From the course: Network Programming in C: Develop Reliable Client/Server Applications

View the big network picture - C Tutorial

From the course: Network Programming in C: Develop Reliable Client/Server Applications

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View the big network picture

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- [Instructor] Like everything in technology, networking consists of hardware and software. Both follow specific standards and protocols to ensure that the world keeps network communications active and reliable. The hardware part covers connection technologies such as ethernet, wifi, fiber optic, and so on. The hardware connects computers with routers and gateways. Software on these devices coordinates and manages the network traffic. It's this physical layer that connects the various machines, opening the path for data to be sent back and forth. The software part is where network programming comes in. To make everything work harmoniously, various standards are established. The goal after all is communications. And for that to work, all the parts must understand the same procedures and obey the same protocols. In the late 1970s, the OSI, or Open Systems Interconnect model was developed. It uses seven abstractions or layers to describe the communications process. The physical layer, which is the hardware. Then the data link layer, network layer, transport layer, session layer, presentation layer, and finally the application layer, which is the layer the user encounters. Communications moves in this direction starting with the application and then going through the physical layer over to the other computer where the process reverses itself. The data eventually ending on the recipient or client system's application layer. This model has been replaced with the simplified TCP/IP layer model. Here, you see the two models side by side, which shows how they relate from a historical perspective. Same communications, different protocol. Both start and end with the application layer. In the TCP layer model, you have four layers: network access, internet, host to host, then the process application layer. Network access is the physical layer where the data is transported. The internet layer sends and routes packets of information between the networks. The host to host layer is where a network programming takes place using the various protocols to establish connections and share data. And the process application layer is what's presented to the user such as a web browser or FTP client. As you can imagine, coordinating all this information requires knowledge of the numerous protocols and various procedures, but don't let the specifics in the abstract diagrams overwhelm you. Your focus as a programmer is only on the host to host layer. The other layers handle the details for you, which is the beauty of this layered model. Your job is to make decisions based on the type of data to transfer and then apply the proper protocols to get the job done.

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