WHAT IS OSI STACK ?
The information standard organisation (ISO) developed the open system interconnection model (OSI).
. it is a network model.
. It is a reference model.
. it consists of seven layers and each layer perform a particular network function .
. In this model 1-4 layers are considered the lower layer and layers 5 -7 called the upper layers.
7 LAYER OF OSI MODEL
1. PHYSICAL LAYER:-
. The lowest layer of the OSI reference model is the physical layer.
. this layer represent all the physical devices like computers, transmission media, connecting devices e.t.c.
. it is responsible for the actual physical connection between the devices.
. Physical layers contains information in the form of bits.
. Hub, repeater, modem, cables are physical layer devices.
. It's deal with physical technologics i.e. Bus, star, ring, or mesh.
. Data encoding is also done in this layer.
2. DATA LINK LAYER:-
. the data link layer is responsible for the node to node delivery of the message.
. Switches and bridge data link layer devices.
. This layer is responsible for the error free transfer of data frames.
. It contains two sublayers.
* Logical link control layer (LLC)
* Media access control layer (MAC)
* LOGICAL LINK CONTROL LAYER (LLC):- it defines the address of the network layer protocol from the header.
* MEDIA ACCESS CONTROL LAYER (MAC):-
. It is a link between the LLC and the network layer.
. It controls access to the physical media for transport.
. It is also responsible for the physical addressing of frames.
. Two common MAC layers type include Ethernet and 802.11 wireless specifications.
* FUNCTION OF DATA LINK LAYER:-
1. FRAMING:- the data link layer translate the physical raw bit stream into packets known as frames.
2. PHYSICAL ADDRESSING:- the adds a header to the frame to define the physical address of the sender or receiver of the frame.
3. FRAME CONTROL:- it is the technique through which the constant data rate is maintained on both side so that no data get corrupted.
4. ERROR CONTROL:- it also uses a mechanism to prevent duplication of frames.
5. ACCESS CONTROL:- it provide which of the devices has control over the link at any given time. When two or more devices are connected to the same link.
3. NETWORK LAYER:-
Network layer work for the transmission of data from one host to the other host in different network.
. If two system are connected on the same link there is no need for a network layer.
. It acts as a network controller.
* FUNCTION OF NETWORK LAYER
. Routers and gateways operate in the network layer.
. It translates logical network address into physical machine address.
. It breaks the large packets into a small packets.
. The network layer can support either connection oriented or contain less networks, such as a network can only be of one type and not both.
4. TRANSPORT LAYER:-
. The data is transport layer is referred to as segments.
. it provides a point to point connection between source and destination to deliver the data.
. It is responsible for the end to end delivery of the complete message.
* FUNCTION OF TRANSPORT LAYER
. It divides is messages into packets.
. It performs end to end flow control
. It provide connectionless and connection oriented devices.
. It is also called heart of the OS I model.
. a transmission may be sent or arrive in the form of packets that need to be reconstructed into a complete message at the other end.
5. SESSION LAYER:-
. it manage and synchronise the conversion between two different application.
. it is also responsible for masking potential transport layer from upper layer protocols.
. Examples of session layer protocols include X.225, apple talk and zone information protocol (ZIP).
* FUNCTION OF SESSION LAYER
. It allowed two system to start a dialogue with each other.
. it allow the communication between two process which can be either half duplex or full duplex.
. Manage data synchronisation of multiple session streams.
. Setup tears down and massages the communication between two application end points.
6. PRESENTATION LAYER:-
. It is also called the translation layer or syntax layer.
. It is mainly concerned with the syntax and semantics of the information exchange between the two layer.
. The presentation layer can serialise translate more complex application data objects into a storable and transportable format.
*FUNCTION OF PRESENTATION LAYER
. It translate the data between two formats.
e.g. ASCII TO EBCDIC
. It reduces the number of bits to be translated.
. Insurance propecia formatting and delivery to and from the application layer.
. Perform data encryption.
. Manages segregation of data objects.
7. APPLICATION LAYER:-
. It is also called as desktop layer.
. It is the top layer of OSI model.
. It handles issues such as network transparency, resources allocation e.t.c.
. It provides services for an application program to ensure that effective communication with another application program on a network is possible.
* FUNCTION OF APPLICATION LAYER
. It provide file transfer, access and management (FTAM)
. It provide basis for email forwarding and storage.
. Determines protocol and data syntax rules at the application layer.
. Presents the data on the receiving end to the user application.
BY:- GAUTAM KUMAR PATEL
( TECH2GAUTAM)