The third layer of the Open Systems Interconnection (OSI) is called the network layer. While the Data Link Layer functions mostly inside Wide Area Network (WAN) and Local Area Network (LAN), Network Layer handles the responsibility of the transmission of data in different networks.
It has no use on the place where two computers are connected on the same path or link. It has the ability to route signals through different channels and because of that it is considered a network controller. Through this layer, data is sent in form of packets.
The primary responsibilities handled by the Layer are the Logical connection of a setup, routing, delivery error reporting and data forwarding.
Because of it’s functionality and responsibilities, the Network Layer is often seen as the backbone of the entire OSI Model. Hardware devices such as routers, bridges, firewalls, and switches are a part of it with which it creates a logical image of the communication route that can be implemented with a physical medium.
The protocols needed for the functionality of the Network Layer are present in every router and host. Making it one of the most useful of all the layers.
Most known among these protocols are IP (internet protocol), Internetwork Packet Exchange (IPX) and Sequenced Packet Exchange (SPX) or as they are collectively known; IPX/SPX. IPX protocol is also used by the Transport Layer, which alongside the Data Link Layer work with Network Layer as they are placed above and below this layer respectively.
The functions of the Network layer are as follow:
- Translation of logical network address into physical address.
- Service is provided by this layer to the transport layer for sending the data packets to the destination of the request.
- As it consists of Internet Protocol (IP), a connectionless protocol, that is to say it doesn’t need acknowledgement to send transmit data packets, it is capable of forming a connectionless communication, making it the only layer in the model to able to do so. It is also capable of supporting a connection oriented communication like other layers but only one kind of communication can be established at one time.
- It also works as a locator of the IP address from where the data packets was requested from and it also works as a host for that address.
- It is commonly possible for two different subnets to have different address and protocols. That’s Protocols of Network Layer are found in all the router and host so this layer can resolve the issues and provide a common ground for them to form a connection.
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