Overview The Internet was developed to provide a communication ...

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|[|Overview |
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|]| | | |The Internet was developed to provide a communication |
| |network that could continue to function in wartime. |
| |Although the Internet has evolved in ways very different |
| |from those imagined by its architects, it is still based on|
| |the TCP/IP protocol suite. The design of TCP/IP is ideal |
| |for the decentralized and robust network that is the |
| |Internet. Many protocols used today were designed using the|
| |four-layer TCP/IP model. |
| |It is useful to know both the TCP/IP and OSI networking |
| |models. Each model offers its own structure for explaining |
| |how a network works but there is much overlap between the |
| |two. Without an understanding of both, a system |
| |administrator may not have sufficient insight into why a |
| |network functions the way it does. |
| |Any device on the Internet that wants to communicate with |
| |other Internet devices must have a unique identifier. The |
| |identifier is known as the IP address because routers use a|
| |layer three protocol, the IP protocol, to find the best |
| |route to that device. IPv4, the current version of IP, was |
| |designed before there was a large demand for addresses. |
| |Explosive growth of the Internet has threatened to deplete |
| |the supply of IP addresses. Subnetting, Network Address |
| |Translation (NAT) and private addressing are used to extend|
| |IP addressing without exhausting the supply. Another |
| |version of IP known as IPv6 improves on the current version|
| |providing a much larger address space, integrating or |
| |eliminating the methods used to work with the shortcomings |
| |of IPv4. |
| |In addition to the physical MAC address, each computer |
| |needs a unique IP address, sometimes called logical |
| |address, to be part of the Internet. There are several |
| |methods of assigning an IP address to a device. Some |
| |devices always have a static address, while others have a |
| |temporary address assigned to them every time they connect |
| |to the network. When a dynamically assigned IP address is |
| |needed, the device can obtain it using several methods. |
| |For efficient routing to occur between devices, other |
| |issues must be resolved. For example, duplicate IP |
| |addresses can stop efficient routing of data. |
| |Students completing this module should be able to: |
| |Explain why the Internet was developed and how TCP/IP fits |
| |the design of the Internet. |
| |List the four layers of the TCP/IP model. |
| |Describe the functions of each layer of the TCP/IP model. |
| |Compare the OSI model and the TCP/IP model. |
| |Describe the function and structure of IP addresses. |
| |Understand why subnetting is necessary. |
| |Explain the difference between public and private |
| |addressing. |
| |Understand the function of reserved IP addresses. |
| |Explain the use of static and dynamic addressing for a |
| |device. |
| |Understand how dynamic addressing can be done using RARP, |
| |BootP and DHCP. |
| |Use ARP to obtain the MAC address to send a packet to |
| |another device. |
| |Understand the issues related to addressing between |
| |networks. |
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|[|9.1|[|Introduction to TCP/IP | |
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| |9.1|[|History and future of TCP/IP | |
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| | |]| | | | |The U.S. Department of Defense (DoD) created the TCP/IP |
| |reference model because it wanted a network that could |
| |survive any conditions. [pic]To illustrate further, imagine|
| |a world, crossed by multiple cable runs, wires, microwaves,|
| |optical fibers, and satellite links. Then imagine a need |
| |for data to be transmitted without regard for the condition|
| |of any particular node or network. The DoD required |
| |reliable data transmission to any destination on the |
| |network under any circumstance. The creation of the TCP/IP |
| |model helped to solve this difficult design problem. The |
| |TCP/IP model has since become the standard on which the |
| |Internet is based. |
| |In reading about the layers of the TCP/IP model layers, |
| |keep in mind the original intent of the Internet. |
| |Remembering the intent will help reduce confusion. The |
| |TCP/IP model has four layers: the application layer, |
| |transport layer, Internet layer, and the network access |
| |layer. Some of the layers in the TCP/IP model have the same|
| |name as layers in the OSI model. It is critical not to |
| |confuse the layer functions of the two models because the |
| |layers include different functions in each model. |
| |The present version of TCP/IP was standardized in September|
| |of 1981. As shown in Figure [pic], IPv4 addresses are 32 |
| |bits long, written in dotted decimal, and separated by |
| |periods. IPv6 addresses are 128 bits long, written in |
| |hexadecimal, and separated by colons. Colons separate |
| |16-bit fields. Leading zeros can be omitted in each field |
| |as can be seen in the Figure [pic]where the field :0003: is|
| |written :3:. In 1992 the standardization of a new |
| |generation of IP, often called IPng, was supported by the |
| |Internet Engineering Task Force (IETF). IPng is now known |
| |as IPv6. IPv6 has not gained wide implementation, but it |
| |has been released by most vendors of networking equipment |
| |and will eventually become the dominant standard. |
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| |[pic]Web Links |
| |History of the Internet |
| |http://www.itep.co.ae/itportal/english/ |
| |Content/EducationalCenter/ InternetConcepts/ |
| |history_future.asp |
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| | | [pic] [pic] |[|9.1|[|Introduction to TCP/IP | |
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| |9.1|[|Application layer | |
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| | |]| | | | |The application layer of the TCP/IP model handles |
| |high-level protocols, issues of representation, encoding, |
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