OSI 5 05 OSI - 응용계층 Sep 25, 2025 04 OSI - 전송계층 Sep 25, 2025 03 OSI - 네트워크계층 Sep 25, 2025 02 OSI - 데이터링크계층 Sep 25, 2025 01 OSI - 물리계층 Sep 25, 2025