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OSI Model
INTRODUCTION
The OSI Model (Open Systems Interconnection Model) is a conceptual framework used to describe the functions of a networking system. The OSI model characterizes computing functions into a universal set of rules and requirements in order to support interoperability between different products and software.
PHYSICAL LAYER
Physical characteristics of interface and medium (Transmission medium)
Representation of bits (stream of bits (0s or 1s) with no interpretation and encoded into signals)
Line configuration (Point-to-Point, Point-to-Multipoint)
Physical topology
Transmission mode (Simplex, half duplex, full duplex)
DATALINK LAYER
Data link layer is responsible for moving frames from one hop (Node) to the next.
Concerned:
Framing (stream of bits into manageable data units) Physical addressing (MAC Address)
Flow Control (mechanism for overwhelming the receiver) Error Control (trailer, retransmission)
Access Control (defining master device in the same link)
NETWORK LAYER
The network layer is responsible for the delivery of individual packets from the source host to the destination host.
Concerned:
Logical addressing (IP Address)
Routing (Source to destination transmission between networks)
TRANSPORT LAYER
The transport layer is responsible for the delivery of a message from one process to another
Concerned:
Service-point addressing (Port address)
Sequence Number (data reassembly)
Segmentation and reassembly (Sequence number)
SESSION LAYER
The session layer is responsible for authentication & authorization.
Concerned:
Session establishment (Starts & terminates sessions)
Dialog Control (allows to communicate 2 systems in Half Duplex/Full duplex)
Synchronization (checks error in fixed time interval to avoid errors)
PRESENTATION LAYER
The presentation layer is responsible for translation, compression and encryption
Concerned:
Translation (interoperability between different encoding system) Encryption (Privacy schemes)
Compression (data compression)
APPLICATION LAYER
The application layer is responsible for providing services to the user.
Concerned:
Web surfing protocols
File transfer, access and management Mail services
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