OSI 7 LAYER OSI Model Application layer Presentation

OSI 7 LAYER

OSI Model Ø Application layer Ø Presentation layer Ø Session layer Ø Transport layer Ø Network layer Ø Datalink layer Ø Physical layer

หนาท OSI 7 layer Physical characteristics of interface and media - Type of medium, Topology � Representation of bits to Encoding - How 0 s and 1 s are changed to signals � Data rate - The number of bits sent each second � Synchronization of bits (�������� ) - Clock must be synchronized � Line configuration - Point-to-Point or Multipoint � Transmission mode - Simplex or Half-duplex or Full-duplex �

Physical layer

Datalink layer � Framing - Divide the stream of bits � Physical addressing - MAC (Media Access Control) address - Send locally � Flow control - Prevent overwhelming (���� ) the receiver � Error control - Error detection (����� ), - Retransmission damaged or lost frame - Add FCS (Frame Check Sequence) to the end of frame � Access control - Manage more devices are connected to the same link

Datalink layer

Network layer � Logical addressing - Send a packet across the network - IP (Internet Protocol) Address � Routing - When networks are connected to Internet, the devices route or switch the packets to correct final destination

Network layer

Transport layer � Port addressing - Specific process (running program) on devices � Segmentation & Reassembly - Message (data) is divided into transmittable segments - Sequence number use for reassemble the message � Connection control - Connectionless - Connection-oriented � Flow control � Error control

Transport layer

Session layer � Network dialog controller - Establishes, maintains and synchronizes the interaction among communication systems � Dialog control - Controlling the dialog between process (running program) - Half-duplex, Full-duplex � Synchronization - Add Checkpoint or synchronization to stream of data - Ex. – sending file

Session layer

Presentation layer � Concerned with the syntax and semantics of the information exchanged between two system � Translation - Different computers use different encoding system - Change information into common format � Encryption - Encryption/Decryption � Compression - Reduces the number of bits - Ex. – text, audio and video

Presentation layer

Application layer �Enable user (human or software) to access the network �User Interface and support for services �Services - File transfer - Mail services

Application layer