Consider the same example from the previous posts. When you send a message from Vendor 1’s (suppose Apple) device to Vendor 2’s (suppose Samsung) device it succeeds because the rules both the vendors agreed upon.
These rules are defined in networking models. Two important networking models are OSI (Open System Interconnection) reference model and TCP/IP (Transmission Control Protocol / Internet Protocol) protocol suite.
Before going to see OSI vs TCP/IP, we will see both in brief.
OSI vs TCP/IP
OSI Reference Model (Open System Interconnection)
This reference model is for conceptual understanding of rules by the vendors before making the products. It is created by the International Organization for Standardization (ISO).
The open in OSI means that it is open for all the devices to communicate with each other regardless of vendors. It is a model to understand how the data actually flows from one device to another.
It does not have any rules set.
OSI model has 7 layers. Those are as follows.
- Application Layer (Layer 7)
- Presentation Layer (Layer 6)
- Session Layer (Layer 5)
- Transport Layer (Layer 4)
- Network Layer (Layer 3)
- Data Link Layer (Layer 2)
- Physical Layer (Layer 1)
We mostly remember all the layers using “Please Do Not Throw Salami Pizza Away“.
Each individual layer in the OSI model has a different functionality. The layers are generally numbered from the bottoms.
The physical layer is considered as the first layer. It concerns how the ‘data bits’ are transmitted from one device to another.
Data Link Layer concerns about encapsulation of data packet in a frame. It mostly decides based on physical addresses (MAC).
Network layer determines the path using logical (IP) addresses. Routing, device addressing comes under this layer. Protocol IP.
Transport layer segments the data in the chunks (small divisions of data) and combines it again in the receiver. Used for flow control and recovery. TCP and UDP protocols come under this layer.
Session layer manages the session between two devices.
presentation layer does defines the data formats. encryption, decryption come under this layer.
Application Layer is to enable the network applications to communicate with other network applications.
TCP/IP (Transmission Control Protocol / Internet Protocol)
The TCP/IP model is older than the OSI reference model. It was widely used before the later’s introduction. It was created by the Defense Advanced Research Project Agency (DARPA) (United States).
The TCP/IP model has 4 layers only.
- Application Layer (Layer 4)
- Transport Layer (Layer 3)
- Internet Layer (Layer 2)
- Network Access Layer (Layer 1)
The application. presentation and session layer are together forming an application layer here. Also, the physical and data link layer together form the Network access layer.
TCP/IP protocol does not specify much in Network Access Layer.
Internet Layer provides the protocols for the transmission of packets using the best path.
Transport layer defines the protocols like TCP, UDP for data transfer. Responsible for error free communication.
Application layer provides protocols for application level communication between devices.
OSI vs TCP/IP
The major difference between both the network models is the number of layers. While OSI has 7 layers, TCP/IP has only 4.
OSI model is specific about the instructions of data flow in every layer while TCP/IP is not.
OSI model does specify the protocols in each layer thoroghly. TCP/IP does not.
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