The international standard organization (ISO) is a multinational body dedicated to a worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection OSI model layers. An open system may be a model that permits any two different systems to speak no matter their underlying architecture. The purpose of the OSI model layers is to open communication between different systems without requiring changes to the logic of the underlying computer hardware and software.

1. OSI model layers | 7 Types
of OSI Model | Edifyclue
The international standard organization (ISO) is a multinational body
dedicated to a worldwide agreement on international standards.
An ISO standard that covers all aspects of network communications is the
Open Systems Interconnection OSI model layers.
An open system may be a model that permits any two different systems to
speak no matter their underlying architecture.
The purpose of the OSI model layers is to open communication between
different systems without requiring changes to the logic of the underlying
computer hardware and software.
The OSI model is not a protocol it is a model for understanding and designing
a data network architecture that is flexible, robust, and interoperable.

2. The Open System Interconnection (OSI model layers) is a framework for
the design of network systems that allow for communication across all types of
computer systems.
It consists of 7 separate but related layers, each of which defines a segment of
the process of moving information across a network.
Function Of The OSI model layers
In this section, we briefly describe the functions of each seven-layer
in the OSI model:-

3. ● Application layer
● Presentation layer
● Session layer
● Transport layer
● Network layer
● Data Link layer
● Physical Layer
Physical Layer:-
The physical layer coordinates the functions needed to transmit a bitstream
over a physical medium. It deals with the mechanical and electrical
specifications of the interface and transmission medium.
It conjointly defines the procedures and functions that physical devices and
interfaces got to perform for transmission to occur. The position of the

4. physical layer is relevant to the transmission medium and also the electrical
circuit layer.
The responsibilities of the physical layer include the following:-
● Physical characteristics of interface and media – The
physical layer defines the characteristics of the interface between
the devices and also the transmission medium.
● Representation of bits:- The physical layer information
incorporates a stream of bits (sequence of 0s and 1s) with no
interpretation. To be transmitted, bits should be encoded into
signals electrical and optical. The physical layer defines the kind
of coding.
● Data rate:- The transmission rate of the number of bits sent
every second is additionally outlined by the physical layer. The
physical layer defines the period of touch, that is however long it
lasts.
● Synchronization of bits:- The sender and receiver should be
synchronous at the bit level. The sender and also the receiver
clocks should be synchronous.
● Line configuration:- The physical layer cares about the
affiliation of devices to the medium. in an exceeding
purpose-to-purpose configuration, 2 devices square measure
connected along through an obsessive link. in an exceedingly
multipoint configuration, a link is shared between many devices.
● Physical topology:- The topology defines however devices
square measure connected to form to network. Devices are often
connected employing a mesh (every device connected to each
alternative device), a topology (devices square measure
connected through central devices), a hoop topology (every
device is connected to successive, forming a ring), or a topology
(every device on a standard link).
● Transmission mode:- The physical layer conjointly defines the
transmission mechanism between 2 devices simplex, half-duplex,
or full-duplex. within the simplex mode, just one device will send
the opposite will solely receive. The simplex mode could be

5. unidirectional communication. within the half-duplex mode, 2
devices will send and receive, however not at the same time. in an
exceedingly full-duplex mode, 2 devices send and receive at
identical times.
Datalink Layer:-
The data link layer transforms the physical layer, a raw transmission facility,
into a reliable link and is responsible for node to node delivery.
It makes the physical layer appear error-free to the upper layer (Network
layer) and the relationship of the data link layer to the network and physical
layers.
The responsibilities of the data link layer include the following:-

6. ● Framing:- the info link layer divides the stream of bits received
from the network layer into manageable data units called frames.
● Physical addressing:- If frames are to be distributed to a
different system on the network, the data link layer adds a header
to the frame to define the physical address of the sender (source
address) and receiver (destination address) of the frame. If the
frame is intended for a system outside the sender network, the
receiver address is the address of the device that connects one
network to the next.
● Flow control:- Data absorbed by the receiver is less than the
rate produced in the sender, the data link layer imposes a flow
control mechanism to prevent massive the receiver.
● Error control:- The data link layer adds reliability to the
physical layer by adding a mechanism to direct and transmit
damaged or lost frames. It also uses a mechanism to stop the
duplication of frames. Error control is generally achieved through
a trailer added to the top of the frame.
● Access control:- When 2 or more devices are connected to an
equivalent link, link-layer protocols are necessary to work out
which device has control over the link at any given time.
Network Layer:-

7. The network layer is responsible for the source to destination delivery of a
packet possibly across multiple network links.
The data link layer oversees the delivery of the packet between 2 systems on
the same network links, and the network later ensures that each packet gets
from its point of origin to its final destination.
If 2 systems are connected to the same link, there is usually no need for a
network layer. If the 2 systems are connected to different network links with
attached devices between the network links, there is often a need for the
network layer to accomplish source-to-destination delivery.
The relationship of the network layer o the data link and transport layer.
The responsibilities of the network layer include the following:-

8. ● Logical addressing:- The physical addressing implemented by
the info link layer handles the addressing problem locally. If a
packet passes the network boundary, we’d like another
addressing system to assist distinguish the source and
destination systems. The network layer adds a header to the
packet coming from the upper layer that, among other things,
involves the logical addresses of the sender and receiver.
● Routing:- When independent networks or links are connected
together to create an internetwork or a large network, the
connecting devices called routers and gateways route the packets
to their final destination. One of the functions of the network
layer is to give this mechanism.
Transport Layer:-

9. The transport layer is accountable for the supply to destination (end-to-end)
delivery of the entire message.
The network layer oversees the finish to complete delivery of individual
packets, it does not acknowledge any relationship between those packets.
It treats all severally as if every bit belonged to a separate message. The
transport layer, on the other hand, ensures that the whole message arrives
intact and then as, overseeing each error management and flow management
at the supply to destination level.
The connection of the transport layer to the network and session layers. The
transport layer mat creates an affiliation between the two finish ports. An
affiliation could be a single logical path between the supply and destination
that go with all packets in a very message.
making an affiliation involves 3 steps: affiliation institution, knowledge
transfer, and affiliation unharness.
Transmission of all packets to 1 pathway, the transport layer has a lot of
management over sequencing, flow, and error detection and correction.
The responsibilities of the transport layer include the following:-
● Service purpose addressing:- Computers usually run many
programs at identical times. supply to destination delivery
suggests that delivery not solely from one pc to the next but
conjointly from a specific method on one pc to a specific method
on the other. The transport layer header so should embody a sort
of address referred to as a service purpose address. The network
layer gets every packet to the correct pc the transport layer gets
the entire message to the correct method on its pc.
● Segmentation and reconstruction:- A message divided into
communicable segments, every phase containing a sequence
variety. These numbers modify the transport layer to put together

10. the message properly upon inward at the destination and to
identify and replace packets that were lost inside the
transmission.
● Connection management:- A connectionless transport layer
treats every phase as AN freelance packet and delivers it to the
transport layer at the destination machine. A
connection-oriented transport layer makes respect to the
transport layer at the destination machine initial before
delivering the packets. in the end, the information is transferred,
and the affiliation is terminated.
● Flow management:- The transport layer is accountable for
flow management. However, flow management at this layer is
performed finish to complete rather than across one link.
● Error management:- The transport layer is accountable for
flow management. However, flow management at this layer is
performed finish to complete rather than across one link. The
causing transport layer makes positive that the entire message
arrives at the receiving transport layer while not an error.
Session layer:-

11. The service provided by the primary three-layer (physical, data link, and
network) is not adequate for a few processes. The session layer is the network
dialog controller. it establishes, maintains, and synchronizes the interaction
between the communication system.
Specific responsibilities of the session layer include the following:-
● Dialog management:- The session layer permits 2 systems to
enter into a dialog. It permits the communication between 2
processes to require place either in half-duplex (one approach at
a time) or full-duplex (two-approach at a time).
Presentation Layer:-

12. The presentation layer is bothered with the syntax and linguistics of the
knowledge changed between the two systems. the connection between the
presentation layer and thus the applying and session layer.
Specific responsibilities of the presentation layer include the
following:-
● Translation:- The method (running program) in 2 systems is
typically exchanging data within the kind of character string,
numbers, and so on. the knowledge ought to be modified to
bitstreams before being transmitted. as a result of totally
different|completely different} computers using different
cryptography systems, the presentation layer is chargeable for
ability between these totally different cryptography ways.

13. The presentation layer at the sender changes the information from its
sender-dependent format into a regular format. the presentation layer at the
receiving machine changes the same format into its receiver-dependent
format.
OSI Model –Wikipedia
● Encryption:- To carry sensitive data, a system should be able to
assure privacy. cryptography implies that the sender transforms
the first data to a different kind and sends that ensuing message
out over the network. cryptography reverses the first method to
rework the messages back to their original kind.
● Compression:- Information compression reduces the amount
of bits t be transmitted. information compression becomes
significantly necessary in the transmission of transmissions like
text, audio, and video.
Application Layer:-

14. The appliance layer allows the user, whether or not human or computer code,
to access the network. It provides user interfaces and support for services like
email correspondence, remote file access and transfer, shared management,
and alternative forms of distributed info services.
Specific services provided by the appliance layer include the
following:-
● Network virtual terminals:- A network virtual terminal may
be a computer code version of a physically terminal and permits a
user to go surfing in a foreign host. the appliance creates a
computer code emulation of a terminal at the remote host. That
user’s laptop talks to the computer code terminal. The remote
host believes it’s a human activity with one amongst its own
terminals and permits you to brand on. File transfer, access, and

15. management (FTAM) – This application permits a user to access
files in an exceedingly remote laptop, and to manage or manage
files in an exceedingly remote laptop.
● Mails services:- This application provides the premise for
email forwarding and storage.
● Directory services:- This application provides distributed info
sources and access to world info regarding varied objects and
services.
Conclusion:-
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