OSI 7계층 모형

OSI Model
Layer	Protocol Data Unit(PDU)	Function	Examples
7.Application	Data	High-level APIs including resource sharing, remote file access, directory services and virtual terminals	RTP?
6.Presentation		Translation of data between a networking service and an application, including character encoding, data compression and encryption/decryption	CSS, GIF, HTML, XML, JSON
5.Session		Managing communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes	RPC, TLS, FTP, HTTP, HTTPS, SMTP, SSH, Telnet
4.Transport	Segment/Datagram	Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing	TCP, UDP
3.Network	Packet	Structuring and managing a multi-node network, including addressing, routing and traffic control	ICMP, IPsec, IPv4, IPv6
2.Data Link	Frame	Reliable transmission of data frames between two nodes connected by a physical layer	IEEE 802.2, MAC, PPP
1.Physical	Bit	Transmission and reception of raw bit streams over a physical medium	DOCSIS, Ethernet physical layer, ISDN, RS-232