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The next layer is the third layer of the OSI reference model.

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The network layer.

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The network layer provides the means of transferring variable length network packets from a source to

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a destination host via one or more networks.

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In other words, the network layer is responsible for packet forwarding, including routing through

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intermediate routers.

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Within the service layering semantics of the OSI network architecture.

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The network layer responds to the service requests from the transport layer and issues service requests

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to the data link layer.

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So here are the functions of the network layer.

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Connectionless communication.

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For example, IP is connectionless in that a data packet can travel from a sender to a recipient without

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the recipient having to send an acknowledgement.

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Connection oriented protocols exist at other higher levels of the OSI model.

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Host addressing.

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Every host in the network must have a unique address that determines where it is on the Internet.

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Addresses are known as IP addresses.

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Message forwarding.

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Since many networks are partitioned into subnetworks and then connect to other networks for wide area

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communications networks, use specialized hosts called Gateways or routers to forward packets between

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networks.