It’s easy to remember the sequence of OSI Model 7 Layers using this simple sentence: “All people seem to need data processing.”
All = Application Layer
People= Presentation Layer
Seem = Session Layer
To = Transport Layer
Need = Network Layer
Data = Data Link Layer
Processing = Physical Layer
Application Layer (DATA)
Application Layer provides Interface between users and machines.
Protocols of this layer are: HTTP, HTTPS, FTP, TFTP, Telnet, SNMP, DNS, Rlogin, SMTP, POP3, IMAP, and LDAP.
Presentation Layer (DATA)
This layer facilitates the presentation of Data to the upper layer. Mainly, Provide Encoding Scheme & Encryption formation.
Protocols of this layer: JPEG, BMP, GIF, TIF, PNG, MP3, MIDI, ASCII & ANSI etc.
Session Layer (DATA)
This layer provides virtual agreement between two end communication devices.
Functions of this layer: Establishment, Management & Termination
The best example to explain this layer is telephone call in which first you established the connection, then exchange a message and finally terminate the session.
Protocols of this layer: SIP, NFS, SQL, ASP, RDBMS
The above three layers are known as the software layer.
Transport Layer (SEGMENT)
This layer is responsible for Control of Data flow and, if an error occurs, reconnect the data and re-transmit.
Functions of this layer: Handshaking, Acknowledgement and Sequencing
Protocols of this layer: TCP, UDP, SPX
Network Layer (Packet)
This layer is used for communication to remote networks.
Functions of this layer: Sorting, Filtering and Distribution
Protocols of this layer: Routed Protocol: IP/IPX/Apple talk
Routing Protocol: IGP, EGP, BGP, EBGP, IBGP, RIP, IGRP, RIP, OPSF, IS-IS
Data Link Layer (Frame)
Function of this layers: Error Detection and Control of Data
Uniqueness of this layer: MAC address
Protocols of this layer: PPP, HDLC, ATM, Frame Relay, SLIP, Ethernet
Physical Layer (Binary)
This involves media, move bits between devices
MAC Address: Information Delivered
IP Address: Carrier of Information
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