OSI Model and Network Layer

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The OSI model is a conceptual model, also known as the seven-layer model, which was established by the International Organization for Standardization (ISO) and the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) to develop commonality in function and interface between communication protocols.

     In Computer network we uses OSI Model used to define how the communication take place between two devices. This model is very popular to understand communication of two computer and troubleshoot the problem if any issue occurs. OSI model uses 7 layer to define the Network communication and its stages to transmit data successfully from Application layer (Data generated) to Physical layer (Data in bits). 


Seven layers of OSI models.

  1. Physical Layer
  2. Data link Layer
  3. Network Layer
  4. Transport Layer
  5. Session Layer
  6. Presentation Layer
  7. Application Layer. 


Each Layer in OSI model defines its own purpose to facilitate successful Network communication. 

The following are some of the advantages of the OSI model:

  • It standardizes the industry and defines what occurs at each layer of the model.

  • By standardizing network components, it allows many vendors to develop products that can interoperates.
  • It breaks the network communication processes into simpler and smaller components, allowing easier development, troubleshooting, and design.
  • Problems in one layer will be isolated to that layer during development, in most cases.

    Protocol is a set of rule that define the how the communication take place between two same or different vendor devices. Usually Protocols are standard define by an organisation that helps to standardize thing before it is available in market to its users. 

    All seven layers in OSI has different category of protocols according to their purpose. On Network layer we have Routing protocols like BGP, OSPF, RIP, EIGRP. All these Routing protocols lies on layer three because layer 3 purpose is to select best network path to reach the destination. So all the protocols which works on Network layer is to either used for best path selection.

Purpose of Network layers 

i. The network layer assigns unique addresses to devices, called logical addresses. 
ii. It encapsulates data from the transport layer into packets.
iii. It forwards packets to network routers, which use algorithms to find the best path for the data.
iv. It uses protocols like the Internet Protocol (IP) to route and address data.
v. It uses the Internet Control Message Protocol (ICMP) to handle errors and diagnostics. 
vi. It uses Quality of Service (QoS) to prioritize certain traffic

Router is Layer 3 device. It works on Layer 3 of OSI model that's the reason we call it L3 device. When different vendor routers connected together then it needs some standard protocols to communicate to make successful delivery of data. Most known vendor of router are like Cisco, Juniper, Arista, HP, Nokia, Huawei, Micortik and many more other vendors who provide these Network layer devices.


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