What is the network layer?

• It is the 3rd Layer in OSI. OSI model.
• It manages service requests received from the transport layer, and forwards the requests to the layer of data.
• The network layer transforms physical addresses from logical addresses to
• It determines the path from the point of origin to the destination. It handles traffic issues like switching, routing, and controlling the data packets' congestion.
• The primary function of the layer on top is to transfer the packets from host to host to the host receiving the packets.

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The primary tasks that the network layer performs include:

• Routing: If a particular packet arrives at an input connection on the router's the router will forward the packets to the router's output. For instance, a packet that goes from S1 to R1 is to be sent onto the router along the route to S2.
• Logical Addressing The data link layer handles physical addressing while the network layer is responsible for implementing the logical addresses. Logical addressing can also be utilized to differentiate between the sources and destinations systems. The network layer is an additional header in the packet, which contains the logical address for both sender as well as the receiver.
• Internetworking It is the primary purpose of the layer of network that is responsible for ensuring the necessary connection between various kinds of networks.
• Fragmentation: It is the process of breaking down the packets down into the smallest of single data units that can be traveled through various networks.

Forwarding and Routing

In the network layer, routers used to transmit the packets. Each router has forwarding tables. A router forwards a particular packet by scrutinizing a packet's head field, and then using the value of the header field to calculate the index to the table that forwards. The value that is stored in the forwarding table that is corresponding to the value of the header field is the router's outgoing interface link over where the packet is going to be sent.

For instance, a router that has the header field value 0111 will arrive at the router, and the router indexes this value to the forwarding table to determine the output link's interface 2. The router forwards the signal onto the 2 interface. The routing algorithm decides on the values to be included into the forwarding tables. The routing algorithm may be centralized or distributed.

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Services offered through the Network Layer

• The Guaranteed Delivery Layer gives the guarantee that the packet will be delivered at the destination it was intended for.
• Delivered with guaranteed delivery and bounded delay This service assures that the package can be sent within the defined host-to-host delay.
• In-Order packages This ensures that the package arrives at the location in the exact order they were delivered.
• Guaranteed maximum jitter: This program ensures that the time that is required between two successive messages from the sender equal to the amount of time between their arrival of the final destination.
• Security services The network layer offers security via an encryption key that is shared between the host that is receiving the data and the one that is sending it to. The network layer of the host that is the source encrypted payloads of datagrams that are delivered to the host that is the destination. The network layer on the host that is to be visited would be able to decrypt that payload. In this manner the network layer ensures the integrity of data as well as the authentication of the source.