osi networking
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Seven Layer of OSI Model
OSI reference model
Open System Interconnection (OSI) represents a generalization of concept of inter-process communication so that any open system may be technically able to communicate with another open system.
In the OSI reference model, the communication functions are divided into a hierarchy of seven layers. It also referred to as 7-layer model.
The transmission medium is not included in the seven layers and it can be regarded as 0th layer.
Layer Architecture of the OSI Reference Model
The Application Layer the seventh layer in
OSI network model.
Application Layer is the top-most layer of
the seven layered Open Systems
Interconnection (OSI) network model.
As the highest layer in the OSI model, the
application layer provides services to the
user of the OSI environment.
Application Layer•Login , password checking, file transfer
are some of the functions of the
application layer.
•. Real traffic data will be often
generated from the Application Layer.
This may be a web request generated
from HTTP protocol, a command from
telnet protocol, a file download request
from FTP protocol etc.
The purpose of the presentation layer is to present the information to communicating application entities in a way that preserves the meaning while resolving the syntax differences.
There are three syntactic version of data being transferred, the syntax used by the application entity of the originator of the data, the syntax used by the recipient of the data, and the “transfer” syntax used to transfer the data between presentation entities.
Application layer
Presentation layer
Transfer syntax
Local syntaxLocal syntax
Local and transfer syntax of the presentation layer
The purpose of the session layer is to
provide the means necessary for the
cooperating presentation entities to
organize and synchronize their data
exchange.
The session layer provides two-way
simulaneous, two-way alernate, and
one-way communication services.
Transport layer provides transparent
transfer of data between end systems,
or hosts, and is responsible for end-to-
end error recovery and flow control. It
ensures complete data transfer.
Layer 4 Transport examples include
SPX, TCP, UDP.
Network layer
Network layer provides switching and routing technologies, creating logical paths, known as virtual circuits, for transmitting data from node to node. Routing and forwarding are functions of this layer, as well as addressing,internetworking, error handling, congestion control and packet sequencing.
Layer 3 Network examples include AppleTalk DDP, IP, IPX.
Data link layer
At this layer, data packets
are encoded and decoded into bits.
The data link layer is divided into two
sub layers: The Media Access Control
(MAC) layer and the Logical Link
Control (LLC) layer
Layer 2 Data Link examples include
PPP, FDDI, ATM, IEEE 802.5/ 802.2,
IEEE 802.3/802.2, HDLC, Frame
Relay.
Physical layer
Physical layer conveys the bit stream -
electrical impulse, light or radio
signal — through the network at the
electrical and mechanical level.
It provides the hardware means of
sending and receiving data on a
carrier, including defining cables,
cards and physical aspects.
Physical layer
Physical layer The bottom-most layer of the Seven
Layers of Open Systems
Interconnection (OSI) Model is
Physical Layer.
Fast Ethernet,RS232,
and ATM are protocols with physical
layer components.