Layer 7: ApplicationThis is the layer the user is interacting with (software). This can be skype, chrome etc.

Layer 6: PresentationThis is the OS.

Layer 5: SessionThis layer deals with communication between two devices. For example: when the user goes to a website, the user’s computer must open a session between itself and server hosting the website, thus allowing the user to receive the website in the first place. The same goes for any sort of communication, ie VOIP etc.

Layer 4: TransportThis layer deals how much information is sent back and forth in a session. Using the website example it handles the information the user sends in a request, and then the information the server has to retrieve and send back in order for you to see the website.

Layer 3: NetworkThis is where routers operate. Anything regarding the TCP/IP protocol happens here. Think IP’s, subnet masks, default gateways etc.

Layer 2: Data LinkThis is where switches operate.

Layer 1: PhysicalThis is the physical stuff connecting computers together (cables, switches, routers, modems etc etc).

APPLICATION WebBrowser

A web browser such as Internet Explorer or Netscape provides the means for your computer to contact a web server and download several files that go together to produce a single web page.

You can request a web page by typing in a web address (a URL) or by clicking a link in an open web page. The web browser is an APPLICATION. The web browser application gives you the means to select a web server, contact the server and request a web page. The web browser handles the process of finding the web server (the remote computer that has the web page you want stored on it) , requesting the desired web page and displaying all the files contained within the web page.

PRESENTATION  HTTP

The web browser handles PRESENTATION of the web page to the user by converting the files stored at the web server into formats used to display them on your computer.

Your web browser supports varous text formats (UNICODE and ASCII), image file formats (JPG, GIF, PNG, BMP), audio file formats (WAV, MP3, AIFF) as well as Hypertext Markup

Language (HTML) and one or more scripting languages (JavaScript, JScript, VBScript). Conversion of data from one format to another is the job of the PRESENTATION layer. A web browser can convert these file formats into the local formats used on the local computer for displaying images, playing sounds and displaying text; if it cannot, it often can launch an application which does understand the format. Much of the PRESENTATION layer conversions are handled in the program you're running.

SESSION

When you request a web page, a the web browser opens a TCP connection to the web server. The web server sends back the web page and closes the connection. Your web browser then parses the HTML of the web page. Within the web page are instructions written in HTML tags which tell the browser where to find additional files to be displayed within the web page such as style sheets, sound files, images, movies, Flash files and applets. Your web browser automatically opens additional TCP connections to the web server. Each TCP connection is a SESSION.

TRANSPORT TCP

To communicate with a web server your computer must open a TCP connection to the web server and request a web page. The TCP connection breaks up theweb page into managable chunks, lables them with numbers so they can be reassembled in the correct order and TRANSPORTS the pieces across the correct SESSION.

NETWORK IP ARP

Internet Protocol (IP) is a NETWORK layer protocol that uses unique addresses for the web server and for your computer. IP provides the means for your computer to determine whether the web server is a local computer or a computer located somewhere on the Internet. To reach a web server on the Internet, IP protocol also allows your computer to figure out how to reach the Internet web server via your default gateway. Your computer creates a message addressed to the web server with your computer's return IP address. Your computer uses ARP to figure out the physical MAC address of the default gateway and then passes the data to the NETWORK layer.

DATA LINK ETHERNET LLC

Once the request from your web browser has been created it is sent to the network card. Once it reaches your network card it must be converted into a message that is sent from your computer to the default gateway which will forward the message to the Internet. At the DATA LINK layer, the web request is inserted inside a network request to the default gateway.

MACPHYSICAL CSMA/CD

The physical layer provides the means to transmit the web page request to the default gateway.

Illustration with Images Text

Application Layer: Provides network services to user applications. It is responsible for exchanging information between programs running on the machine, such as an e-mail program, and other services running on a network, such as a print server or another computers' application.

Presentation Layer: Concerned with how data is converted and formatted for data transfer. Examples of format conversions include ASCII text for documents and .gif and JPG for images. This layer performs code conversion, data translation, compression and encryption.

Session Layer: Determines how two devices establish, maintain and manage a connection - how they talk to each other. These connections are called sessions.

Transport Layer: Responsible for breaking the data into segments, establishing an end-to-end logical connection between machines, and providing for error handling.

Network Layer:  Responsible for determining addressing on the network, determining the routes that information will take on its journey, and managing network traffic congestion. Data at this level is packaged into packets.

Data Link Layer: Provides the link for how data, packaged into frames is communicated through hardware to be transported across a medium. It communicates with network cards, manages physical layer communications between connecting systems and handles error notification.

Physical Layer: Specifies how data is processed into bits and physically transferred over medium, such as cables. It's responsible for activating and maintaining the physical link between systems.