How Our Customers Communicate With Us Katherine Barrios ISDS 4120 Project 1

Internet Customer Computer 1.2.3.4 Company Computer 5.6.7.8 The Internet is a global network of computers, therefore, each computer connected to the Internet must have a unique address, also known as an IP Address. The picture displayed shows two computers, our customer’s and our company’s, with their unique IP Addresses and the Internet in between. This presentation will further explain how information flows across the internet from the customer’s computer IP Address 1.2.3.4 to our company’s computer IP Address 5.6.7.8

Connectivity In order to connect to the internet, the customer may go through an Internet Service Provider (ISP) or a Local Area Network (LAN). Through an ISP you are usually assigned a temporary IP Address for the duration of your dial-in session, and through the LAN connection, your computer might have a permanent IP Address. Which ever way the customer is connected to the Internet, the computer is given a unique IP Address.

Protocol Layers Protocol Layer Comments Application Layer Protocols specific to applications such as WWW, e-mail, FTP, etc. Transport Layer TCP directs packets to a specific application on a computer using a port number. Network Layer IP directs packets to a specific computer using an IP address Physical Layer Converts binary packet data to network signals and back. (E.g. Ethernet network card, Modem for phone lines, etc.) Once connected to the Internet, in order to communicate on the Internet, every computer needs the the TCP/IP Protocol Stack. These are protocols that are placed throughout each layer of the OSI Model and are each demonstrated throughout the data flow process.

TCP/IP Protocol Application Application TCP TCP IP IP Internet For information to be sent from the customer’s computer to our company’s computer, the data packet will start at the top of the protocol stack, at the Application Layer, on the customer’s computer and work it's way downward towards the Hardware Layer to then be transmitted over the internet. Hardware Hardware Customer Computer 1.2.3.4 Company Computer 5.6.7.8

DNS Domain Names www.company.com https://5.6.7.8 It all begins when the customer types your company’s URL into a browser on his/her own computer at their home. Because most people have trouble remembering the strings of numbers that make up IP addresses, and because IP addresses sometimes need to change, all servers on the Internet also have human-readable names, called domain names. For example, the customer probably typed in “WWW.COMPANY.COM” because it is easier for most of people to remember than a long string of numbers. Because the URL contains the domain name “www.COMPANY.com”, the browser first connects to a domain name server (DNS) and maps the human readable name to the corresponding IP address for the web server.

Application Protocols: HTTP HTTP Request HTTP Response Once the web browser connects to the web server, it sends an HTTP request (via the protocol stack) for the desired web page. The web server receives the request and checks for the desired page. If the page exists, the web server sends it. If the server cannot find the requested page, it will send an HTTP error message. The web browser receives the page back and the connection is closed. The browser then parses through the page and looks for other page elements it needs to complete the web page. These usually include images, applets, etc. For each element needed, the browser makes additional connections and HTTP requests to the server for each element. When the browser has finished loading all images, applets, etc. the page will be completely loaded in the browser window.

Packets If the customer has entered a large amount of data, the info then needs to then be broken down into smaller pieces or packets, called packet switching. Packet switching is when you send an email or browse the Web, the data you send is split up into lots of packets that travel separately over the Internet. This is because data sent over the Internet (and most computer networks) are sent in manageable chunks.

Transport Protocols: TCP The Transmission Control Protocol/Internet Protocol, the Internet's fundamental "control system”, sorts the data that is able to move back and forth between one computer (or IP address) and another. It is the TCP that figures out how to get the data from the source to the destination, arranging for it to be broken into packets, transmitted, resent if they get lost, and reassembled into the correct order at the other end. To accomplish this, port numbers are used. When a packet arrives at a computer and makes its way up the protocol stack, the TCP layer decides which application receives the packet based on a port number. Source Destination

Network Protocol: IP 1.2.3.4 5.6.7.8 SENDER’S ADDRESS RECIPIENT’S ADDRESS 5.6.7.8 Checker DATA After passing through the application layer and the TCP layer, the Network layer finalizes the package as shown above. This layer is where each packet receives it's destination address. It is IP's job is to send and route packets to other computers.

Physical Protocols DATA Now that our packets have a port number and an IP address, they are ready to be sent over the Internet. The hardware layer takes care of turning our packets containing the alphabetic text of our message into electronic signals and transmitting them over the Internet. 1110001010011110001011010100101111100001010010111011100010100111100010110101001011111000010100101110

1110001010011110001011010100101111100001010010111011100010100111100010110101001011111000010100101110 Electronic signals and transmitted over the Internet.

Deputy Router Because the internet is a series of many interconnecting networks, an electronic version of a “traffic cop”, technically known as an internet router, directs the data down the correct internet path to the computer designated in the destination IP Address in the packet (which is the company’s computer).

Arrival Eventually, the packets reach our company’s computer 5.6.7.8

Application Application TCP TCP IP IP Internet Hardware Hardware Here, the packets start at the bottom of our computer's TCP/IP stack, at the hardware layer, and work upwards. As the packets go upwards through the stack, all routing data that the sending computer's stack added (such as IP address and port number) is stripped from the packets. Hardware Hardware Customer Computer 1.2.3.4 Company Computer 5.6.7.8

Hi Company!! Sincerely, the Customer When the data reaches the top of the stack, the packets have been re-assembled into their original form and the message from the customer may be viewed by our company.