Internet working Essay

Today, the Internet and World Wide Web (WWW) are familiar terms to millions of people all over the world. Many people depend on applications enabled by the Internet, such as electronic mail and Web access. In addition, the increase in popularity of business applications places additional emphasis on the internet. The Transmission Control Protocol / Internet Protocol (TCP/IP) protocol suite is the engine for the Internet and networks worldwide. Its simplicity and power has lead to be the single network protocol of choice in the world today so the world has become a global village where the people live their life on the Internet. It has no boundaries or barriers, It is open to all who have access to Internet using computer. The e-commerce and online business has really facilitated the people nowadays. The main design goal of TCP/IP was to build an interconnection of networks, referred to as an internetwork, or internet, that provided universal communication services over heterogeneous physical networks. The clear benefit of such an internetwork is the enabling of communication between hosts on different networks, perhaps separated by a large geographical area. 1. Introduction. The internet has been a useful source of information for the public and made things possible which were impossible in the past . Such as emailing has accelerated the process of Mailing and it hardly takes seconds to reach in any part of the world as the Client are connected to Server and the Server connects the clients to world wide web . it is like cob web which keeps connected to all users at the same time . The Internet’s growth has become explosive and it seems impossible to escape the bombardment of www.com’s seen constantly on television, heard on radio, and seen in magazines. Because the Internet has become such a large part of our lives, a good understanding is needed to use this new tool most effectively. This whitepaper explains the underlying infrastructure and technologies that make the Internet work. It does not go into great depth, but covers enough of each area to give a basic understanding of the concepts involved. For any unanswered questions, a list of resources is provided at the end of the paper. Any comments, suggestions, questions, etc.are encouraged and may be directed to the author at the email address given above. The Internet Frame Work As the Internet is a global network of computers each computer connected to the Internet must have a unique address. Internet addresses are in the form nnn. nnn. nnn. nnn where nun must be a number from 0 – 255. This address is known as an IP address. (IP stands for Internet Protocol; more on this later. ) The picture below illustrates two computers connected to the Internet; your computer with IP address 1. 2. 3. 4 and another computer with IP address 5. 6. 7. 8. The Internet is represented as an abstract object in-between. (As this paper progresses, the Internet portion of Diagram 1 will be explained and redrawn several times as the details of the Internet are exposed. ) Diagram 1. a These IP addresses are actually divided into different classes, where each class has it’s own range and criteria to define the number of hosts and networks. These types of information depends on your network size, criteria and purpose. In the Diagram 1. b, you can find the detail information related with the IP address classes. Diagram 1. b. The decimal representation of Internet addresses If you connect to the Internet through an Internet Service Provider (ISP), you are usually assigned a temporary IP address for the duration of your dial-in session. If you connect to the Internet from a local area network (LAN) your computer might have a permanent IP address or it might obtain a temporary one from a DHCP (Dynamic Host Configuration Protocol) server. In any case, if you are connected to the Internet, your computer has a unique IP address. Hierarchical Versus Flat Address Space Internetwork address space typically takes one of two forms: hierarchical address space or flat address space. A hierarchical address space is organized into numerous subgroups, each successively narrowing an address until it points to a single device (in a manner similar to street addresses). A flat address space is organized into a single group (in a manner similar to U. S. Social Security numbers). Hierarchical addressing offers certain advantages over flat-addressing schemes. Address sorting and recall is simplified through the use of comparison operations. Ireland, for example, in a street address eliminates any other country as a possible location. Fig. 1. 1. Hierarchical and flat address spaces differ in comparison operations. Fig: 1. 2 Source: TCP/IP Illustrated, Volume 1, The Protocols. W. Richard Stevens. Addison-Wesley, Reading, Massachusetts. 1994. The Ping Program If any body who is using Microsoft Windows or a flavor of UNIX and have a connection to the Internet, there is a handy program to see if a computer on the Internet is alive. It is called ping, probably after the sound made by older submarine sonar systems. 1 if you are using Windows, start a command prompt window. If you are using a flavor of UNIX, get to a command prompt. Type ping www. yahoo. com. The ping program will send a ‘ping’ (actually an ICMP (Internet Control Message Protocol) echo request message) to the named computer. The pinged computer will respond with a reply. The ping program will count the time expired until the reply comes back (if it does). Also, if you enter a domain name (i. e. www. yahoo. com) instead of an IP address, ping will resolve the domain name and display the computer’s IP address. More on domain names and address resolution later. Protocol Stacks and Packets So your computer is connected to the Internet and has a unique address. How does it ‘talk’ to other computers connected to the Internet? An example should serve here: Let us say your IP address is 1. 2. 3. 4 and you want to send a message to the computer 5. 6. 7. 8. The message you want to send is â€Å"Hello computer 5. 6. 7. 8! † Obviously, the message must be transmitted over whatever kind of wire connects your computer to the Internet. Let us say you have dialed into your ISP from home and the message must be transmitted over the phone line. Therefore the message must be translated from alphabetic text into electronic signals, transmitted over the Internet, and then translated back into alphabetic text. Now there is the question that how is this accomplished? Through the use of a protocol stack. Every computer needs one to communicate on the Internet and it is usually built into the computer’s operating system (i. e. Windows, UNIX, etc. ). The protocol stack used on the Internet is referred to as the TCP/IP protocol stack because of the two major communication protocols used. The TCP/IP stack looks like this: Protocol Layer: Application Protocols Layer Protocols specific to applications such as WWW, e-mail, FTP, etc. Transmission Control Protocol Layer TCP directs packets to a specific application on a computer using a port number. Internet Protocol Layer. IP directs packets to a specific computer using an IP address. Hardware Layer Converts binary packet data to network signals and back. (E. g. Ethernet network card, modem for phone lines, etc. ) If we were to follow the path that the message â€Å"Hello computer 5. 6. 7. 8! † took from our computer to the computer with IP address 5. 6. 7. 8, it would happen something like this: Diagram 2 The message would start at the top of the protocol stack on your computer and work its way downward. If the message to be sent is long, each stack layer that the message passes through may break the message up into smaller chunks of data. This is because data sent over the Internet (and most computer networks) are sent in manageable chunks. On the Internet, these chunks of data are known as packets. The packets would go through the Application Layer and continue to the TCP layer. Each packet is assigned a port number. Ports will be explained later, but suffice to say that many programs may be using the TCP/IP stack and sending messages. We need to know which program on the destination computer needs to receive the message because it will be listening on a specific port. After going through the TCP layer, the packets proceed to the IP layer. This is where each packet receives its destination address, 5. 6. 7. 8. Now that our message 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 phone line. On the other end of the phone line your ISP has a direct connection to the Internet. The ISPs router examines the destination address in each packet and determines where to send it. Often, the packet’s next stop is another router. More on routers and Internet infrastructure later. Eventually, the packets reach computer 5. 6. 7. 8. Here, the packets start at the bottom of the destination computer’s TCP/IP stack 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. When the data reaches the top of the stack, the packets have been re-assembled into their original form, â€Å"Hello computer 5. 6. 7. 8! † Networking Infrastructure: So now you know how packets travel from one computer to another over the Internet. But what is in-between? What actually makes up the Internet? Let us look at another diagram: Diagram 3. 1 Here we see Diagram 1 redrawn with more detail. The physical connection through the phone network to the Internet Service Provider might have been easy to guess, but beyond that might bear some explanation. The ISP maintains a pool of modems for their dial-in customers. This is managed by some form of computer (usually a dedicated one) which controls data flow from the modem pool to a backbone or dedicated line router. This setup may be referred to as a port server, as it ‘serves’ access to the network. Billing and usage information is usually collected here as well. After your packets traverse the phone network and your ISP’s local equipment, they are routed onto the ISP’s backbone or a backbone the ISP buys bandwidth from. From here the packets will usually journey through several routers and over several backbones, dedicated lines, and other networks until they find their destination, the computer with address 5. 6. 7. 8. But wouldn’t it would be nice if we knew the exact route our packets were taking over the Internet? As it turns out, there is a way†¦ The Trace route Program: If you’re using Microsoft Windows or a flavor of UNIX and have a connection to the Internet, here is another handy Internet program. This one is called trace route and it shows the path your packets are taking to a given Internet destination. Like ping, you must use trace route from a command prompt. In Windows, use tracer www. yahoo. com. From a UNIX prompt, type trace route www. yahoo. com. Like ping, you may also enter IP addresses instead of domain names. Trace route will print out a list of all the routers, computers, and any other Internet entities that your packets must travel through to get to their destination. If you use trace route, you’ll notice that your packets must travel through many things to get to their destination. Most have long names such as sjc2-core1-h2-0-0. atlas. digex. net and fddi0-0. br4. SJC. globalcenter. net. These are Internet routers that decide where to send your packets. Several routers are shown in Diagram 3. 1, but only a few. Diagram 3. 1 is meant to show a simple network structure. The Internet is much more complex.