IP Address

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IP Address : Internet Protocol Address (or IP Address) is an unique address that computing devices use to identify itself and communicate with other devices in the Internet Protocol network. Any device connected to the IP network must have an unique IP address within its network. An IP address is analogous to a street address or telephone number in that it is used to uniquely identify a network device to deliver mail message, or call ("view") a website. The traditional IP Addresses (IPv4) uses a 32-bit number to represent an IP address, and it defines both network and host address. Due to IPv4 addresses running out, a new version of the IP protocol (IPv6) has been invented to offer virtually limitless number of unique addresses. An IP address is written in "dotted decimal" notation, which is 4 sets of numbers separated by period each set representing 8-bit number ranging from (0-255). An example of IPv4 address is 216.3.128.12, which is the IP address assigned to topwebhosts.org.

An IP address can be either dynamic or static. A static address is one that you configure yourself by editing your computer's network settings. This type of address is rare, and it can create network issues if you use it without a good understanding of TCP/IP. Dynamic addresses are the most common. They're assigned by the Dynamic Host Configuration Protocol (DHCP), a service running on the network. DHCP typically runs on network hardware such as routers or dedicated DHCP servers. Dynamic IP addresses are issued using a leasing system, meaning that the IP address is only active for a limited time. If the lease expires, the computer will automatically request a new lease. Sometimes, this means the computer will get a new IP address, too, especially if the computer was unplugged from the network between leases. This process is usually transparent to the user unless the computer warns about an IP address conflict on the network (two computers with the same IP address). An address conflict is rare, and today's technology typically fixes the problem automatically.

Domain Names
Its basic job is to turn a user-friendly domain name like "howstuffworks.com" into an Internet Protocol (IP) address like 70.42.251.42 that computers use to identify each other on the network. Domain Name Service is an Internet protocol that provides mapping between a computer's numeric address and a human-friendly name that is easy to remember. Take for example the main Stanford webserver -- www.stanford.edu. DNS translates www.stanford.edu into 171.64.14.237.

DNS names are structured in a hierarchtical manner that allows for distributed administration. The highest layer are the Top Level Domain Names. TLDs, as they are often called, are the last portion of a DNS name. So, .edu in the Stanford example is the top level domain. Currently, there are 7 TLDs plus one for each country. The first 3 can be used by anyone while that the last 4 are restricted to those who meet certain qualifications. 1. .org - used by non-profit organizations 2. .net - supposed to only be used by network providers but typically used for more 3. .com - used by commercial organizations 4. .edu - used by four year educational institutions 5. .mil - used by the United States of America Military 6. .int - used by international organizations 7. .gov - used by the United States of America government

For example, when you enter "http://www.howstuffworks.com" in your browser, part of the network connection includes resolving the domain name "howstuffworks.com" into an IP address, like 70.42.251.42, for HowStuffWorks' Web servers. You can always bypass a DNS lookup by entering 70.42.251.42 directly in your browser Typically, when you connect to your home network, Internet service provider (ISP) or WiFi network, the modem or router that assigns your computer's network address also sends some important network configuration information to your computer or mobile device. That configuration includes one or more DNS servers that the device should use when translating DNS names to IP address.

URL
Definition: URL stands for Uniform Resource Locator. A URL is a formatted text string used by Web browsers, email clients and other software to identify a network resource on the Internet. Network resources are files that can be plain Web pages, other text documents, graphics, or programs. URL strings consist of three parts (substrings): 1. network protocol 2. host name or address 3. file or resource location

These substrings are separated by special characters as follows: protocol :// host / location URL Protocol The 'protocol' substring defines a network protocolto be used to access a resource. These strings are short names followed by the three characters '://' (a simple naming convention to denote a protocol definition). Typical URL protocols include http://,ftp://, and mailto://. URL Host The 'host' substring identifies a computer or other network device. Hosts come from standard Internet databases such as DNS and can be names or IP addresses. For example,compnetworking.about.com is the host for this Web page. URL Location The 'location' substring contains a path to one specific network resource on the host. Resources are normally located in a host directory or folder. For example, /od/internetaccessbestuses/bldef-url.htm is the location of this Web page including two subdirectories and the file name. When the location element is omitted such as in http://compnetworking.about.com/, the URL conventionally points to the root directory of the host and often a home page (like 'index.htm').

Intranet
An intranet is a set of Internet services (for example a web server) inside a local network, i.e. only accessible from workstations of a local network, or rather a set of well-defined networks that are invisible (or inaccessible) from the outside. An intranet within an enterprise makes it easy to make a wide variety of different documents available to employees, which provides centralized and coherent access to the enterprise's knowledge, which is referred to as capitalization of knowledge. In this manner, it is generally necessary to define the access rights of the users of the Intranet to the documents located thereon, and consequently authentication of such access rights to provide them with personalized access to certain documents.

Extranet
An extranet is an extension of the information system of the company to its partners located outside of the network. Access to the extranet must be secured to the extent that the same provides access to the information system for persons located outside of the enterprise. This might involve simple authentication (authentication via user name and password) or strong authentication (authentication via a certificate). It is rather a supplementary system providing, for example, the clients of an enterprise, its partners or its subsidiaries with privileged access to certain computer resources of the enterprise via a Web interface.

Network media Twisted pair cables

Twisted pair cable consists of four pairs of wires, each wire is encased in a plastic jacket. The pairs are twisted together to eliminate noise. Its a most common form of cabling found on LANs today. It is relatively inexpensive, flexible, and easy to install and it can span a significant distance. All twisted pair cables fall in to one of twol categories STP and UTP.

STP STP consists of twisted wire pairs that are not only individually insulated but also surrounded by a shielding made of a metallic substance such as foil. It generally uses copper shielding. The shielding acts as a barrier to external electromagnetic forces, thus preventing them from affecting the signals travelling over the wire inside the shielding.

UTP UTP cabling consists of one or more insulated wire pairs encased in a plastic sheath. It does not contain additional shielding for the twisted pairs and both less expensive and less resistant to noise than STP.

Coaxial Cables

Coaxial cables are a type of cable that is used by cable TV and that is common for data communications. Taking a a round cross-section of the cable, one would find a single center solid wire symmetrically surrounded by a braided or foil conductor.
Data is transmitted through the center wire, while the outer braided layer serves as a line to ground. Both of these conductors are parallel and share the same axis. This is why the wire is called coaxial!

Coaxial cabling is the primary type of cabling used by the cable television industry and is also widely used for computer networks, such as Ethernet. Although more expensive than standard telephone wire, it is much less susceptible to interference and can carry much more data.

Fiber Optics
Fiber optics (optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are arranged in bundles called optical cables and used to transmit light signals over long distances. If you look closely at a single optical fiber, you will see that it has the following parts: • • Core - Thin glass center of the fiber where the light travels Cladding - Outer optical material surrounding the core that reflects the light back into the core



Buffer coating - Plastic coating that protects the fiber from damage and moisture Hundreds or thousands of these optical fibers are arranged in bundles in optical cables. The bundles are protected by the cable's outer covering, called a jacket. Optical fibers come in two types:

• •

Single-mode fibers Multi-mode fibers

• SPEED: Fiber optic networks operate at high speeds - up into the gigabits • BANDWIDTH: large carrying capacity • DISTANCE: Signals can be transmitted further without needing to be "refreshed" or strengthened. • RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors or other nearby cables. • MAINTENANCE: Fiber optic cables costs much less to maintain.
Wireless Media radio waves have a longer wavelength than infrared light.Radio waves are used for many things each day, this includes communication, cell phone use, internet, cable television and security alarm systems. Infrared light only functions through line of sight, whereas radio waves can effectively be used from a long distance. A remote control uses infrared light to change the channel on your TV, while radio waves are used to receive TV shows. If you want to communicate through the use of infrared technology, you will not be regulated; however, if you want to operate a radio station, you must obtain a Federal Communications Commission (FCC) license. Although invisible, radio waves are used daily, this includes shortwave radio, aircraft and shipping bands, AM radio, TV and FM radio.

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