Whenever networks are implemented and different devices try to communicate over the network. Some of the other reference models are being referred to which is a standard specification or framework to provide standardization on how implementation, connectivity, communication will happen. It could be OSI or TCP/IP Model. Both are reference models which means we can take a reference or help from the specification of these two models while designing a network. All reference models follow a layered architecture approach and the same applies to OSI and TCP/IP.

Today we look more in detail about two most popular and widely used reference models – OSI and TCP/IP, their features, functions and use cases.

About TCP/IP model

TCP stands for Transmission Control Program and IP stands for Internet protocol. TCP/IP model has a layered architecture and has four layers. The TCP/IP model is protocol-oriented standard. This model was developed by the Department of Defence (DOD) project agency. Internet protocols are a set of rules defined for communication over the network. TCP/IP is considered the standard model for networking and handles data transmission and IP handles addresses. The TCP/IP suite includes protocols such as TCP, UDP, ARP, DNS, HTTP, ICMP etc.

TCP/IP Model Features

Multi-vendor support is available
Used for around 35 years and most widely used protocol
It supports interoperability
It supports logical addressing
It has routability feature
It has name resolution feature
Error control and flow control are supported features

About OSI Model

The OSI stands for Open System Interconnection, developed in the 1980s by the International standard organization. It is a conceptual model used in network communication. The OSI model consists of seven layers and each layer is connected to each other. The data moves through the OSI model from its start till end (Last layer of OSI model).

OSI Model Features

Model to demonstrate how hardware and software work together
Ease of troubleshooting (Each layer detects and handles error)
Reduction in complexity
Standardization of interfaces
Facilitates modular engineering
Provides interoperability between vendors

The application layer of the TCP/IP model maps to the first three layers i.e., Application, Presentation & Session Layer of the OSI model. The transport layer maps directly to the transport layer of the OSI model. The Internet layer maps to the Network layer of the OSI model. The last two layers of the OSI model map to the Data link layer and physical layer of OSI model. TCP/IP model is more widely used as compared to OSI model.

Similarities between TCP/IP and OSI Model

Common Architecture – both models are logical and have similar architecture based on layered approach.

Defined Standards – both models define the standard and framework for implementing the standards and devices.

Troubleshooting is simplified – by breaking complex functions at each layer into simple components.

Pre-defined standard – the protocols and standards are already pre-defined; and models do not redefine them, it just references it or uses it. Like Ethernet standards were already defined by IEEE before the origin of this model and it uses this in its reference at Physical layer or Network access layer.

Similar functionality at transport and network layer – function performed between presentation and network layer is similar to the function performed at transport layer.

Comparison Table: TCP/IP MODEL vs OSI MODEL

Below table summarizes the differences between the two:

FUNCTION	TCP/IP MODEL	OSI MODEL
Definition	TCP/IP stands for Transmission control protocol/ Internet protocol	OSI stands for Open systems Interconnection
Developed by	It is developed by DOD (Department of Defence) project agency.	OSI model is developed by ISO (International standard organization).
Technology/ Platform	It comprises of a set of standard protocols which lead to development of the Internet. It is a communication medium which provides connection between hosts.	It is an independent standard and generic protocol used as a communication gateway between network and end user.
Delivery of Packets	No guaranteed delivery of packets at transport layer.	Transport layer provides guaranteed delivery of packets.
Approach	Based on horizontal approach.	Based on vertical approach.
Application Layer	Session and presentation layers are not separate, both are included in application layer.	Session and presentation layers are separate
Type of Model	Implemented model of OSI model.	It is a reference model on which various networks are built.
Network layer	Network layer provides only connectionless service.	Network layer provides connection oriented and connection less services (Both)
Replaceable/ Non-replaceable Protocols	Protocols can’t be easily replaceable	In OSI model protocols are hidden and can be easily replaceable when technology changes occur
Number of Layers	Comprises of four layers	It comprises of seven layers
Protocol Dependent/Independent	Services, protocols, and interfaces are not properly segregated but are protocol dependent	Services, protocols and interfaces are defined and it is protocol independent
Usage	Widely used model	Limited usage of the model
Standardization of devices	Do not provide standardization of devices	Standardization of devices like router, switches, load balancers and other hardware devices