OSI Layer Review

OSI Layer Review

The following table compares the functions performed at each OSI model layer.

Layer		Description and Keywords	Protocols	Devices	Encapsulation
Application		Provides an interface for a service to operate Communication partner identification	HTTP Telnet FTP TFTP SNMP		User information and data
Presentation		Data format (file formats) Encryption, translation, and compression Data format and exchange	JPEG, BMP, TIFF, PICT MPEG, WMV, AVI ASCII, EBCDIC MIDI, WAV		Data
Session		Keeps data streams separate (session identification) Set up, maintain, and tear down communication sessions	SQL NFS ASP RPC X window		Data
Transport		Reliable (connection-oriented) and unreliable (connectionless) communications End-to-end flow control Port and socket numbers Segmentation, sequencing, and combination	TCP (connection-oriented) UDP (connectionless)		Segments
Network		Logical addresses Path determination (identification and selection) Routing packets	IP IPX AppleTalk DECNET	Routers Layer 3 switches	Packets
Data Link	Logical Link Control (LLC)	Convert bits into bytes and bytes into frames MAC address, hardware address Logical network topology Media access Flow control Acknowledgements Buffering Windowing Parity and CRC	LAN protocols: 802.2 (LLC), 802.3 (Ethernet), 802.5 (Token Ring), 802.11 (Wireless) WAN protocols: HDLC, PPP, Frame Relay, ISDN, ATM	Network Interface Card (NIC) transceivers Switch Bridge	Frames
	Media Access Control (MAC)
Physical		Move bits across media Cables, connectors, pin positions Electrical signals (voltage, bit synchronization) Physical topology (network layout)	EIA/TIA 232 (serial signaling) V.35 (modem signaling) Cat5 RJ45	Transmission media (cable and wires) Media connectors Transceivers (including transceivers built into NICs) Modems Repeaters Hubs Multiplexers CSUs/DSUs Wireless Access Points	Bits

 

 

 

 

Credit: Testout 640-802 CCNA Notes