Chapter One The Internet is made up of many segments, more than 2 billion end systems are connected to these Internet connections. It means that the Internet is a network of networks. They have to send the Internet to all 2 billion end systems, and a month of Internet can be up to 40 exabytes. This means that one year of the Internet would be 12 * 40 = 480. This means 480 Exabytes per year and one thousand Exabytes = 1 ZB and about every two years there will be an amount of memory of about 1 ZB. Those are so many memories. The path connects all those end systems or so-called "hosts". The Internet is made of protocols. They are very important to the Internet and most of this book talks about them. Distributed applications are also very important, they are email, VoIP, peer to peer, gaming network, all that stuff. If you want to distribute a computer application you must use the Internet to send data. You need to first program it to send the data you use to certain services from the Internet. PROTOCOL is basically a connection between two systems. Like saying hello and the other person says hello and you ask the time and they tell you the time. This way we greet the person and the computer greets a computer and asks for the time and the other computer gives it. A protocol defines the format and order of messages exchanged between two or more communicating entities, as well as the actions taken upon the transmission and/or reception of a message or other event. The other thing is how can Google search transport data so quickly, it's because of the amount of servers it has. Google has around 30-50 data centers and with more than a thousand servers each. 65% of developed countries have access to the Internet at home. The usual way the houses connect... in the center of the layer......of paper provides connections for talking and sending stuff. The session layer needs to have a recovery scheme, demarcation and do other things. THE NETWORK UNDER ATTACK Networks can be under attack, attackers can flood your computer by filling gigantic useless files and crash the host. The other types are worms that can spread easily by sneaking into an email and easily infecting many others. the other is sniffers, they can sniff all the keystrokes you do to access a bank account and they can make your money copy a package you are sending. The last one is to disguise someone you trust as your family and use the trust to deceive you. The History of the Internet In 1960, the first Internet connection was made, the packet switching device was made, years later, the packet circuit was upgraded, and the number of users also increased. End System = Host.