The OSI Model is a framework that is used to describe the functions of a networking system. The OSI model characterizes functions into a universal set of rules and requirements to support interoperability between different products and software. In the OSI model, the communications between a system are split into seven distinct layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
The lowest layer of the model is concerned with transmitting raw unstructured data across the network from the device’s physical layer to the receiving device’s physical layer. It includes specifications such as voltages, pin layout, cabling, and radio frequencies. One might find “physical” resources at the physical layer, such as network hubs, cabling, repeaters, network adapters, or modems.
Data Link Layer
The directly connected nodes are used to perform node-to-node data transfer, where data is packaged into frames. It corrects the errors that occur at the physical layer. The first, media access control, provides flow control and multiplexing for device transmissions over a network. The second, the logical link control, provides flow and error control over the physical medium and identifies line protocols.
This layer is responsible for receiving frames from the data link layer and delivering them to their intended destinations based on their addresses. The network layer finds the goal by using logical addresses, such as IP. At this layer, routers are an essential component used to quite literally route information where it needs to go between networks.
This layer manages the delivery and error checking of data packets. It regulates the size, sequencing, and, ultimately, data transfer between systems and hosts.
This layer controls conversations between various computers. A session between machines is set up, managed, and terminated at layer 5. Session layer services include authentication and reconnections.
It translates or formats data based on the syntax or semantics that the application accepts. Because of this, it, at times, is also known as the syntax layer. This layer also handles the encryption and decryption required by the application layer.
At this layer, both the application layer and the end-user interact directly with the software application. This layer sees network services provided to the end-user applications such as a web browser or Office 365. The application layer identifies partners for communication, resource availability and synchronizes transmission.
Characteristics of the OSI Model
- A layer should only be created where definite levels of abstraction are needed.
- The function of every layer must be selected as per the internationally standardized protocols.
- The layers should be large so that the functions should not be put in the same layer.
- In the OSI model, every layer relies on the next layer to perform primitive functions. Each level should be able to provide services to the next higher layer.
- Changes made in one layer must not need changes in other lavers.
- It helps you to standardize switch, router, motherboard, and other hardware
- Reduces complexity and standardizes interfaces
- Facilitates modular engineering
- Allows you to ensure interoperable technology
- Protocols are replaced by new protocols when technology changes.
- It offers support for connection-oriented services as well as connectionless service.
- It supports connectionless and connection-oriented services.
- It provides flexibility to adapt to various types of protocols.
- Fitting of protocols is a tedious task.
- It does not define any specific protocol.
- In the network layer model, some services are duplicated in many layers.
- Layers cannot work in parallel as each layer needs to wait to obtain data from the previous layer.
The TCP/IP model has four layers: application, transport, internet, network access layer. The layers offer physical standards, network interface, internetworking, and transport functions that correspond to the first four layers’ OSI model. These four layers are represented in the TCP/IP model by a single layer called the application layer. TCP/IP is a hierarchical protocol made up of interactive modules, and each of them provides specific functionality.
Network Access Layer
This protocol is used to connect to the host so that the packet can be sent. It varies from host to host and network to network.
The selection of the network is based on a connectionless internetwork layer known as the internet layer. It is the layer that holds the whole architecture together. The order in which packets are received is different from the way they are sent. The functions performed by the Internet Layer are:
- Performing routing
- Delivering IP packets
- Avoiding congestion
It decides whether the data transmission should be on a parallel path or a single path. The transport layer does functions such as multiplexing, segmenting, or splitting into the data. The applications can write and read to the transport layer. The transport layer
An application layer is a topmost layer in the TCP/IP model. It is responsible for high-level handling protocols, issues of representation. It allows the user to interact with the application. When one application layer protocol wants to communicate with another application layer, it forwards its data to the transport layer.
There is an ambiguity in the application layer. Every application cannot be placed inside the application layer except for those who interact with the communication system. For example, a text editor cannot be considered in the application layer. A web browser uses the HTTP protocol to interact with the network where HTTP protocol is an application layer protocol.
adds header information to the data. The transport layer breaks the message (data) into small units to handle more efficiently by the network layer. The transport layer also arranges the packets to be sent in sequence.
Characteristics of the TCP/IP Model
- It supports a flexible architecture
- Adding systems to the network is easy.
- The structure remains intact in TCP/IP until the source and destination machines are functioning correctly.
- TCP is a connection-oriented protocol.
- TCP provides reliability and ensures the data that arrives out of sequence should be put back into order.
- TCP offers you to implement flow control, so the sender never overpowers a receiver with data.
- It helps you to set up a connection between different types of computers.
- It operates independently of the operating system.
- It supports various routing-protocols.
- It enables internetworking between the organizations.
- This model has a highly scalable client-server architecture.
- It is operated independently.
- It supports multiple routing protocols.
- TCP/IP is a complex model to set up and manage.
- The overhead of TCP/IP is higher-than IPX.
- Replacing protocol in TCP/IP is difficult.
- It has no clear separation from its interfaces, services, and protocols.
Difference between OSI vs TCP/IP Model
|OSI Model||TCP/IP Model|
|OSI is a protocol-independent standard, acting as a communication gateway between the network and end-user.||TCP/IP model is based on standard protocols. It is a communication protocol, which allows the connection of hosts over a network.|
|The transport layer ensures the delivery of the packets.||In the TCP/IP model, the transport layer does not guarantee the delivery of packets.|
|Vertical approach.||Horizontal approach.|
|The OSI model has a separate Session layer and Presentation layer.||TCP/IP does not have a separate Session layer or Presentation layer.|
|Transport Layer is Connection Oriented.||Transport Layer is both Connection-Oriented and Connectionless.|
|OSI model around which the networks are built.||TCP/IP model is, in a way, an implementation of the OSI model.|
|Protocols are hidden in this model and can be replaced as the technology changes||Replacing protocol is not easy.|