1.1 LEARNING OBJECTIVES 
1.2 HISTORY OF INTERNET
After going through this unit, you will be able to:
• Know the evloution of Internet.
• Understand the working of the Internet.
• Understand Domain Name System.
• Understand the addressing scheme in the Internet.
• Know the different versions of IP.
• Know the working of an ISP.
• Differentiate www with the Internet.
1.2 HISTORY OF INTERNET
The Internet was the result of some visionary thinking by people in the early 1960s who saw
great potential value in allowing computers to share information on research and development in
scientific and military fields. J.C.R. Licklider of MIT first proposed a global network of
computers in 1962, and moved over to the Defense Advanced Research Projects Agency
(DARPA) in late 1962 to head the work to develop it1. Leonard Kleinrock of MIT and later
UCLA developed the theory of packet switching, which was to form the basis of Internet
connections. Lawrence Roberts of MIT connected a Massachusetts computer with a California
computer in 1965 over dial-up telephone lines. It showed the feasibility of wide area networking,
but also showed that the telephone line's circuit switching was inadequate. Kleinrock's packet
switching theory was confirmed. Roberts moved over to DARPA in 1966 and developed his plan
for ARPANET. These visionaries and many more left unnamed here are the real founders of the
Internet.
The Internet, then known as ARPANET, was brought online in 1969 under a contract let by the renamed Advanced Research Projects Agency (ARPA) which initially connected four major computers at universities in the southwestern US (UCLA, Stanford Research Institute, UCSB, and the University of Utah). The contract was carried out by BBN of Cambridge, MA under Bob Kahn and went online in December 1969. By June 1970, MIT, Harvard, BBN, and Systems Development Corp (SDC) in Santa Monica, Cal. were added. By January 1971, Stanford, MIT's Lincoln Labs, Carnegie-Mellon, and Case-Western Reserve U were added. In months to come, NASA/Ames, Mitre, Burroughs, RAND, and the U of Illinois plugged in. After that, there were far too many to keep listing here. The Internet was designed to provide a communications network that would work even if some of the major sites were down. If the most direct route was not available, routers would direct traffic around the network via alternate routes. The early Internet was used by computer experts, engineers, scientists, and librarians. There was nothing friendly about it. There were no home or office personal computers in those days, and anyone who used it, whether a computer professional or an engineer or scientist or librarian, had to learn to use a very complex system.
E-mail was adapted for ARPANET by Ray Tomlinson of BBN in 1972. He picked the @ symbol from the available symbols on his teletype to link the username and address. The telnet protocol, enabling logging on to a remote computer, was published as a Request for Comments (RFC) in 1972. RFC's are a means of sharing developmental work throughout community. The ftp protocol, enabling file transfers between Internet sites, was published as an RFC in 1973, and from then on RFC's were available electronically to anyone who had use of the ftp protocol.
Libraries began automating and networking their catalogs in the late 1960s independent from ARPA. The visionary Frederick G. Kilgour of the Ohio College Library Center (now OCLC, Inc.) led networking of Ohio libraries during the '60s and '70s. In the mid 1970s more regional consortia from New England, the Southwest states, and the Middle Atlantic states, etc., joined with Ohio to form a national, later international, network. Automated catalogs, not very userfriendly at first, became available to the world, first through telnet or the awkward IBM variant TN3270 and only many years later, through the web. See The History of OCLC The Internet matured in the 70's as a result of the TCP/IP architecture first proposed by Bob Kahn at BBN and further developed by Kahn and Vint Cerf at Stanford and others throughout the 70's. It was adopted by the Defense Department in 1980 replacing the earlier Network Control Protocol (NCP) and universally adopted by 1983.
The Unix to Unix Copy Protocol (UUCP) was invented in 1978 at Bell Labs. Usenet was started
in 1979 based on UUCP. Newsgroups, which are discussion groups focusing on a topic, followed, providing a means of exchanging information throughout the world . While Usenet is not considered as part of the Internet, since it does not share the use of TCP/IP, it linked unix systems around the world, and many Internet sites took advantage of the availability of newsgroups. It was a significant part of the community building that took place on the networks. Similarly, BITNET (Because It's Time Network) connected IBM mainframes around the educational community and the world to provide mail services beginning in 1981. Listserv software was developed for this network and later others. Gateways were developed to connect BITNET with the Internet and allowed exchange of e-mail, particularly for e-mail discussion lists. These listservs and other forms of e-mail discussion lists formed another major element in the community building that was taking place.
In 1986, the National Science Foundation funded NSFNet as a cross country 56 Kbps backbone for the Internet. They maintained their sponsorship for nearly a decade, setting rules for its noncommercial government and research uses.
As the commands for e-mail, FTP, and telnet were standardized, it became a lot easier for nontechnical people to learn to use the nets. It was not easy by today's standards by any means, but it did open up use of the Internet to many more people in universities in particular. Other departments besides the libraries, computer, physics, and engineering departments found ways to make good use of the nets--to communicate with colleagues around the world and to share files and resources.
While the number of sites on the Internet was small, it was fairly easy to keep track of the resources of interest that were available. But as more and more universities and organizationsand their libraries- connected, the Internet became harder and harder to track. There was more and more need for tools to index the resources that were available. The first effort, other than library catalogs, to index the Internet was created in 1989, as Peter Deutsch and Alan Emtage, students at McGill University in Montreal, created an archiver for ftp sites, which they named Archie. This software would periodically reach out to all known openly available ftp sites, list their files, and build a searchable index of the software. The commands to search Archie were unix commands, and it took some knowledge of unix to use it to its full capability.
At about the same time, Brewster Kahle, then at Thinking Machines, Corp. developed his Wide Area Information Server (WAIS), which would index the full text of files in a database and allow searches of the files. There were several versions with varying degrees of complexity and capability developed, but the simplest of these were made available to everyone on the nets. At its peak, Thinking Machines maintained pointers to over 600 databases around the world which had been indexed by WAIS. They included such things as the full set of Usenet Frequently Asked Questions files, the full documentation of working papers such as RFC's by those developing the Internet's standards, and much more. Like Archie, its interface was far from intuitive, and it took some effort to learn to use it well.
Peter Scott of the University of Saskatchewan, recognizing the need to bring together information about all the telnet-accessible library catalogs on the web, as well as other telnet resources, brought out his Hytelnet catalog in 1990. It gave a single place to get information about library catalogs and other telnet resources and how to use them. He maintained it for years, and added HyWebCat in 1997 to provide information on web-based catalogs.
In 1991, the first really friendly interface to the Internet was developed at the University of Minnesota. The University wanted to develop a simple menu system to access files and information on campus through their local network. A debate followed between mainframe adherents and those who believed in smaller systems with client-server architecture. The mainframe adherents "won" the debate initially, but since the client-server advocates said they could put up a prototype very quickly, they were given the go-ahead to do a demonstration system. The demonstration system was called a gopher after the U of Minnesota mascot--the golden gopher. The gopher proved to be very prolific, and within a few years there were over 10,000 gophers around the world. It takes no knowledge of unix or computer architecture to use. In a gopher system, you type or click on a number to select the menu selection you want.
Gopher's usability was enhanced much more when the University of Nevada at Reno developed the VERONICA searchable index of gopher menus. It was purported to be an acronym for Very Easy Rodent-Oriented Netwide Index to Computerized Archives. A spider crawled gopher menus around the world, collecting links and retrieving them for the index. It was so popular that it was very hard to connect to, even though a number of other VERONICA sites were developed to ease the load. Similar indexing software was developed for single sites, called JUGHEAD (Jonzy's Universal Gopher Hierarchy Excavation And Display).
In 1989 another significant event took place in making the nets easier to use. Tim Berners-Lee and others at the European Laboratory for Particle Physics, more popularly known as CERN, proposed a new protocol for information distribution. This protocol, which became the World Wide Web in 1991, was based on hypertext--a system of embedding links in text to link to other text, which you have been using every time you selected a text link while reading these pages. Although started before gopher, it was slower to develop.
Marc AndreessenThe development in 1993 of the graphical browser Mosaic by Marc Andreessen and his team at the National Center For Supercomputing Applications (NCSA) gave the protocol its big boost. Later, Andreessen moved to become the brains behind Netscape Corp., which produced the most successful graphical type of browser and server until Microsoft declared war and developed its MicroSoft Internet Explorer.
Since the Internet was initially funded by the government, it was originally limited to research, education, and government uses. Commercial uses were prohibited unless they directly served the goals of research and education. This policy continued until the early 90's, when independent commercial networks began to grow. It then became possible to route traffic across the country from one commercial site to another without passing through the government funded NSFNet Internet backbone.
Delphi was the first national commercial online service to offer Internet access to its subscribers. It opened up an email connection in July 1992 and full Internet service in November 1992. All pretenses of limitations on commercial use disappeared in May 1995 when the National Science Foundation ended its sponsorship of the Internet backbone, and all traffic relied on commercial networks. AOL, Prodigy, and CompuServe came online. Since commercial usage was so widespread by this time and educational institutions had been paying their own way for some time, the loss of NSF funding had no appreciable effect on costs.
Today, NSF funding has moved beyond supporting the backbone and higher educational institutions to building the K-12 and local public library accesses on the one hand, and the research on the massive high volume connections on the other.
During this period of enormous growth, businesses entering the Internet arena scrambled to find economic models that work. Free services supported by advertising shifted some of the direct costs away from the consumer--temporarily. Services such as Delphi offered free web pages, chat rooms, and message boards for community building. Online sales have grown rapidly for such products as books and music CDs and computers, but the profit margins are slim when price comparisons are so easy, and public trust in online security is still shaky. Business models that have worked well are portal sites, that try to provide everything for everybody, and live auctions. AOL's acquisition of Time-Warner was the largest merger in history when it took place and shows the enormous growth of Internet business! The stock market has had a rocky ride, swooping up and down as the new technology companies, the dot.com's encountered good news and bad. The decline in advertising income spelled doom for many dot.coms, and a major shakeout and search for better business models took place by the survivors.
A current trend with major implications for the future is the growth of high speed connections. 56K modems and the providers who supported them spread widely for a while, but this is the low end now. 56K is not fast enough to carry multimedia, such as sound and video except in low quality. But new technologies many times faster, such as cablemodems and digital subscriber lines (DSL) are predominant now.
Wireless has grown rapidly in the past few years, and travellers search for the wi-fi "hot spots" where they can connect while they are away from the home or office. Many airports, coffee bars, hotels and motels now routinely provide these services, some for a fee and some for free. A next big growth area is the surge towards universal wireless access, where almost everywhere is a "hot spot". Municipal wi-fi or city-wide access, wiMAX offering broader ranges than wi-fi, EV-DO, 4g, LTE, and other formats will joust for dominance in the USA in the years ahead. The battle is both economic and political.
Another trend that is rapidly affecting web designers is the growth of smaller devices to connect to the Internet. Small tablets, pocket PCs, smart phones, ebooks, game machines, and even GPS devices are now capable of tapping into the web on the go, and many web pages are not designed to work on that scale. As the Internet has become ubiquitous, faster, and increasingly accessible to non-technical communities, social networking and collaborative services have grown rapidly, enabling people to communicate and share interests in many more ways. Sites like Facebook, Twitter, Linked-In, YouTube, Flickr, Second Life, delicious, blogs, wikis, and many more let people of all ages rapidly share their interests of the moment with others everywhere.
1.3 HOW INTERNET WORKS?
The Internet is a network of networks—millions of them, actually. If the network at your university, your employer, or in your home has Internet access, it connects to an Internet service provider (ISP). Many (but not all) ISPs are big telecommunications companies like Verizon, Comcast, and AT&T2. These providers connect to one another, exchanging traffic, and ensuring your messages can get to any other computer that’s online and willing to communicate with you. The Internet has no center and no one owns it. That’s a good thing. The Internet was designed to be redundant and fault-tolerant—meaning that if one network, connecting wire, or server stops working, everything else should keep on running. Rising from military research and work at educational institutions dating as far back as the 1960s, the Internet really took off in the 1990s, when graphical Web browsing was invented, and much of the Internet’s operating infrastructure was transitioned to be supported by private firms rather than government grants.
Enough history—let’s see how it all works! If you want to communicate with another computer on the Internet then your computer needs to know the answer to three questions: What are you looking for? Where is it? And how do we get there? The computers and software that make up Internet infrastructure can help provide the answers. Let’s look at how it all comes together.
When you type an address into a Web browser (sometimes called a URL for uniform resource locator), you’re telling your browser what you’re looking for, Figure 2 describes how to read a typical URL.
The http:// you see at the start of most Web addresses stands for hypertext transfer protocol. A protocol is a set of rules for communication—sort of like grammar and vocabulary in a language like English. The http protocol defines how Web browser and Web servers communicate and is designed to be independent from the computer’s hardware and operating system. It doesn’t matter if messages come from a PC, a Mac, a huge mainframe, or a pocket-sized smartphone; if a device speaks to another using a common protocol, then it will be heard and understood.
The Internet supports lots of different applications, and many of these applications use their own application transfer protocol to communicate with each other. The server that holds your e-mail uses something called SMTP, or simple mail transfer protocol, to exchange mail with other email servers throughout the world. FTP, or file transfer protocol, is used for—you guessed it— file transfer. FTP is how most Web developers upload the Web pages, graphics, and other files for their Web sites. Even the Web uses different protocols. When you surf to an online bank or when you’re ready to enter your payment information at the Web site of an Internet retailer, the http at the beginning of your URL will probably change to https (the “s” is for secure). That means that communications between your browser and server will be encrypted for safe transmission. The beauty of the Internet infrastructure is that any savvy entrepreneur can create a new application that rides on top of the Internet.
1.3.1 Hosts and Domain Names
The next part of the URL in our diagram holds the host and domain name. Think of the domain
name as the name of the network you’re trying to connect to, and think of the host as the
computer you’re looking for on that network.
Many domains have lots of different hosts. For example, Yahoo!’s main Web site is served from
the host named “www” (at the address http://www.yahoo.com), but Yahoo! also runs other hosts
including those named “finance” (finance.yahoo.com), “sports” (sports.yahoo.com), and
“games” (games.yahoo.com).
Most Web sites are configured to load a default host, so you can often eliminate the host name if
you want to go to the most popular host on a site (the default host is almost always named
“www”). Another tip: most browsers will automatically add the “http://” for you, too.
Host and domain names are not case sensitive, so you can use a combination of upper and lower
case letters and you’ll still get to your destination.
1.3.2 Path Name and File Name
Look to the right of the top-level domain and you might see a slash followed by either a path
name, a file name, or both. If a Web address has a path and file name, the path maps to a folder
location where the file is stored on the server; the file is the name of the file you’re looking for.
Most Web pages end in “.html,” indicating they are in hypertext markup language. While http
helps browsers and servers communicate, html is the language used to create and format (render)
Web pages. A file, however, doesn’t need to be .html; Web servers can deliver just about any
type of file: Acrobat documents (.pdf), PowerPoint documents (.ppt or .pptx), Word docs (.doc or
.docx), JPEG graphic images (.jpg), and—as we’ll see in Chapter 13 "Information Security:
Barbarians at the Gateway (and Just About Everywhere Else)"—even malware programs that
attack your PC. At some Web addresses, the file displays content for every visitor, and at others
(like amazon.com), a file will contain programs that run on the Web server to generate custom
content just for you.
You don’t always type a path or file name as part of a Web address, but there’s always a file
lurking behind the scenes. A Web address without a file name will load content from a default
page. For example, when you visit “google.com,” Google automatically pulls up a page called
“index.html,” a file that contains the Web page that displays the Google logo, the text entry field,
the “Google Search” button, and so on. You might not see it, but it’s there.
1.4 ADDRESSING SCHEME IN THE INTERNET
An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g.,
computer, printer) participating in a computer network that uses the Internet Protocol for
communication3. An IP address serves two principal functions: host or network interface
identification and location addressing. Its role has been characterized as follows: "A name
indicates what we seek. An address indicates where it is. A route indicates how to get there.”
1.4.1 IP versions
Two versions of the Internet Protocol (IP) are in use: IP Version 4 and IP Version 6. Each
version defines an IP address differently. Because of its prevalence, the generic term IP address
typically still refers to the addresses defined by IPv4. The gap in version sequence between IPv4 and IPv6 resulted from the assignment of number 5 to the experimental Internet Stream Protocol
in 1979, which however was never referred to as IPv5.
1.4.2 IPv4 Addresses
In IPv4 an address consists of 32 bits which limits the address space to 4294967296 (232)
possible unique addresses. IPv4 reserves some addresses for special purposes such as private
networks (~18 million addresses) or multicast addresses (~270 million addresses). IPv4
addresses are canonically represented in dot-decimal notation, which consists of four decimal
numbers, each ranging from 0 to 255, separated by dots, e.g., 172.16.254.1. Each part represents
a group of 8 bits (octet) of the address. In some cases of technical writing, IPv4 addresses may be
presented in various hexadecimal, octal, or binary representations.
1.4.2.1 Subnetting
In the early stages of development of the Internet Protocol, network administrators interpreted an
IP address in two parts: network number portion and host number portion. The highest order
octet (most significant eight bits) in an address was designated as the network number and the
remaining bits were called the rest field or host identifier and were used for host numbering
within a network.
This early method soon proved inadequate as additional networks developed that were
independent of the existing networks already designated by a network number. In 1981, the
Internet addressing specification was revised with the introduction of classful network
architecture.
Classful network design allowed for a larger number of individual network assignments and finegrained
subnetwork design. The first three bits of the most significant octet of an IP address were
defined as the class of the address. Three classes (A, B, and C) were defined for universal unicast
addressing. Depending on the class derived, the network identification was based on octet
boundary segments of the entire address. Each class used successively additional octets in the
network identifier, thus reducing the possible number of hosts in the higher order classes (B and
C). The following table gives an overview of this now obsolete system.
Classful network design served its purpose in the startup stage of the Internet, but it lacked
scalability in the face of the rapid expansion of the network in the 1990s. The class system of the
address space was replaced with Classless Inter-Domain Routing (CIDR) in 1993. CIDR is based
on variable-length subnet masking (VLSM) to allow allocation and routing based on arbitrarylength
prefixes. Today, remnants of classful network concepts function only in a limited scope as
the default configuration parameters of some network software and hardware components (e.g.
netmask), and in the technical jargon used in network administrators' discussions.
1.4.2.2 Private Addresses
Early network design, when global end-to-end connectivity was envisioned for communications
with all Internet hosts, intended that IP addresses be uniquely assigned to a particular computer
or device. However, it was found that this was not always necessary as private networks
developed and public address space needed to be conserved.
Computers not connected to the Internet, such as factory machines that communicate only with
each other via TCP/IP, need not have globally unique IP addresses. Three non-overlapping
ranges of IPv4 addresses for private networks were reserved in RFC 1918. These addresses are
not routed on the Internet and thus their use need not be coordinated with an IP address registry.
Today, when needed, such private networks typically connect to the Internet through network
address translation (NAT). The designers of the Internet Protocol defined an IP address as a 32-
bit number and this system, known as Internet Protocol Version 4 (IPv4), is still in use today.
However, because of the growth of the Internet and the predicted depletion of available
addresses, a new version of IP (IPv6), using 128 bits for the address, was developed in 1995.
IPv6 was standardized as RFC 2460 in 1998, and its deployment has been ongoing since the
mid-2000s. IP addresses are usually written and displayed in human-readable notations, such as
172.16.254.1 (IPv4), and 2001:db8:0:1234:0:567:8:1 (IPv6). The Internet Assigned Numbers
Authority (IANA) manages the IP address space allocations globally and delegates five regional
Internet registries (RIRs) to allocate IP address blocks to local Internet registries (Internet service
providers) and other entities.
Any user may use any of the reserved blocks. Typically, a network administrator will divide a
block into subnets; for example, many home routers automatically use a default address range of
192.168.0.0 through 192.168.0.255 (192.168.0.0/24).
1.4.2.3 IPv4 address exhaustion
High levels of demand have decreased the supply of unallocated Internet Protocol Version 4
(IPv4) addresses available for assignment to Internet service providers and end user
organizations since the 1980s. This development is referred to as IPv4 address exhaustion.
IANA's primary address pool was exhausted on 3 February 2011, when the last five blocks were
allocated to the five RIRs. APNIC was the first RIR to exhaust its regional pool on 15 April
2011, except for a small amount of address space reserved for the transition to IPv6, intended to
be allocated in a restricted process.
1.4.3 IPv6 Addresses
The rapid exhaustion of IPv4 address space prompted the Internet Engineering Task Force
(IETF) to explore new technologies to expand the addressing capability in the Internet. The
permanent solution was deemed to be a redesign of the Internet Protocol itself. This new
generation of the Internet Protocol was eventually named Internet Protocol Version 6 (IPv6) in
1995. The address size was increased from 32 to 128 bits (16 octets), thus providing up to 2128
(approximately 3.403×1038) addresses. This is deemed sufficient for the foreseeable future.
The intent of the new design was not to provide just a sufficient quantity of addresses, but also
redesign routing in the Internet by more efficient aggregation of subnetwork routing prefixes.
This resulted in slower growth of routing tables in routers. The smallest possible individual
allocation is a subnet for 264 hosts, which is the square of the size of the entire IPv4 Internet. At
these levels, actual address utilization rates will be small on any IPv6 network segment. The new
design also provides the opportunity to separate the addressing infrastructure of a network
segment, i.e. the local administration of the segment's available space, from the addressing prefix
used to route traffic to and from external networks. IPv6 has facilities that automatically change
the routing prefix of entire networks, should the global connectivity or the routing policy change,
without requiring internal redesign or manual renumbering. The large number of IPv6 addresses
allows large blocks to be assigned for specific purposes and, where appropriate, to be aggregated
for efficient routing. With a large address space, there is no need to have complex address
conservation methods as used in CIDR.
All modern desktop and enterprise server operating systems include native support for the IPv6
protocol, but it is not yet widely deployed in other devices, such as residential networking
routers, voice over IP (VoIP) and multimedia equipment, and network peripherals.
1.4.3.1 Private addresses
Just as IPv4 reserves addresses for private networks, blocks of addresses are set aside in IPv6. In
IPv6, these are referred to as unique local addresses (ULA). RFC 4193 reserves the routing
prefix fc00::/7 for this block which is divided into two /8 blocks with different implied policies.
The addresses include a 40-bit pseudorandom number that minimizes the risk of address
collisions if sites merge or packets are misrouted.
Early practices used a different block for this purpose (fec0::), dubbed site-local addresses.
However, the definition of what constituted sites remained unclear and the poorly defined
addressing policy created ambiguities for routing. This address type was abandoned and must not
be used in new systems.
Addresses starting with fe80:, called link-local addresses, are assigned to interfaces for
communication on the attached link. The addresses are automatically generated by the operating
system for each network interface. This provides instant and automatic communication between
all IPv6 host on a link. This feature is required in the lower layers of IPv6 network
administration, such as for the Neighbor Discovery Protocol. Private address prefixes may not be
routed on the public Internet.
1.4.4 IP Subnetworks
IP networks may be divided into subnetworks in both IPv4 and IPv6. For this purpose, an IP
address is logically recognized as consisting of two parts: the network prefix and the host
identifier, or interface identifier (IPv6). The subnet mask or the CIDR prefix determines how the
IP address is divided into network and host parts.
The term subnet mask is only used within IPv4. Both IP versions however use the CIDR concept
and notation. In this, the IP address is followed by a slash and the number (in decimal) of bits
used for the network part, also called the routing prefix. For example, an IPv4 address and its
subnet mask may be 192.0.2.1 and 255.255.255.0, respectively. The CIDR notation for the same
IP address and subnet is 192.0.2.1/24, because the first 24 bits of the IP address indicate the
network and subnet.
1.4.5 IP address assignment
Internet Protocol addresses are assigned to a host either anew at the time of booting, or
permanently by fixed configuration of its hardware or software. Persistent configuration is also
known as using a static IP address. In contrast, in situations when the computer's IP address is
assigned newly each time, this is known as using a dynamic IP address.
1.4.5.1 Methods
Static IP addresses are manually assigned to a computer by an administrator. The exact
procedure varies according to platform. This contrasts with dynamic IP addresses, which are
assigned either by the computer interface or host software itself, as in Zeroconf, or assigned by a
server using Dynamic Host Configuration Protocol (DHCP). Even though IP addresses assigned
using DHCP may stay the same for long periods of time, they can generally change. In some
cases, a network administrator may implement dynamically assigned static IP addresses. In this
case, a DHCP server is used, but it is specifically configured to always assign the same IP
address to a particular computer. This allows static IP addresses to be configured centrally,
without having to specifically configure each computer on the network in a manual procedure.
In the absence or failure of static or stateful (DHCP) address configurations, an operating system
may assign an IP address to a network interface using state-less auto-configuration methods,
such as Zeroconf.
1.4.5.2 Uses of dynamic address assignment
IP addresses are most frequently assigned dynamically on LANs and broadband networks by the
Dynamic Host Configuration Protocol (DHCP). They are used because it avoids the
administrative burden of assigning specific static addresses to each device on a network. It also
allows many devices to share limited address space on a network if only some of them will be
online at a particular time. In most current desktop operating systems, dynamic IP configuration
is enabled by default so that a user does not need to manually enter any settings to connect to a
network with a DHCP server. DHCP is not the only technology used to assign IP addresses
dynamically. Dialup and some broadband networks use dynamic address features of the Point-to-
Point Protocol.
1.4.5.2.1 Sticky dynamic IP address
A sticky dynamic IP address is an informal term used by cable and DSL Internet access
subscribers to describe a dynamically assigned IP address which seldom changes. The addresses
are usually assigned with DHCP. Since the modems are usually powered on for extended periods of time, the address leases are usually set to long periods and simply renewed. If a modem is
turned off and powered up again before the next expiration of the address lease, it will most
likely receive the same IP address.
1.4.5.3 Address autoconfiguration
RFC 3330 defines an address block, 169.254.0.0/16, for the special use in link-local addressing
for IPv4 networks. In IPv6, every interface, whether using static or dynamic address
assignments, also receives a local-link address automatically in the block fe80::/10.
These addresses are only valid on the link, such as a local network segment or point-to-point
connection, that a host is connected to. These addresses are not routable and like private
addresses cannot be the source or destination of packets traversing the Internet.
When the link-local IPv4 address block was reserved, no standards existed for mechanisms of
address autoconfiguration. Filling the void, Microsoft created an implementation that is called
Automatic Private IP Addressing (APIPA). APIPA has been deployed on millions of machines
and has, thus, become a de facto standard in the industry. In RFC 3927, the IETF defined a
formal standard for this functionality, entitled Dynamic Configuration of IPv4 Link-Local
Addresses.
1.4.5.4 Uses of static addressing
Some infrastructure situations have to use static addressing, such as when finding the Domain
Name System (DNS) host that will translate domain names to IP addresses. Static addresses are
also convenient, but not absolutely necessary, to locate servers inside an enterprise. An address
obtained from a DNS server comes with a time to live, or caching time, after which it should be
looked up to confirm that it has not changed. Even static IP addresses do change as a result of
network administration (RFC 2072).
1.4.5.5 Conflict
An IP address conflict occurs when two devices on the same local physical or wireless network
claim to have the same IP address - that is, they conflict with each other. Since only one of the
devices is supposed to be on the network at a time, the second one to arrive will generally stop
the IP functionality of one or both of the devices. In many cases with modern Operating Systems,
the Operating System will notify the user of one of the devices that there is an IP address conflict
(displaying the symptom error message) and then either stop functioning on the network or
function very badly on the network, and the user will then be stumped as to how to resolve the
conflict, probably considering the situation an emergency. In some unfortunate cases, both
devices will function very badly on the network. In severe cases in which one of the devices is
the gateway, the network will be crippled. Since IP addresses are assigned by multiple people
and systems in multiple ways, any of them can be at fault.
1.4.6 Routing
IP addresses are classified into several classes of operational characteristics: unicast, multicast,
anycast and broadcast addressing.
1.4.6.1 Unicast addressing
The most common concept of an IP address is in unicast addressing, available in both IPv4 and
IPv6. It normally refers to a single sender or a single receiver, and can be used for both sending
and receiving. Usually, a unicast address is associated with a single device or host, but a device
or host may have more than one unicast address. Some individual PCs have several distinct
unicast addresses, each for its own distinct purpose. Sending the same data to multiple unicast
addresses requires the sender to send all the data many times over, once for each recipient.
1.4.6.2 Broadcast addressing
In IPv4 it is possible to send data to all possible destinations ("all-hosts broadcast"), which
permits the sender to send the data only once, and all receivers receive a copy of it. In the IPv4
protocol, the address 255.255.255.255 is used for local broadcast. In addition, a directed
(limited) broadcast can be made by combining the network prefix with a host suffix composed
entirely of binary 1s. For example, the destination address used for a directed broadcast to
devices on the 192.0.2.0/24 network is 192.0.2.255. IPv6 does not implement broadcast
addressing and replaces it with multicast to the specially-defined all-nodes multicast address.
1.4.6.3 Multicast addressing
A multicast address is associated with a group of interested receivers. In IPv4, addresses
224.0.0.0 through 239.255.255.255 (the former Class D addresses) are designated as multicast
addresses. IPv6 uses the address block with the prefix ff00::/8 for multicast applications. In
either case, the sender sends a single datagram from its unicast address to the multicast group
address and the intermediary routers take care of making copies and sending them to all receivers
that have joined the corresponding multicast group.
1.4.6.4 Anycast addressing
Like broadcast and multicast, anycast is a one-to-many routing topology. However, the data
stream is not transmitted to all receivers, just the one which the router decides is logically closest
in the network. Anycast address is an inherent feature of only IPv6. In IPv4, anycast addressing
implementations typically operate using the shortest-path metric of BGP routing and do not take
into account congestion or other attributes of the path. Anycast methods are useful for global
load balancing and are commonly used in distributed DNS systems.
1.4.7 Public addresses
A public IP address, in common parlance, is synonymous with a globally routable unicast IP
address. Both IPv4 and IPv6 define address ranges that are reserved for private networks and
link-local addressing. The term public IP address often used excludes these types of addresses.
1.4.8 Modifications to IP addressing
1.4.8.1 IP blocking and firewalls
Firewalls perform Internet Protocol blocking to protect networks from unauthorized access. They
are common on today's Internet. They control access to networks based on the IP address of a
client computer. Whether using a blacklist or a whitelist, the IP address that is blocked is the perceived IP address of the client, meaning that if the client is using a proxy server or network
address translation, blocking one IP address may block many individual computers.
1.4.8.2 IP address translation
Multiple client devices can appear to share IP addresses: either because they are part of a shared
hosting web server environment or because an IPv4 network address translator (NAT) or proxy
server acts as an intermediary agent on behalf of its customers, in which case the real originating
IP addresses might be hidden from the server receiving a request. A common practice is to have
a NAT hide a large number of IP addresses in a private network. Only the "outside" interface(s)
of the NAT need to have Internet-routable addresses.
Most commonly, the NAT device maps TCP or UDP port numbers on the side of the larger,
public network to individual private addresses on the masqueraded network. In small home
networks, NAT functions are usually implemented in a residential gateway device, typically one
marketed as a "router". In this scenario, the computers connected to the router would have
private IP addresses and the router would have a public address to communicate on the Internet.
This type of router allows several computers to share one public IP address.
1.5 INTERNET SERVICE PROVIDER
An Internet service provider (ISP) is an organization that provides services for accessing, using,
or participating in the Internet5. Internet service providers may be organized in various forms,
such as commercial, community-owned, non-profit, or otherwise privately owned. Internet
services typically provided by ISPs include Internet access, Internet transit, domain name
registration, web hosting, Usenet service, and collocation.
1.5.1 Classification of ISP6
1.5.1.1 Access providers ISP
ISPs provide Internet access, employing a range of technologies to connect users to their
network. Available technologies have ranged from computer modems with acoustic couplers to
telephone lines, to television cable (CATV), wireless Ethernet (wi-fi), and fiber optics.
For users and small businesses, traditional options include copper wires to provide dial-up, DSL
(typically asymmetric digital subscriber line (ADSL), cable modem or Integrated Services
Digital Network (ISDN) (typically basic rate interface). Using fiber-optics to end users is called
Fiber To The Home or similar names. For customers with more demanding requirements (such
as medium-to-large businesses, or other ISPs) can use higher-speed DSL (such as single-pair
high-speed digital subscriber line), Ethernet, metropolitan Ethernet, gigabit Ethernet, Frame
Relay, ISDN Primary Rate Interface, ATM (Asynchronous Transfer Mode) and synchronous
optical networking (SONET). Wireless access is another option, including satellite Internet
access.
1.5.1.2 Mailbox providers
A mailbox provider is an organization that provides services for hosting electronic mail domains
with access to storage for mail boxes. It provides email servers to send, receive, accept, and store
email for end users or other organizations. Many mailbox providers are also access providers,
while others are not (e.g., Yahoo! Mail, Outlook.com, Gmail, AOL Mail, Po box). The definition
given in RFC 6650 covers email hosting services, as well as the relevant department of
companies, universities, organizations, groups, and individuals that manage their mail servers
themselves. The task is typically accomplished by implementing Simple Mail Transfer Protocol
(SMTP) and possibly providing access to messages through Internet Message Access Protocol
(IMAP), the Post Office Protocol, Webmail, or a proprietary protocol.
1.5.1.3 Hosting ISPs
Internet hosting services provide email, web-hosting, or online storage services. Other services
include virtual server, cloud services, or physical server operation.
1.5.1.4 Transit ISP
Just as their customers pay them for Internet access, ISPs themselves pay upstream ISPs for
Internet access. An upstream ISP usually has a larger network than the contracting ISP or is able
to provide the contracting ISP with access to parts of the Internet the contracting ISP by itself has
no access to. In the simplest case, a single connection is established to an upstream ISP and is
used to transmit data to or from areas of the Internet beyond the home network; this mode of
interconnection is often cascaded multiple times until reaching a tier 1 carrier. In reality, the
situation is often more complex. ISPs with more than one point of presence (PoP) may have
separate connections to an upstream ISP at multiple PoPs, or they may be customers of multiple
upstream ISPs and may have connections to each one of them at one or more point of presence.
Transit ISPs provide large amounts of bandwidth for connecting hosting ISPs and access ISPs.
1.5.1.5 Virtual ISPs
A virtual ISP (VISP) is an operation that purchases services from another ISP, sometimes called
a wholesale ISP in this context, which allow the VISP's customers to access the Internet using
services and infrastructure owned and operated by the wholesale ISP. VISPs resemble mobile
virtual network operators and competitive local exchange carriers for voice communications.
1.5.1.6 Free ISPs
Free ISPs are Internet service providers that provide service free of charge. Many free ISPs
display advertisements while the user is connected; like commercial television, in a sense they
are selling the user's attention to the advertiser. Other free ISPs, sometimes called freenets, are
run on a nonprofit basis, usually with volunteer staff.
1.5.1.7 Wireless ISP
A wireless internet service provider (WISP) is an Internet service provider with a network based
on wireless networking. Technology may include commonplace Wi-Fi wireless mesh
networking, or proprietary equipment designed to operate over open 900 MHz, 2.4 GHz, 4.9, 5.2,
5.4, 5.7, and 5.8 GHz bands or licensed frequencies such as 2.5 GHz (EBS/BRS), 3.65 GHz
(NN) and in the UHF band (including the MMDS frequency band) and LMDS.
1.6 DOMAIN NAME SYSTEM(DNS)
The Domain Name System (DNS) is the system used to translate alphanumeric domain names
into Internet Protocol numbers. Simply put, the DNS converts the names typed in the Web
browser address bar into IP addresses7. The DNS is made up of many servers and databases
which, through a series of lookups in various caches, configure Domain Names into IP
Addresses. The Domain Name System is a distributed database arranged hierarchically; its
purpose is to provide a layer of abstraction between Internet services (web, email, etc.) and the
numeric addresses (IP addresses) used to uniquely identify any given machine on the Internet.
The DNS associates a variety of information with the domain names assigned and, most
importantly, translates the domain names meaningful to humans into the numerical identifiers
that locate the desired destination.
1.6.1 How does it work?
The DNS makes it possible to assign domain names in a meaningful way to Internet resources as
well as to users, regardless of the entity's location. As a result, the WWW hyperlinks remain
consistent, even for mobile devices. A domain name is an easy way to remember an address, but
that needs to be converted to its numerical, IP format.
Coordination across the Internet is maintained by means of a complex authoritative root system
known as the Top Level Domain (TLD), as well as the DNS and other smaller name servers
responsible for hosting individual domain information.
DNS includes three types of top-level domains: generic (gTLD), country code (ccTLD), and
sponsored (sTLD). gTLDs include domains that could be obtained by anyone (.com, .info, .net,
and .org). Since 2014 many other gTLDs have been added like .pub, .ngo, .sucks. sTLDs are
limited to a specific group e.g .aero (for air-transport industry).
For each domain, the DNS spreads the responsibility by mapping the domain names and
assigning them into IP addresses, and vice-versa. This is accomplished through authoritative
name servers which have been designated for each domain. Each authoritative name server is
responsible for its own particular domain, but it has the authority to assign new authoritative
name servers to any of its sub-domains. The DNS is able to store many types of information,
even the mail server lists for a specific domain. The DNS is a core element which ensures the
functionality of the Internet through its distributed keyword-based redirection service.
However, the DNS does not include security extensions, which was instead developed as
DNSSEC.
1.6.1.1Top-Level Domain(TLD)8
Whenever you use a domain name, in a web address (URL), email address, or wherever, it
ends in a "top-level domain" or "TLD". This is the last part of the name. We often thing of .COM,
.ORG, .NET, etc., as in:
• www.disruptiveconversations.COM
• www.forimmediaterelease.BIZ
• internetsociety.ORG
TLDs are broadly classified into two categories:
a. generic top-level domains (gTLDs)
b. country code top-level domains (ccTLDs)
The entity responsible for the administration of these TLDs in the "root" of the Domain Name
System (DNS) is the Internet Assigned Numbers Authority (IANA) that is currently operated by
the Internet Corporation for Assigned Names and Numbers (ICANN). You can see the full list of current
TLDs at: https://www.iana.org/domains/root/db
1.6.1.2 Second-Level Domain
The next part of the domain name to the left of the TLD (and separated by a dot) is the "secondlevel
domain". These are the domains that you are typically able to register with a registrar.
Examples include:
• www.disruptiveconversations.com
• www.forimmediaterelease.biz
• internetsociety.org
The next part of the domain name to the left ("www" in the first two examples above) would be
called the "third-level domain", and so on.
a. gTLD (Generic Top-Level Domain): Generic top-level domains (gTLDs) are TLDs that are
not tied to any specific country and are "generic" in terms of being able to be used (in
theory, anyway) by anyone on the Internet anywhere in the world. The "original" TLDs
such as .COM, .ORG, .NET, .GOV, .MIL are all classified as "generic TLDs". There
were a couple of rounds of "expansion" of the gTLDs that brought the total to 22 gTLDs
prior to the "newgTLD" expansion currently underway
b. ccTLD (Country Code Top-Level Domain): Country code top-level domains(ccTLDs)
are two letter TLDs that are assigned to countries based mostly on the ISOC 3166 list of country
codes. Some countries have chosen to operate their ccTLD exclusively for domains within
their country or geographic territory. Some do not allow people to register "second-level
domains" under the TLD and instead require people to register third-level domains under
one of several different second-level domains. For example, the .UK domain as to date
required registrations to be under domains such as ".co.uk" and ".org.uk", basically
duplicating part of the original gTLD scheme inside their ccTLD.
Many ccTLDs have chosen NOT to restrict their ccTLD to people in their country and
have in fact marketed their domains very widely encouraging everyone to use them.
Some prominent examples of this include Columbia(.CO), Montenegro(.ME),
Tuvulu(.TV), Federated States of Micronesia(.FM) and many more. Essentially, any time
you are using a two-letter TLD, it is a ccTLD for some country.
c. newgTLD Top-Level Domain: After many years of discussion, ICANN's board voted in
2011 to allow the creation of new generic TLDs using almost any text string (and in
multiple character sets) and began the "newgTLD" program. This resulted in 1,930
applications by various companies to operate new gTLDs. These newgTLDs are now being
rolled out in phases and people are able to register second-level domains under many of
these domains. More newgTLDs are being made available pretty much every week - and
the expansion will continue for many months and years ahead of us.
At a technical level, "new gTLDs" are effectively the same as "gTLDs"... the designation
is just really that these new gTLDs are coming out in this current round of expansion.
d. IDN = Internationalized Domain Name: The original TLDs were all in the ASCII character
set, but over time ICANN decided to allow the creation of "internationalized domain
names"(IDNs) that use other character sets such as Cyrillic, Arabic, Chinese, Korean, etc.
The first IDN for a country code TLD appeared in 2010 and the newgTLDs contain many
IDNs. (In fact, the very first of the "newgTLDs" were four IDNs.)
1.7 WORLD WIDE WEB(WWW)
The World Wide Web, is a system of interlinked hypertext documents accessed via the Internet.
With a web browser, one can view web pages that may contain text, images, videos, and other
multimedia, and navigate between them via hyperlinks. Using concepts from his earlier hypertext
systems like ENQUIRE, British engineer, computer scientist and at that time employee of CERN, Sir Tim Berners-Lee, now Director of the World Wide Web Consortium, wrote a
proposal in March 1989 for what would eventually become the World Wide Web9.
1.7.1 Is Intenet and www similler?
The world wide web is just one way to access information through the internet10. While it does
represent a considerable portion of the internet, and is unquestionably the most popular part, the
two concepts must not be treated as synonyms because they are not the same. We tend to become
used to calling things by the simplest possible name but we also tend to muddle concepts and
mix up one thing with another when the distinction between them isn’t very clear. One very
common case of this is the fact that most people tend to refer to “the web” and “internet” as if
they were exactly the same thing, when in fact they’re not. It can be rather confusing, and even a
surprise for many, but the internet and the web are two different things, and one is above the
other. Let’s see what this means.
1.7.1.1 The www
The three Ws that are in the addresses of the websites we access. The world wide web or simply
the “web”, is a way to access information through the internet. The web is a model for sharing
information that is built on the internet. The protocol used by the web is HTTP, just one of the
many ways that information can be sent through the internet.
If a service uses HTTP to enable applications to communicate with each other, this is a web
service. Web browsers, such as Chrome or Firefox, enable us to access web documents that we
mainly know as web pages or websites. These sites are connected to each other through
hyperlinks as if they were on a spider’s web (hence the name), and all this thanks to the transfer
protocol: HTTP.
Therefore, the web is only one of the ways that information can flow through the internet: it is
just a portion, and although it is very large and the most popular part, it does not include the
whole of the internet.
1.7.1.2 The Internet
The internet is a massive network, the network of networks. The internet connects millions of
computers across the globe through a network that enables any computer to be able to
communicate with another, no matter where on the planet they are, provided they are both
connected to the internet. A network is any connection between two or more clients. For
example, you can access a local network in your home that only the computers of the members
of your family can access and which are connected through a switcher or router, or a work
network that only people working at the same firm can access. The internet is a global, largescale
network that enables millions and millions of devices to connect at the same time, and is
completely free and open.
All the information that travels through the internet does so through a protocol; there are several
of these. As we have already explained, the HTTP protocol is the one used by the web to share information. Therefore, web pages such as Twitter, Google, Facebook and even this blog are part
of the web and this information travels to us all through the internet.
When it comes down to it, the world won’t end if we continue using the terms interchangeably –
after all, habits are hard to break – but it is a good thing to be clear about the concepts, at least.
1.8 APPLICATION OF INTERNET
Internet have become an essential component of our daily lives. But what does one do with the
Internet? May be four things, basically: mail, discussion groups, long-distance computing, and
file transfers. Internet mail is (e-mail or electronic mail), much faster as compared to normal
postal mail11. One can also send software and certain forms of compressed digital image as an
attachment. News groups or discussion groups facilitate Internet user to join for various kinds of
debate, discussion and news sharing. Long-distance computing was an original inspiration for
development of ARPANET and does still provide a very useful service on Internet. Programmers
can maintain accounts on distant, powerful computers, execute programs. File transfer service
allows Internet users to access remote machines and retrieve programs, data or text.
We can roughly separate internet applications into the following types: online media, online
information search, online communications, online communities, online entertainment, ebusiness,
online finance and other applications. The internet is treated as one of the biggest
invention. It has a large number of uses.
1. Communication
2. Job searches
3. Finding books and study material
4. Health and medicine
5. Travel
6. Entertainment
7. Shopping
8. Stock market updates
9. Research
10. Business use of internet: different ways by which intenet can be used for business are:
a. Information about the product can be provided can be provided online to the
the customer
b. Provide market information to the business
c. It help business to recruit talented people
d. Help in locating suppliers of the product
e. Fast information regarding customers view about companies product
f. Eliminate middle men and have a direct contact with contact with customer
g. Providing information to the investor by providing companies back ground and
financial information on web site.