What are the 7 layers of the OSI model and their function ?
ISO - OSI Model in Communication Networks
ISO stands for International organization of Standardization. This is called a model for Open System Interconnection (OSI) and is normally called as OSI model.
The ISO-OSI model consists of seven layer architecture. It defines seven layers or levels in a complete communication system.
Lets know the features of OSI Model :
Functions of Different Layers are described as follows :-
This layer activates, maintain and deactivate the physical connection. This layer is responsible for :-
ISO stands for International organization of Standardization. This is called a model for Open System Interconnection (OSI) and is normally called as OSI model.
The ISO-OSI model consists of seven layer architecture. It defines seven layers or levels in a complete communication system.
Lets know the features of OSI Model :
- OSI model enables us to easily understand the big picture of network.
- Through OSI models we can understand how hardware and software work together.
- Through OSI models we can understand new technologies as they are developed.
- Through OSI models troubleshooting is easier by separate networks.
- Through OSI models can be used to compare basic functional relationships on different networks.
Functions of Different Layers are described as follows :-
Layer 1: The Physical Layer |
---|
- Movements of individual bits from one node to next.
- Physical characteristics of interface and medium.
- Representation of bits.
- Data rate.
- Synchronization of bits.
- Line configuration.
- Physical topology.
- Transmission mode.
Layer 2: Data Link Layer |
---|
- Moving frames from one node to next (node to node delivery).
- Framing
- Physical addressing
- Flow and error control
- Access control : when two or more devices are connected to the same link, this layer protocols are necessary to determine which device has control over the link at any given time.
Layer 3: Data Link Layer |
---|
- Source to destination delivery of individual packet.
- Logical addressing.
- Routing : by which route data should take.
- Congestion control : controls the traffic of the network
- Billing.
Layer 4: Data Link Layer |
---|
- This layer is responsible for Process to Process delivery of entire message.
- Ensures that whole message arrives intact and in-order.
- Overseeing both Error Control and Flow Control.
- This layer is responsible for Segmentation and Reassembly.
The transport layer can be either Connection Less or Connection Oriented.
A connection less transport layer treats each segment as in independent packet and delivers it to the transport layer at the destination machine.
A connection oriented transport layer makes a connection with the transport layer at the destination machine first before delivering the packets. After all data are transmitted, the connection is terminated.
Layer 5: Data Link Layer |
---|
- Responsible for dialog control and synchronization.
- It establishes, maintains and synchronizes the interaction amongst communication systems.
Layer 6: Data Link Layer |
---|
- Responsible for translation,
- compression and
- encryption.
Layer 7: Data Link Layer |
---|
- Enables the users (whether human or software) to access the network.
- It provides user interface and supports for services such as e-mail, remote file access & transfer, shared database management etc.
- Manipulation of data (information) in various ways is done in this layer.
- Transferring of files disturbing the results to the user is also done in this layer.
Merits of OSI reference model:
- OSI model distinguish between the services, interfaces and protocols.
- Protocols of OSI model are very well hidden.
- They can be replaced by new protocols as technology changes.
- Supports connection oriented as well as connectionless service.
Demerits of OSI reference model:
- Model was devised before the invention of protocols.
- Fitting of protocols is tedious task.
Must Read This Also… TCP/ IP Model (TCP/ IP Protocol Suite)
No comments: