = mode;
    options.downlinkMultipathMode = mode;
    options.preferMultipathType = WIFI;

    void CMultipathRtcEngineEventHandler::onMultipathStats(const MultipathStats& stats)
    {
      if (m_hMsgHanlder)
      {
        MultipathStats* statsPtr = new MultipathStats(stats);
        ::PostMessage(m_hMsgHanlder, WM_MSGID(EID_MULTIPATH_STATS), (WPARAM)statsPtr, 0);
      }
    }
    ```

    
  
## Reference [#reference]

This section contains content that completes the information on this page, or points you to documentation that explains other aspects of this feature.

      
  
      
  
      
  
      
    ### API reference [#api-reference-3]

    * [ChannelMediaOptions](https://api-ref.agora.io/en/video-sdk/cpp/4.x/API/class_channelmediaoptions.html)
    * [onMultipathStats](https://api-ref.agora.io/en/video-sdk/cpp/4.x/API/class_irtcengineeventhandler.html#callback_irtcengineeventhandler_onmultipathstats)