Internet Flow By: Terry Hernandez

Getting from the customers computer onto the internet Internet Browser

IP Address When a client wants to go to a specific site they type into the URL the name of where they would like to go. What this does is tell the browser to go to a specific IP address. An IP address is a specific address for everything from your home computer to the name of a website. The reason we name websites things like is because this: is not something as easy to remember. Entering both into the URL however both go to the same place. The router in your house will generally give your computer a IP address every time it goes online automatically. This address is here so after a request is sent out the signal has a return address to come back to. It also will make sure what you request doesn’t go to the computer next to you also on the same network. Each local machine has a NIC or Network Interface Card. This is basically a unique identifier to the system physical address. This is what sends and receives all the data from your computer. Ethernet Addresses AKA MAC(Media Access Control) Addresses are also used here. MAC addresses are usually assigned by the NIC and are stored in its hardware. Some people refer to them as burned in addresses since they don’t change like the IP address does.

OSI Model The OSI model begins with the physical layer. As mentioned earlier the router usually links the physical layer via wireless or a direct wire. The data link layer is next up and at this point data packets are all split up into bits. This is pretty much separating all the data you are sending out into many more manageable little files that get put back together at destination. The network layer is like a post office. It labels everything being sent out so it doesn’t get lost. The Router gives your computer a unique IP address. It routes your messages to the server site it is to go to.

The Transport layer is the layer that makes sure everything goes error free. This layer will also break up messages to even smaller sizes than they already are if necessary to make the trip. Also message acknowledgment happens during this layer. This layer also labels all the broken up pieces that get sent out to ensure they get put back together in the correct order at their destination. Some people refer to part of this layer as the 3 way handshake. What happens is your computer will send a SYN packet to the server. This is sending a request to start a connection. Once at the destination the server will send back a acknowledgment of the request. Finally your computer will acknowledge that it received the acknowledgment and start to transfer data. This data transfer uses ports Ports are like specific doorways will go into one port Data transfer from youtube would use another They are numbered like 80 or 53

Once a customers request data from our server it first gets through the port number. If port number was invalid or bad it never gets to our server. Once through it is in our company’s local network and hits our router. Once verified to be a valid address it comes to the switches. Switches are here to decide where every packet transfer that comes in gets bumped into the correct direction. The switch will read the address out the packet and forward it onto where it needs to go to reach that address.

Now we have reached the Session layer. This is when the clients home computer has connected to our server and both are ready to send data back and forth Now the Presentation layer can begin. During this layer data sent across the network is encrypted and transformed into a format that the next layer the application layer can read it. It helps reduce compatibility problems. Finally we come to the final layer the Application layer. This is the layer we use to communicate with the network. clients, browsers, and FTP are all things we use on the application layer. Anything that involves the user to do something is supported on this layer. So basically the user interface that you physically can see on your computer is here.