DCCN PPTDCCN PPT ON ONOSI REFERNCE(7 OSI REFERNCE(7 LAYER)MODEL LAYER)MODEL
BYBY
Bhargavi and groupBhargavi and group
DECE DECE
An open system is a set of protocols that allow two different systems to communicate regardless of their
Open Systems Interconnection Open Systems Interconnection (OSI) it is a networking model which is fundamental to all communications between network devices
It is now the theoretical model for how communication takes place between network devices.
The OSI reference model is an arbitrary hierarchical stratification (layering) of computer networking functions. The stratification consists of seven layers.
The OSI Reference ModelThe OSI reference model consists of seven layers, not including layer 8, the
end user’s application, and layer 0 the physical transmission media.8. O/S or User Application
0. Physical Transmission Media
THE SEVEN OSI THE SEVEN OSI REFERENCE MODEL REFERENCE MODEL LAYERSLAYERS
LAYER 1: PHYSICALLAYER 1: PHYSICAL The physical layer deals with the physical The physical layer deals with the physical
characteristics of the transmission medium. characteristics of the transmission medium. and it sends the data in the form and it sends the data in the form
of raw bitsof raw bits It defines the electrical, mechanical, It defines the electrical, mechanical,
procedural, and functional specifications for procedural, and functional specifications for activating, maintaining, and deactivating the activating, maintaining, and deactivating the physical link between end systems. physical link between end systems.
. .
FUNCTIONS
It controls the define voltages and bit rates needed for transmission
This layer manages the interface between the computer and the network medium (coaxial cable, twisted pair)
It is the bottom layer of the OSI model
1.Signal encoding1.Signal encoding 2.Bit synchronization2.Bit synchronization 3.transmission type3.transmission type 4.topology4.topology 5.Transmission media5.Transmission media MultiplexingMultiplexing Interface 6. Bandwidth 7.Signal typeInterface 6. Bandwidth 7.Signal type
This layer takes the data frames (or) messages from the layer and provides their actual transmission
A message is a block statement such as ok (or) yes, which denotes positive (or) negative acknowledgement (or) request for repeating such as “come again” (or) pardon me .
At the sending end this layer handles conversion of data into raw formats that can be handled by the Physical Layer
Layer 2 : DATA LAYER
Data Link LayerData Link Layer
synchronizationsynchronization To take packets from the upper layer and To take packets from the upper layer and
converting them into framesconverting them into frames To take bits from lower and converting them into To take bits from lower and converting them into
packetspackets Error detection and controlError detection and control FramingFraming
010110110101
011000101110110000001
DATA LINK LAYER
LAYER 3: NETWORKLAYER 3: NETWORK
Defines end-to-end delivery of packets. Defines end-to-end delivery of packets. It receives the packets from transport It receives the packets from transport
layer and converts them into frameslayer and converts them into frames Defines how routing works and how Defines how routing works and how
routes are learned so that the packets routes are learned so that the packets can be delivered. can be delivered.
It is responsible for sending the data to It is responsible for sending the data to destination node by choosing the data destination node by choosing the data
NETWORK LAYER
Establishing the connection
Releasing the connections
Sending the data
This layer also handles packet switching and network congestion control
LAYER 4: TRANSPORTLAYER 4: TRANSPORT
If once it receives the data from session If once it receives the data from session layer it splits the data into packets layer it splits the data into packets
After dividing it adds sequence to the After dividing it adds sequence to the packetspackets
It is responsible for error control and It is responsible for error control and flow controlflow control
The Transport LayerThe Transport Layer DIAGRAMDIAGRAM
ERROR CONTROL: while transmitting the data if they are errors in the data which is been sent to the destination node it detects and controls the error and resends the data to the node
FLOW CNTROL: when the data is sent . The form of data sending should be maintained currently for acknowledgement
LAYER 5: SESSION LAYERLAYER 5: SESSION LAYER
When once the data is received from the presentation layer it is When once the data is received from the presentation layer it is converted in the form of sessions converted in the form of sessions
Again this sessions are divided into sub sessions Again this sessions are divided into sub sessions It avoids the retransmission by adding the checking point It avoids the retransmission by adding the checking point
feature if the system craches (or) power failures last checking feature if the system craches (or) power failures last checking point substation re-trasnmitts the left data but not the entire point substation re-trasnmitts the left data but not the entire data againdata again
At destination side it receives the data from the transport layer At destination side it receives the data from the transport layer and handovers the data to the presentation layerand handovers the data to the presentation layer
Whenever it is divided into substations it adds the sequence Whenever it is divided into substations it adds the sequence numbernumber
The Session LayerThe Session Layer
Responsibilities:Responsibilities: establishes, manages, and terminates establishes, manages, and terminates
sessions between applications.sessions between applications. service location lookupservice location lookup
Responsible for security and access control to session information (via session participant identification)
Responsible for synchronization services
(checkpoints)
LAYER 6: PRESENTATIONLAYER 6: PRESENTATION
It provides compression of dataIt provides compression of data It is concerned with Semantics and It is concerned with Semantics and
syntax of the informationsyntax of the information Provides compression of dataProvides compression of data It is responsible for It is responsible for Data EncodingData Encoding Data CompressionData Compression Data conversionData conversion
The Presentation LayerThe Presentation Layer
Responsibilities:Responsibilities: data encryptiondata encryption data compressiondata compression data conversiondata conversion
PRESENTATION LAYER
Data Encoding: The data is encoded i.e if one node (source node) supports ASCII format, Destination node may support UNICODE format and at this time the data is transmitted in the form of UNCODE even the source node supports ASCII format
Compression: The data is compressed before sending it to the destination node, here the data is compressed in the destination layer
This layer is also responsible for certain protocol conversions, data encryption/decryption, or data compression/decompression.
The top layer of the OSI model
The container which contains various types of protocols i.e www, http is called application layer
If once it is connected to the protocol it handovers to the presentation layer
LAYER 7: APPLICATIONLAYER 7: APPLICATION
APPLICATION LAYER
The application layer is the closest to the user.The application layer is the closest to the user.
It provides network access to the user. It provides network access to the user. It differs from the other layers in that it does It differs from the other layers in that it does
not provide services to any other OSI layer, not provide services to any other OSI layer, but rather, only to applications outside the OSI but rather, only to applications outside the OSI model. model.
Examples of such applications are spreadsheet Examples of such applications are spreadsheet programs, word processing programs, and programs, word processing programs, and bank terminal programs. bank terminal programs.
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical
Tran
smission M
edia
UserApplication
UserApplication
Sending Computer Receiving Computer
EXAMPLE FOR OSI REFERENCE MODEL FUNCTIONING
Top Related