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I am a networking student, and I am learning about the OSI system for networks. The concepts for this system are all pretty complicated, but the main issue that I'm having is the main differences between the Networking Layer and the Transportation Layer.

In the video I was learning from (the Comptia Network+ videos on Cybrary), the instructor stated in the Networking Layer video that the main purpose of the Networking Layer is to split data into packets and send it across Networks. In the Transportation video, he says that the Transportation Layer is for creating packets as well. What are the differences between these two layers? I'm very confused, any help would be greatly appreciated.

closed as off-topic by yoonix, Tero Kilkanen, Greg Askew, mdpc, womble Dec 5 '16 at 0:26

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The network layer is responsible for sending packets destined for some other node (or, in some cases several nodes). The packets are sent on a "best effort" principle, i.e. thay are not all guaranteed to reach their destination, or in the same order they were transmitted. The network layer corresponds to the IP layer in the TCP/IP world.

The transport layer builds upon the network layer, and can provide quality of service by providing error control, sequence control, flow control, etc. As a more concrete example, the TCP protocol is considered a transport layer (layer 4) protocol. The TCP segments are transported as payload in IP packets, and, just as the IP packets, consist of a header and a payload.

TCP provides a stream oriented connection between two nodes. To do this the TCP header contains information for the receiver to be able to detect which stream a packet belongs to and which sequence number it has. With this information, the TCP processor can reassemble the received packets in the correct order, and request restransmission of a packet that has been lost in transmit.

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