OSI and TCP-IP Network Models


Just a note for myself to remember about OSI 7 Layers and TCP/IP.

OSI 7 Layers

Layer # Name Mnemonic Encapsulation Units Devices or Components Keywords/Description
7 Application All data PC Network services for application processes, such as file, print, messaging, database services
6 Presentation People data Standard interface to data for the application layer. MIME encoding, data encryption, conversion, formatting, compression
5 Session Seem data Interhost communication. Establishes, manages and terminates connection between applications
4 Transport To segments End-to-end connections and reliability. Segmentation/desegmentation of data in proper sequence. Flow control
3 Network Need packets router Logical addressing and path determination. Routing. Reporting delivery errors
2 Data Link Data frames bridge, switch, NIC Physical addressing and access to media. Two sublayers: Logical Link Control (LLC) and Media Access Control (MAC)
1 Physical Processing bits repeater, hub, transciever Binary transmission signals and encoding. Layout of pins, voltages, cable specifications, modulation

OSI comparision with TCP/IP Protocol Stack

OSI # OSI Layer Name TCP/IP # TCP/IP Layer Name Encapsulation Units TCP/IP Protocols
7 Application 4 Application data FTP, HTTP, POP3, IMAP, telnet, SMTP, DNS, TFTP
6 Presentation data
5 Session data
4 Transport 3 Transport segments TCP, UDP
3 Network 2 Internet packets IP
2 Data Link 1 Network Access frames
1 Physical bits