Where does the code for the OSI layer protocols exist?

Question

I know this might sound like a very amateur and stupid question but I don't understand the concepts of these protocols in the OSI model. Are they just code that gets invoked? Also where does this code reside? Is it put on every server machine that needs to conform to the protocol when you are designing the network?

I am reading a book and it states that:

For starters, the abstract objects that make up the layers of a network system are called protocols.

Each protocol defines two different interfaces. First, it defines a service interface to the other objects on the same computer that want to use its communication services.

An implementation of the HTTP protocol could support an operation to fetch a page of hypertext from a remote server.

So in the case of an HTTP protocol when a user hits enter after entering a URL on their browser, some code for the HTTP protocol which is stored on some server machine is being run?

Answer 1

I am reading a book and it states

If I were in a snarkier mood, I'd tell you to burn the book. I'm sure you can find other sources that can explain this more clearly.

A better (and simpler) definition in this context is that a protocol is a set of procedures and objects used for communicating between devices. You might think of it as a specialized language for communication. Each layer uses a specific protocol to talk to the corresponding layer on the other device. For example, IP is the protocol used by the network layer on one device to talk to the network layer on another device. Note that this layer to layer communication is logical.

I don't understand the concepts of these protocols in the OSI model. Are they just code that gets invoked?

Forgetting for a moment that no one actually uses the OSI model, yes the protocols are implemented in code. They are a set of communications functions and data objects. This question and answer might help you better understand.

Is it put on every server machine that needs to conform to the protocol when you are designing the network?

In the case of the TCP/IP model, every device that uses IP has the protocol stack. That includes PCs, servers, routers, etc.

Answer 2

The OSI layer model is a theoretical model used to describe the way that communication among systems had to be handled. A real life communication model is, for example, TCP/IP.

IP is layer 3 and TCP/UDP are layer 4 protocols. Lower layers are managed by WLAN and Ethernet in real life LANs nowadays.

Windows has these layers as software embedded inside the Operating System that can be accessed through Winsock.

On Linux it is part of the kernel. You can check the source code of it here.

HTTP is a server-client protocol.

The HTTP client code is inside the web browser. You can check the source code of Firefox 48 here.

Examples of HTTP servers are Microsoft IIS and Apache. Here is the source code of Apache.

When the user hits enter after entering a URL on his browser( www.google.com for example), then it sends a connection request to the HTTP server. The request goes through the lower layers and then through Internet until it gets to the HTTP server in google.

This HTTP server responds with data that goes through the internet until it gets to the web browser of the user.

Answer 3

The Open Systems Interconnection (OSI) reference model defines a hierarchical conceptual computer networking/communications architecture that is, by and large, obsolete.

The Internet Protocol suite, originally developed by the U.S. Dept. of Defense (DARPA Agency), is the dominant and de facto standard computer networking model in use today. The Internet Engineering Task Force, IETF, is the authoritative body of the Internet Protocol suite.

The World Wide Web (web browsers / websites) adhere to protocol specifications published by the W3C, namely HTML and CSS, and by ECMA International (often simply called JavaScript).

The physical wired and wireless standards fall under the Institute of Electrical and Electronics Engineers, IEEE.