Osi Model

Front 1

Layer 1: Physical Layer

Back 1

Layer 1
Defines physical means of sending data over network devices
Interface between network medium and devices
Define optical, electrical, and mechanical characteristics.
Specification of voltage, wire speed, and cable pinouts
Ex: Ethernet, 802.3, 802.5

Front 2

Layer 2: Data Link Layer

Back 2

Layer 2
Provides framing and sequencing
Detects and corrects received frame errors
Combinations of bits into bytes and bytes into frames
Access to media using MAC address
Ex: HDLC, Frame relay, PPP

Front 3

Layer 3: Network Layer

Back 3

Layer 3
Determines how data is transferred among network devices
Route packets according to the unique network addresses
Provides flow and congestion control to prevent network resource depletion.
Ex: IP, IPX

Front 4

Layer 4: Transport Layer

Back 4

Layer 4
Manages end to end message delivery in network
Provides reliable and sequential packet delivery through error recovery and flow control mechanisms
Provides connectionless oriented packet delivery
Multiplexing
Ex: TCP, UDP

Front 5

Layer 5: Session Layer

Back 5

Layer 5
Manages user sessions and dialogues
Controls establishment and termination of logical links between users
Reports upper layer errors
Ex: RPC, SQL, NetBios

Front 6

Layer 6: Presentation Layer

Back 6

Layer 6
Masks the differences of data formats between dissimilar systems
Specifies architecture-independent data transfer format
Encodes and decodes data; Encrypts and decrypts data; compress and decompress data.
Ex: JPEG, ASCII,GIF,MPEG

Front 7

Layer 7: Application Layer

Back 7

Layer 7
Interface between network and application software.
Provides standardized services such as virtual terminal, file and job transfer, and operation.
Ex: Telnet, HTTP, FTP, WWW browsers, SMTP gateway, SNMP