> For the complete documentation index, see [llms.txt](https://http3-explained.haxx.se/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://http3-explained.haxx.se/ja/the-protocol/feature-trans-app.md).

# トランスポートとアプリケーションレベル

IETF QUIC プロトコルはトランスポートプロトコルであり、その上に他のアプリケーションプロトコルも使用可能です。

最も主要なアプリケーションレイヤープロトコルは HTTP/3 (h3) です。

トランスポートレイヤーではコネクションとストリームをサポートします。

従来の Google 版の QUIC はトランスポートと HTTP が一括で動作するよう一つにまとめられており、HTTP/2 フレームを UDP 上で送ることにより特化したプロトコルでした。


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