Introduction to networks and Internet

UNIT – 2 The Internet

Introduction to networks and Internet


Network:
A network is a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain sub networks.
A group of two or more computer systems linked together. There are many types of computer networks, including:
· Local-area networks (LANs) : The computers are geographically close together (that is, in the same building).
· Wide-area networks (WANs) : The computers are farther apart and are connected by telephone lines or radio waves.
· Metropolitan-area networks MANs): A data network designed for a town or city.

In addition to these types, the following characteristics are also used to categorize different types of networks:
· Topology : The geometric arrangement of a computer system. Common topologies include a bus, star, and ring. See the Network topology diagrams.
· Protocol : The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called Ethernet. Another popular LAN protocol for PCs is the IBM token-ring network.
· Architecture : Networks can be broadly classified as using either a peer-to-peer or client/server architecture.
Computers on a network are sometimes called nodes. Computers and devices that allocate resources for a network are called servers.

Internet:
The Internet is a global system of interconnected computer networks that interchange data by packet switching using the standardized Internet Protocol Suite (TCP/IP). It is a "network of networks" that consists of millions of private and public, academic, business, and government networks of local to global scope that are linked by copper wires, fiber-optic cables, wireless connections, and other technologies.
The Internet carries various information resources and services, such as electronic mail, online chat, file transfer and file sharing, online gaming, and the inter-linked hypertext documents and other resources of the World Wide Web (WWW).


History of Internet
The history of the Internet began with the ARPANET and connected mainframe computers on dedicated connections. The second stage involved adding desktop PCs which connected through telephone wires. The third stage was adding wireless connections to laptop computers. And currently the Internet is evolving to allow mobile phone Internet connectivity ubiquitously using cellular networks.
The ARPANET (Advanced Research Projects Agency Network) developed by ARPA of the United States Department of Defense, was the world's first operational packet switching network, and the predecessor of the global Internet.
Packet switching, now the dominant basis for both data and voice communication worldwide, was a new and important concept in data communications. Previously, data communication was based on the idea of circuit switching, as in the old typical telephone circuit, where a dedicated circuit is tied up for the duration of the call and communication is only possible with the single party on the other end of the circuit.
Before the Internet:
In the 1950s and early 1960s, prior to the widespread inter-networking that led to the Internet, most communication networks were limited in that they only allowed communications between the stations on the network. Some networks had gateways or bridges between them, but these bridges were often limited or built specifically for a single use. One prevalent computer networking method was based on the central mainframe method, simply allowing its terminals to be connected via long leased lines.
Three terminals and an ARPA
A fundamental pioneer in the call for a global network, J.C.R. Licklider, articulated the ideas in his January 1960 paper, Man-Computer Symbiosis.
"A network of such [computers], connected to one another by wide-band communication lines [which provided] the functions of present-day libraries together with anticipated advances in information storage and retrieval and [other] symbiotic functions."
—J.C.R. Licklider, [2]
In October 1962, Licklider was appointed head of the United States Department of Defense's Advanced Research Projects Agency, now known as DARPA, within the information processing office. There he formed an informal group within DARPA to further computer research. As part of the information processing office's role, three network terminals had been installed: one for System Development Corporation in Santa Monica, one for Project Genie at the University of California, Berkeley and one for the Compatible Time-Sharing System project at the Massachusetts Institute of Technology (MIT). Licklider's identified need for inter-networking would be made obvious by the apparent waste of resources this caused.
"For each of these three terminals, I had three different sets of user commands. So if I was talking online with someone at S.D.C. and I wanted to talk to someone I knew at Berkeley or M.I.T. about this, I had to get up from the S.D.C. terminal, go over and log into the other terminal and get in touch with them. [...] I said, it's obvious what to do (But I don't want to do it): If you have these three terminals, there ought to be one terminal that goes anywhere you want to go where you have interactive computing. That idea is the ARPAnet."
Networks that led to the Internet
ARPANET
Promoted to the head of the information processing office at DARPA, Robert Taylor intended to realize Licklider's ideas of an interconnected networking system. Bringing in Larry Roberts from MIT, he initiated a project to build such a network. The first ARPANET link was established between the University of California, Los Angeles and the Stanford Research Institute on 22:30 hours on October 29, 1969. By 5 December 1969, a 4-node network was connected by adding the University of Utah and the University of California, Santa Barbara. Building on ideas developed in ALOHAnet, the ARPANET grew rapidly. By 1981, the number of hosts had grown to 213, with a new host being added approximately every twenty days.
ARPANET became the technical core of what would become the Internet, and a primary tool in developing the technologies used. ARPANET development was centered around the Request for Comments (RFC) process, still used today for proposing and distributing Internet Protocols and Systems. RFC 1, entitled "Host Software", was written by Steve Crocker from the University of California, Los Angeles, and published on April 7, 1969. These early years were documented in the 1972 film Computer Networks: The Heralds of Resource Sharing.
International collaborations on ARPANET were sparse. For various political reasons, European developers were concerned with developing the X.25 networks. Notable exceptions were the Norwegian Seismic Array (NORSAR) in 1972, followed in 1973 by Sweden with satellite links to the Tanum Earth Station and University College London.
X.25 and public access
Following on from ARPA's research, packet switching network standards were developed by the International Telecommunication Union (ITU) in the form of X.25 and related standards. In 1974, X.25 formed the basis for the SERCnet network between British academic and research sites, which later became JANET. The initial ITU Standard on X.25 was approved in March 1976. This standard was based on the concept of virtual circuits.
The British Post Office, Western Union International and Tymnet collaborated to create the first international packet switched network, referred to as the International Packet Switched Service (IPSS), in 1978. This network grew from Europe and the US to cover Canada, Hong Kong and Australia by 1981. By the 1990s it provided a worldwide networking infrastructure.
Unlike ARPAnet, X.25 was also commonly available for business use. Telenet offered its Telemail electronic mail service, but this was oriented to enterprise use rather than the general email of ARPANET.

Working of Internet

Internet is a Wide Area Network (WAN) spread allover the world which is used to connect different types of networks. This process of interconnecting the different kinds of networks is known as Internetworking.




The device used for Internetworking is router(R).



Because 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 nnn must be a number from 0 - 255. This address is known as an IP address. (IP stands for Internet Protocol)
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.


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.
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
Comments
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 "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. 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 it's 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, "Hello computer 5.6.7.8!"


Internet-culture
Internet-culture is the culture that has emerged, or is emerging, from the use of computer networks for communication, entertainment and business.
Internet-culture is a wide social and cultural movement closely linked to advanced information science and information technology, their emergence, development and rise to social and cultural prominence between the 1960s and the 1990s. Internet-culture was influenced at its genesis by those early users of the internet, frequently including the architects of the original project. These individuals were often guided in their actions by the hacker ethic. While early internet-culture was based on a small cultural sample, and its ideals, the modern internet-culture is a much more diverse group of users and the ideals that they adopt.
Demonstration of Internet-culture
Demonstration of Internet-culture includes various human interactions mediated by computer networks.
They can be activities, pursuits, games, places and metaphors, and include a diverse base of applications. Some are supported by specialized software and others work on commonly accepted web protocols. Examples include but are not limited to:
Blogs
Social Networks
Games
Chat
USENET
Bulletin Board Systems
E-Commerce
Peer to Peer Networks
Virtual worlds
Features of Internet-culture
There are several features that internet-cultures share that make them warrant the prefix “cyber-“. Some of those qualities are that internet-culture:
Is a community mediated by ICTs(Information and Communications Technology).
Is culture “mediated by computer screens.”
Relies heavily on the notion of information and knowledge exchange.
Depends on the ability to manipulate tools to a degree not present in other forms of culture (even artisan culture, e.g., a glass-blowing culture).
Allows vastly expanded weak ties and has been criticized for overly emphasizing the same (see Bowling Alone and other works).
Multiplies the number of eyeballs on a given problem, beyond that which would be possible using traditional means, given physical, geographic, and temporal constraints.
Is a “cognitive and social culture, not a geographic one.”
Is “the product of like-minded people finding a common ‘place’ to interact."[10]
Is inherently more "fragile" than traditional forms of community and culture.
Identity in Internet-culture
Internet-culture, like culture in general, relies on establishing identity and credibility. However, in the absence of direct physical interaction, it could be argued that the process for such establishment is more difficult.
How does internet-culture rely on and establish identity and credibility? This relationship is two way, with identity and credibility being both used to define community in cyberspace and to be created within and by online communities.
In some senses, online credibility is established in much the same way that it is established in the off line world, however, since there are two separate worlds, it is not surprising that there are both differences in the mechanisms found in each and interactions of the markers found in each.
Architectures of Credibility
Following the model put forth by Lawrence Lessig in Code 2.0[11], the architecture of a given online community may be the single most important factor regulating the establishment of credibility within online communities. Some factors may be:
· Anonymous versus Known
· Linked to Physical Identity versus Internet-based Identity Only
· Unrated Commentary System versus Rated Commentary System
· Positive Feedback-oriented versus Mixed Feedback (positive and negative) oriented
· Moderated versus Unmoderated
Anonymous versus KnownMany sites allow anonymous commentary, where the user-id attached to the comment is something like "guest" or "anonymous user". In an architecture that allows anonymous posting about other works, the credibility being impacted is only that of the product for sale, the original opinion expressed, the code written, the YouTube video, or other entity about which comments are made (e.g., a Slashdot post). Sites that require "known" postings can vary widely from simply requiring some kind of name to be associated with the comment to requiring registration, wherein the identity of the registrant is visible to other readers of the comment. These "known" identities allow and even require commentators to be aware of their own credibility, based on the fact that other users will associate particular content and styles with their identity. By definition, then, all blog postings are "known" in that the blog exists in a consistently defined virtual location, which helps to establish an identity, around which credibility can gather. Note that a "known" identity need have nothing to do with a given identity in the physical world.
Linked to Physical Identity versus Internet-based Identity OnlyArchitectures can require that physical identity be associated with commentary, as in Lessig's example of Counsel Connect.However, to require linkage to physical identity, many more steps must be taken (collecting and storing sensitive information about a user) and safeguards for that collected information must be established-the users must have more trust of the sites collecting the information (yet another form of credibility). Irrespective of safeguards, as with Counsel Connect[12], using physical identities links credibility across the frames of the internet and real space, influencing the behaviors of those who contribute in those spaces. However, even purely internet-based identities have credibility. Just as Lessig describes linkage to a character or a particular online gaming environment, nothing inherently links a person or group to their internet-based persona, but credibility (similar to "characters") is "earned rather than bought, and because this takes time and (credibility is) not fungible, it becomes increasingly hard" to create a new persona.
Unrated Commentary System versus Rated Commentary SystemIn some architectures those who review or offer comments can, in turn, be rated by other users. This technique offers the ability to regulate the credibility of given authors by subjecting their comments to direct "quantifiable" approval ratings.
Positive Feedback-oriented versus Mixed Feedback (positive and negative) orientedArchitectures can be oriented around positive feedback or a mix of both positive and negative feedback. While a particular user may be able to equate fewer stars with a "negative" rating, the semantic difference is potentially important. The ability to actively rate an entity negatively may violate laws or norms that are important in the jurisdiction in which the internet property is important. The more public a site, the more important this concern may be, as noted by Goldsmith & Wu regarding eBay.
Moderated versus UnmoderatedArchitectures can also be oriented to give editorial control to a group or individual. Many email lists are worked in this fashion (e.g., Freecycle). In these situations, the architecture usually allows, but does not require that contributions be moderated. Further, moderation may take two different forms: reactive or proactive. In the reactive mode, an editor removes posts, reviews, or content that is deemed offensive after it has been placed on the site or list. In the proactive mode, an editor must review all contributions before they are made public.
In a moderated setting, credibility is often given to the moderator. However, that credibility can be damaged by appearing to edit in a heavy-handed way, whether reactive or proactive (as experienced by digg.com). In an unmoderated setting, credibility lies with the contributors alone. It should be noted that the very existence of an architecture allowing moderation may lend credibility to the forum being used (as in Howard Rheingold's examples from the WELL), or it may take away credibility (as in corporate web sites that post feedback, but edit it highly).
Business Culture

E-Business:
Subsets
Applications can be divided into three categories:
Internal business systems:
customer relationship management
enterprise resource planning
document management systems
human resources management
Enterprise communication and collaboration:
VoIP
content management system
e-mail
voice mail
Web conferencing
Digital work flows (or business process management)
electronic commerce - business-to-business electronic commerce (B2B) or business-to-consumer electronic commerce (B2C):
internet shop
supply chain management
online marketing
offline marketing
Models
When organizations go online, they have to decide which e-business models best suit their goals. A business model is defined as the organization of product, service and information flows, and the source of revenues and benefits for suppliers and customers. The concept of e-business model is the same but used in the online presence. The following is a list of the currently most adopted e-business models:
E-shops
E-commerce
E-procurement
E-malls
E-auctions
Virtual Communities
Collaboration Platforms
Third-party Marketplaces
Value-chain Integrators
Value-chain Service Providers
Information Brokerage
Telecommunication
Classification by provider and consumer
Roughly dividing the world into providers/producers and consumers/clients one can classify e-businesses into the following categories:
business-to-business (B2B)
business-to-consumer (B2C)
business-to-employee (B2E)
business-to-government (B2G)
government-to-business (G2B)
government-to-government (G2G)
government-to-citizen (G2C)
consumer-to-consumer (C2C)
consumer-to-business (C2B)
Types of Internet Connections (Modes of connecting to the internet)

Technology is developing rapidly and methods for connecting to the Internet change almost daily. In the Ithaca area, the following types of connections are most commonly available:
1. Cable: a cable data connection transfers information from the Internet to your computer and from your computer to the network, through your cable television connection. Cable connections provide high speeds of data transfer downstream, from the Internet to your computer, but are slower when sending data from your computer to the network. Additionally, the number of subscribers online affects transfer rates simultaneously. All connections originate on one line per street, so signals degrade as more subscribers come online. Cable connections can be used by individual subscribers to connect one computer to one line, or can be used to connect multiple computers in a building to the Internet.
2. Dial-up: data is transmitted through an analog phone connection. You connect to the Internet by using your phone line to dial into an ISP’s line. An analog connection is the slowest type of connection available, and will not permit you to use your telephone for a voice connection at the same time that you are connected to the Internet. Dial-up connections allow only one computer at a time, per line, to be connected. Cornell offers the EZ-Remote dial-up service.
3. Direct connection: Cornell Information Technologies (CIT) can provide a direct connection depending on your location. In locations where CIT can provide service, the connection is made via fiber optic cabling from the site to the Cornell University network backbone and then to CIT installed, owned and maintained network electronics. Connections are typically 10 Mbps or 100 Mbps; however, Gigabit connections are available at an additional cost.
4. DSL (Digital Subscriber Line): DSL and its variations (such as ADSL - Asymmetric Digital Subscriber Line), use normal phone lines to transmit and receive data digitally. Unlike a cable connection, DSL allows you exclusive use of the line – there is no signal degradation caused by other users. Like cable connections, DSL offers high-speed connectivity, and allows you to use your phone and be online at the same time. DSL can be used for individuals who want to connect one computer to one line, or for an extra investment DSL can be used to connect a building to the Internet.
5. ISDN (Integrated Services Digital Network): ISDN is a slightly older technology that also provides a high-speed connection. ISDN offers connections over ordinary telephone wire, facilitating both voice and data transmission so you can maintain your connection to the Internet while placing telephone calls. ISDN can be used for individuals who need to connect one computer to one line, or can be used to connect multiple computers in a building to the Internet.
6. T1: is a digital transmission technology that uses copper wire. T1 could be used to provide data service to an entire building, and data wiring would distribute the service throughout the building. T1 is the technology used on the Cornell campus. A T1 connection requires a substantial investment and because of this, may not be the most desirable means of connecting your house.
7. Wireless: is a high-speed technology that transmits data over radio waves. Wireless transmission can be used to provide connectivity from an ISP to an entire building, however, service will be dependent on the existence of a clear line of sight between the ISP and the building. Within a building, a wireless local area network (LAN) can connect multiple computers to each other and to the Internet. Wireless is a technology that is continually developing.
Internet service provider

Internet service provider (ISP, also called Internet access provider or IAP) is a company that offers their customers access to the Internet. The ISP connects to its customers using a data transmission technology appropriate for delivering Internet Protocol datagrams, such as dial-up, DSL, cable modem or dedicated high-speed interconnects.
ISPs may provide Internet e-mail accounts to users which allow them to communicate with one another by sending and receiving electronic messages through their ISPs' servers. ISPs may provide other services such as remotely storing data files on behalf of their customers, as well as other services unique to each particular ISP.
End-User-to-ISP Connection
ISPs employ a range of technologies to enable consumers to connect to their network.
For home users and small businesses, the most popular options include dial-up, DSL (typically Asymmetric Digital Subscriber Line, ADSL), broadband wireless, cable modem, fiber to the premises (FTTH), and Integrated Services Digital Network (ISDN) (typically basic rate interface).
For customers with more demanding requirements, such as medium-to-large businesses, or other ISPs, DSL (often SHDSL or ADSL), Ethernet, Metro Ethernet, Gigabit Ethernet, Frame Relay, ISDN (BRI or PRI), ATM, satellite Internet access and synchronous optical networking (SONET) are more likely to be used.
With the increasing popularity of downloading music and online video and the general demand for faster page loads, higher bandwidth connections are becoming more popular.[citation needed]
Typical home user connection
DSL
Broadband wireless access
Cable Internet
ISDN
WiFi
1. DSL, is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop, although in recent years, the term digital subscriber line has been widely adopted as a more marketing-friendly term for ADSL, which is the most popular version of consumer-ready DSL. DSL can be used at the same time and on the same telephone line with regular telephone, as it uses high frequency, while regular telephone uses low frequency.
Typically, the download speed of consumer DSL services ranges from 256 kilobits per second (kbit/s) to 24,000 kbit/s, depending on DSL technology, line conditions and service level implemented. Typically, upload speed is lower than download speed for Asymmetric Digital Subscriber Line (ADSL) and equal to download speed for the rarer Symmetric Digital Subscriber Line (SDSL).
2. Wireless Broadband is a fairly new technology that provides high-speed wireless internet and data network access over a wide area.
According to the 802.16-2004 standard, broadband means 'having instantaneous bandwidth greater than around 1 MHz and supporting data rates greater than about 1.5 Mbit/s. This means that Wireless Broadband features speeds roughly equivalent to wired broadband access, such as that of ADSL or a cable modem.
3. In telecommunications, cable Internet is a form of broadband Internet access that uses the cable television infrastructure.
Like digital subscriber lines and fiber optic networks, cable Internet bridges the last kilometre or mile from the Internet provider to the subscriber. It is layered on top of the existing cable television network infrastructure; just as DSL uses the existing telephone network. Cable networks and telephone networks are the two predominant forms of residential Internet access. Recently, both have seen increased competition from fiber deployments, wireless, and mobile networks.
4. Integrated Services Digital Network(ISDN) is a telephone system network. Prior to the ISDN, the phone system was viewed as a way to transport voice, with some special services available for data. The key feature of the ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system. There are several kinds of access interfaces to the ISDN defined: Basic Rate Interface (BRI), Primary Rate Interface (PRI) and Broadband-ISDN (B-ISDN).
ISDN is a circuit-switched telephone network system, that also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better voice quality than an analog phone. ISDN B-channels can be bonded to achieve a greater data rate, typically 3 or 4 BRIs (6 to 8 64 kbit/s channels) are bonded.
5. Wi-Fi is a trademark of the Wi-Fi Alliance, founded in 1999 as WECA (Wireless Ethernet Compatibility Alliance). The organisation comprises more than 300 companies, whose products are certified by the Wi-Fi Alliance, based on the IEEE 802.11 standards (also called WLAN (Wireless LAN) and Wi-Fi). This certification warrants interoperability between different wireless devices.
A Wi-Fi enabled device such as a PC, game console, mobile phone, MP3 player or PDA can connect to the Internet when within range of a wireless network connected to the Internet. Wi-Fi technology has served to set up mesh networks.

Typical business type connection
DSL
SHDSL
Ethernet technologies
· Single-pair High-speed Digital Subscriber Line (SHDSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. Compared to ADSL, SHDSL employs frequencies that include those used by traditional POTS (Plain old telephone service) telephone services to provide equal transmit and receive (i.e. symmetric) data rates. As such, a frequency splitter, or microfilter, can not be used to allow a telephone line to be shared by both an SHDSL service and a POTS service at the same time. Support of symmetric data rates has made SHDSL a popular choice by businesses for PBX, VPN, web hosting and other data services.
· Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether(medium that carries light). It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model, through means of network access at the Media Access Control (MAC) /Data Link Layer, and a common addressing format.
Ethernet is standardized as IEEE 802.3. The combination of the twisted pair versions of Ethernet for connecting end systems to the network, along with the fiber optic versions for site backbones, is the most widespread wired LAN technology. It has been in use from around 1980[1] to the present, largely replacing competing LAN standards such as token ring, FDDI, and ARCNET.



ISP Interconnection
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 and/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.

Services provided by ISP’s:
1. Broadband Internet access
· Fixed wireless access
· Cable
· Triple play
2. Internet hosting service
· Web hosting service
· E-mail hosting service
· DNS hosting service
3. Dynamic DNS
1. Broadband Internet access, often shortened to just broadband, is high data rate Internet access—typically contrasted with dial-up access over a modem.
Dial-up modems are generally only capable of a maximum bitrate of 56 kbit/s (kilobits per second) and require the full use of a telephone line—whereas broadband technologies supply at least double this bandwidth and generally without disrupting telephone use.
Technology used:
The standard broadband technologies in most areas are DSL and cable modems. Newer technologies in use include VDSL(Very High Bitrate DSL) and pushing optical fiber connections closer to the subscriber in both telephone and cable plants. Fiber-optic communication, while only recently being used in fiber to the premises and fiber to the curb schemes, has played a crucial role in enabling Broadband Internet access by making transmission of information over larger distances much more cost-effective than copper wire technology. In a few areas not served by cable or ADSL, community organizations have begun to install Wi-Fi networks, and in some cities and towns local governments are installing municipal Wi-Fi networks.
Broadband implementations and standards
Digital Subscriber Line (DSL), digital data transmission over the wires used in the local loop of a telephone network
Local Multipoint Distribution Service, broadband wireless access technology that uses microwave signals operating between the 26 GHz and 29 GHz bands
WiMAX, a standards-based wireless technology that provides high-throughput broadband connections over long distances
Satellite Internet access
Cable modem, designed to modulate a data signal over cable television infrastructure
Fiber to the premises, based on fiber-optic cables and associated optical electronics
High-Speed Packet Access (HSPA), a new mobile telephony protocol, sometimes referred to as a 3.5G (or "3½G") technology
Evolution-Data Optimized (EVDO), is a wireless radio broadband data standard adopted by many CDMA mobile phone service providers
2. An Internet hosting service is a service that runs Internet servers, allowing organizations and individuals to serve content to the Internet. There are various levels of service and various kinds of services offered.
A common kind of hosting is web hosting. Most hosting providers offer a combined variety of services. Web hosting services also offer e-mail hosting service, for example. DNS hosting service is usually bundled with domain name registration.
Following are some Internet hosting services:
· Web hosting service is a type of Internet hosting service that allows individuals and organizations to provide their own website accessible via the World Wide Web. Web hosts are companies that provide space on a server they own for use by their clients as well as providing Internet connectivity, typically in a data center. Web hosts can also provide data center space and connectivity to the Internet for servers they do not own to be located in their data center, called colocation.
· An email hosting service is an Internet hosting service that runs email servers.
Email hosting services usually offer premium email at a cost as opposed to advertising supported free email or free webmail.
Email hosting services thus differ from typical end-user email providers such as webmail sites. They cater mostly to demanding email users and Small and Mid Size (SME) businesses, while larger enterprises usually run their own email hosting service. Email hosting providers allow for premium email services along with custom configurations and large number of accounts. In addition, hosting providers manage user's own domain name, including any email authentication scheme that the domain owner wishes to enforce in order to convey the meaning that using a specific domain name identifies and qualifies email senders.
· A DNS hosting service is a service that runs Domain Name System servers. Most, but not all, domain name registrars include DNS hosting service with registration. Free DNS hosting services also exist. Almost all DNS hosting services are "shared"; except for the most popular Internet sites, there is no need to dedicate a server to hosting DNS for a single website. Many third-party DNS hosting services provide Dynamic DNS.
DNS hosting service is better when the provider has multiple servers in various geographic locations that minimize latency for clients around the world.
DNS can also be self-hosted by running DNS software on generic Internet hosting services.
3. Dynamic DNS is a method, protocol, or network service that provides the capability for a networked device using the Internet Protocol Suite, such as an IP router or computer system, to notify a domain name server to change, in real time (ad-hoc) the active DNS configuration of its configured hostnames, addresses or other information stored in DNS.
numerous providers, called Dynamic DNS service providers, offer such technology and services on the Internet. They provide a software client program that automates this function. The client program is executed on a computer or device in the private network. It connects to the service provider's systems and causes those systems to link the discovered public IP address of the home network with a hostname in the domain name system. Depending on the provider, the hostname is registered within a domain owned by the provider or the customer's own domain name. These services can function by a number of mechanisms. Often they use an HTTP service request since even restrictive environments usually allow HTTP service. This group of services is commonly also referred to by the term Dynamic DNS, although it is not the standards-based DNS Update method. However, the latter might be involved in the providers systems.




ISPs having all-India license include:
BSNL
CMC
RPG Infotech
Essel Shyam Communications
Sify
Siti Cable Network
Gateway Systems (India)
World Phone Internet Services
VSNL
Guj Info Petro
Hughes Escorts Communications
Astro India Networks
Reliance
Primus Telecommunications India
ERNET India
RailTel Corporation
Data Infosys
GTL
Jumpp India
L&T Finance
HCL Infinet
Primenet Global
Tata Internet Services
Tata Power Broadband
Bharti Infotel
Pacific Internet India
In2Cable (India)
Reliance Engineering Associates
BG Broad India
Swiftmail Communications
Estel Communication
Bharti Aquanet
Trak Online Net India
Spectra Net
Reach Network India
i2i Enterprise
Tata Teleservices (Maharashtra)
Comsat Max
Gujarat Narmada Valley Fertilizers Corporation
HCL Comnet Systems and Services
Harthway Cable


Internet Addressing

Each computer on the Internet has a numerical address, called an IP address. Because the numbers are hard to remember, popular servers on the Internet have names associated with their numbers. These names are known as domain names.
There are several parts to an internet name:
Top Level Domain (TLD)
This is the last part of the name. It can be .com for companies, .org for non profit organizations, .net for network infrastructure providers, .edu for educational institutions, .mil for military, .gov for government, or a code for a country, for example, .us for United States or .jp for Japan.
Domain Name
This is the middle part of the name and often the most important. It is specific to the company / organization. Example: google, yahoo, onion.
Host Name
This is the name of the server within the company, usually named after the service provided. Example: www, ftp, news, mail.
Method/Scheme
This is the method used for the communication. It is usually a few letters followed by a colon and two forward slashes. Example: http:// for web connections, ftp:// for ftp connections.
So a complete example is:
http://people.yahoo.com
In the above example,
· http:// is the scheme indicating that this is a web connection.
· people is the server name, indicating something to do with people (in this case, finding them).
· yahoo is the domain name, indicating that this people searching functionality is provided by the company Yahoo!.
· com is the top level domain, indicating that Yahoo! is a company.

IP Addresses


An Internet Protocol (IP) address is a numerical identification (logical address) that is assigned to devices participating in a computer network utilizing the Internet Protocol for communication between its nodes.

Format:

An IP address is made up of four bytes of information (totaling 32 bits) expressed as four numbers between 0 and 255 shown separated by periods. For example, your computer's IP address might be 238.17.159.4, which is shown below in human-readable decimal form and in the binary form used on the Internet.

Example IP Address
Decimal:
238 . 17 . 159 . 4
Binary:
11101110 00010001 10011111 00000100
Each of the four numbers uses eight bits of storage, and so can represent any of the 256 numbers in the range between zero (binary 00000000) and 255 (binary 11111111). Therefore, there are more than 4 billion possible different IP addresses in all:
4,294,967,296 = 256 * 256 * 256 * 256

Private And Public IP Addresses

A computer on the Internet is identified by its IP address. In order to avoid address conflicts, IP addresses are publicly registered with the Network Information Centre (NIC). Computers on private TCP/IP LANs however do not need public addresses, since they do not need to be accessed by the public. For this reason, the NIC has reserved certain addresses that will never be registered publicly. These are known as private IP addresses, and are found in the following ranges:
From 10.0.0.0 to 10.255.255.255From 172.16.0.0 to 172.31.255.255From 192.168.0.0 to 192.168.255.255


Classes of IP addresses
The four octets that make up an IP address are conventionally represented by a, b, c, and d respectively. The following table shows how the octets are distributed in classes A, B, and C.
Class
IP Address
Network ID
Host ID
A
a.b.c.d
a
b.c.d
B
a.b.c.d
a.b
c.d
C
a.b.c.d
a.b.c
D
D
a.b.c.d
Multicast Addresses
E
a.b.c.d
Reserved for future use

Class A - 0nnnnnnn hhhhhhhh hhhhhhhh hhhhhhhh
· First bit 0; 7 network bits; 24 host bits
· Initial byte: 0 - 127
· 126 Class As exist (0 and 127 are reserved)
· 16,777,214 hosts on each Class A
Class B - 10nnnnnn nnnnnnnn hhhhhhhh hhhhhhhh
· First two bits 10; 14 network bits; 16 host bits
· Initial byte: 128 - 191
· 16,384 Class Bs exist
· 65,532 hosts on each Class B
Class C - 110nnnnn nnnnnnnn nnnnnnnn hhhhhhhh
· First three bits 110; 21 network bits; 8 host bits
· Initial byte: 192 - 223
· 2,097,152 Class Cs exist
· 254 hosts on each Class C
Class D - 1110mmmm mmmmmmmm mmmmmmmm mmmmmmmm
· First four bits 1110; 28 multicast address bits
· Initial byte: 224 - 247
· Class Ds are multicast addresses
Class E - 1111rrrr rrrrrrrr rrrrrrrr rrrrrrrr
· First four bits 1111; 28 reserved address bits
· Initial byte: 248 - 255
· Reserved for experimental use
IP versions
The Internet Protocol (IP) has two versions currently in. Each version has its own definition of an IP address. Because of its prevalence, "IP address" typically refers to those defined by IPv4.
1. IP version 4 addresses( IPv4)
IPv4 uses 32-bit (4-byte) addresses, which limits the address space to 4,294,967,296 (232) possible unique addresses. However, IPv4 reserves some addresses for special purposes such as private networks (~18 million addresses) or multicast addresses (~270 million addresses). This reduces the number of addresses that can be allocated as public Internet addresses, and as the number of addresses available is consumed, an IPv4 address shortage appears to be inevitable in the long run. This limitation has helped stimulate the push towards IPv6, which is currently in the early stages of deployment and is currently the only offering to replace IPv4.
IPv4 addresses are usually represented in dotted-decimal notation (four numbers, each ranging from 0 to 255, separated by dots, e.g. 208.77.188.166). Each part represents 8 bits of the address, and is therefore called an octet. It is possible, although less common, to write IPv4 addresses in binary or hexadecimal. When converting, each octet is treated as a separate number. (So 255.255.0.0 in dot-decimal would be FF.FF.00.00 in hexadecimal.)
IPv4 networks
IP address as a structure of network number and host number.
The highest order octet (most significant eight bits) were designating the network number, and the rest of the bits were called the rest field or host identifier and used for host numbering within a network.
This method soon proved inadequate as local area networks developed that were not part of the larger networks already designated by a network number. In 1981, the Internet addressing specification was revised with the introduction of classful network architecture. [2]
Classful network design allowed for a larger number of individual assignments. The first three bits of the most significant octet of an IP address was defined as the "class" of the address, instead of just the network number and, depending on the class derived, the network designation was based on octet boundary segments of the entire address. The following table gives an overview of this system.
Class
First octet in binary
Range of first octet
Network ID
Host ID
Possible number of networks
Possible number of hosts
A
0XXXXXXX
0 - 127
a
b.c.d
128 = (27)
16,777,214 = (224 - 2)
B
10XXXXXX
128 - 191
a.b
c.d
16,384 = (214)
65,534 = (216 - 2)
C
110XXXXX
192 - 223
a.b.c
d
2,097,152 = (221)
254 = (28 - 2)
IPv4 private addresses
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 ranges of IPv4 addresses for private networks, one range for each class (A, B, C). These addresses are not routed on the Internet, and thus need not be coordinated with an IP address registry.
IANA Reserved Private Network Ranges
Start of range
End of range
Total addresses
24-bit Block (/8 prefix, 1 x A)
10.0.0.0
10.255.255.255
16,777,216
20-bit Block (/12 prefix, 16 x B)
172.16.0.0
172.31.255.255
1,048,576
16-bit Block (/16 prefix, 256 x C)
192.168.0.0
192.168.255.255
65,536
Any user may use any block. 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 - 192.168.0.255 (192.168.0.0/24).
IPv4 address depletion
The IP version 4 address space is rapidly nearing exhaustion of available, officially assignable address blocks.
2. IP version 6 addresses( IPv6)
The rapid exhaustion of IPv4 address space, despite conservation techniques, prompted the Internet Engineering Task Force (IETF) to explore new technologies to expand the Internet's addressing capability. The permanent solution was deemed to be a redesign of the Internet Protocol itself. This next generation of the Internet Protocol, aimed to replace IPv4 on the Internet, was eventually named Internet Protocol Version 6 (IPv6). The address size was increased from 32 to 128 bits (16 bytes), which, even with a generous assignment of network blocks, is deemed sufficient for the foreseeable future. Mathematically, the new address space provides the potential for a maximum of 2128, or about 3.403 × 1038 unique addresses.
Example of an IPv6 address:2001:0db8:85a3:08d3:1319:8a2e:0370:7334


IP subnetworks

The technique of subnetting can operate in both IPv4 and IPv6 networks. The IP address is divided into two parts: the network address and the host identifier. The subnet mask (in IPv4 only) or the CIDR prefix determine 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 Classless Inter-Domain Routing (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.
Static and dynamic IP addresses
When a computer is configured to use the same IP address each time it powers up, this is known as a Static IP address. In contrast, in situations when the computer's IP address is assigned automatically, it is known as a Dynamic IP address.
Method of assignment
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 randomly, 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, and never to assign that IP address to another computer. This allows static IP addresses to be configured in one place, without having to specifically configure each computer on the network in a different way.
In the absence of both an administrator (to assign a static IP address) and a DHCP server, the operating system may assign itself an IP address using state-less autoconfiguration methods. These IP addresses, known as link-local addresses, default to the 169.254.0.0/16 address range in IPv4.
In IPv6, every interface, whether using static or dynamic address assignments, also receives a local-link address automatically in the fe80::/64 subnet.
Advantage of using dynamic addressing
Dynamic IP addresses are most frequently assigned on LANs and broadband networks by Dynamic Host Configuration Protocol (DHCP) servers. 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 assigning dynamic IP addresses. Dialup and some broadband networks use dynamic address features of the Point-to-Point Protocol.



Domain names


The most basic functionality of a domain name is to provide symbolic representations, i.e., recognizable names, to mostly numerically addressed Internet resources. This abstraction allows any resource (e.g., website) to be moved to a different physical location in the address topology of the network, globally or locally in an intranet, in effect changing the IP address. This translation from domain names to IP addresses (and vice versa) is accomplished with the global facilities of Domain Name System (DNS).
Examples
The following example illustrates the difference between a URL (Uniform Resource Locator) and a domain name:
URL: http://www.example.net/index.html
Domain name: www.example.net
Registered domain name: example.net
virtual hosting
As a general rule, the IP address and the server name are interchangeable. For most Internet services, the server will not have any way to know which was used. However, the explosion of interest in the Web means that there are far more Web sites than servers. To accommodate this, the hypertext transfer protocol (HTTP) specifies that the client tells the server which name is being used. This way, one server with one IP address can provide different sites for different domain names. This feature goes under the name virtual hosting and is commonly used by Web hosts.
For example, as referenced in RFC 2606 (Reserved Top Level DNS Names), the server at IP address 208.77.188.166 handles all of the following sites:
example.com
www.example.com
example.net
www.example.net
example.org
www.example.org
When a request is made, the data corresponding to the hostname requested is provided to the user.


Top-level domains
Every domain name ends in a top-level domain (TLD) name, which is always either one of a small list of generic names (three or more characters), or a two-character territory code. Top-level domains are sometimes also called first-level domains.
Following typre of TLDs are there:
1. Country code top-level domain (ccTLD)
2. Generic top-level domain (gTLD)
1. A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country or a dependent territory.
All ccTLD identifiers are two letters long, and all two-letter top-level domains are ccTLDs. Creation and delegation of ccTLDs is performed by the Internet Assigned Numbers Authority (IANA).
Examples:
.ae – United Arab Emirates
.at – Austria *
.au – Australia
.be – Belgium *
.br – Brazil *
.ca – Canada
.cy – Cyprus
.de – Germany
.fr – France
.it – Italy
.jp – Japan
.lk – Sri Lanka
.mu – Mauritius *
.mv – Maldives
.mx – Mexico *
.my – Malaysia
.ng – Nigeria
.nl – Netherlands *
.nz – New Zealand *
.pk – Pakistan *
.sa – Saudi Arabia
.th – Thailand *
.us – United States *
.za – South Africa *
.zw – Zimbabwe

2. A generic top-level domain (gTLD) is one of the categories of top-level domains (TLDs) maintained by the Internet Assigned Numbers Authority (IANA) for use on the Internet.

gTLD
Entity
.aero
air-transport industry
.asia
Asia-Pacific region
.biz
business
.cat
Catalan
.com
commercial
.coop
cooperatives
.edu
educational
.gov
governmental
.info
information
.int
international organizations
.jobs
companies
.mil
U.S. military
.mobi
mobile devices
.museum
museums
.name
individuals, by name
.net
network
.org
organization
.pro
professions
.tel
Internet communication services
.travel
travel and tourism industry related sites


Domain aftermarket prices and trends
Domain name sales occurring in the aftermarket are frequently submitted to the DN journal. The sales are listed weekly and include the top aftermarket resellers which include but are not limited to Sedo, Traffic (auctions), Afternic, NameJet, Moniker and private sales.
To date, and according to Guinness World Records and MSNBC, the most expensive domain name sales on record as of 2004 were[3]:
Business.com for $7.5 million in December 1999
AsSeenOnTv.com for $5.1 million in January 2000
Altavista.com for $3.3 million in August 1998
Wine.com for $2.9 million in September 1999
CreditCards.com for $2.75 million in July 2004
Autos.com for $2.2 million in December 1999
The week ending January 27, 2008, DNJournal reported that CNN, a cable news channel purchased iReport.com for $750,000. This signifies another turning point in domain name sales. This name has neither organic traffic, nor does it have a dictionary term alone. Instead it is a highly brandable domain name utilizing the second most popular prefix for a "dictionary" and commercial word.



Communication software

Communication software is used to provide remote access to systems and exchange files and real-time messages in text, audio and/or video formats between different computers or user IDs. This includes terminal emulators, file transfer programs, chat and instant messaging programs, as well as similar functionality integrated within MUDs.
In computer gaming, a MUD (Multi-User Dungeon), pronounced /mʌd/, is a multi-user real-time virtual world described entirely in text. It combines elements of role-playing games, hack and slash, interactive fiction, and online chat. Players can read descriptions of rooms, objects, other players, non-player characters, and actions performed in the virtual world. Players interact with each other and the world by typing commands that resemble a natural language.
Traditional MUDs implement a fantasy world populated by fictional races and monsters, with players being able to choose from a number of classes in order to gain specific skills or powers. The object of this sort of game is to slay monsters, explore a fantasy world, complete quests, go on adventures, create a story by roleplaying, and advance the created character. Many MUDs were fashioned around the dice rolling rules of the Dungeons & Dragons series of games.


INTERNET TOOLS

NETWORK INFORMATION RETRIEVAL (NIR) TOOLS
Utilities
Finger
Definition: Finger retrieves information about user registered on a host computer.
Netfind
Definition: Netfind is a research prototype that provides a simple Internet `white pages' user directory.
Nslookup
Definition: Nslookup is an interactive program to query Internet domain name servers (gives IP address).
Ping
Definition: Ping requests echo from network host; see if remote host is up.
WHOIS
Definition: WHOIS provides info on registered network names.
X.500
Definition: X.500 (OSI Directory Service) provides globally distributed directory service.
Tools
Archie
Definition: Archie locates files at anonymous FTP sites by filename search.
Astra
Definition: Astra retrieve documents from databases.
Bitftp
Definition: Bitftp allows the user to use electronic mail to obtain files at an ftp site via email.
Essence
Definition: Essence is a resource discovery system using indexes.
File Service Protocol (FSP)
Definition: FSP is a conectionaless protocol for transferring files.
File Transfer Protocol (FTP)
Definition: FTP retrieves or puts copies of files at remote FTP sites.
Knowbot
Definition: Knowbot provides a uniform interface to heterogeneous remote directory services.
Netserv
Definition: Netserv is a server for access to data files and programs of general interest.
Soft Pages
Definition: Soft Pages aids in retrieval of documents, software, and other resources from servers.
Telnet
Definition: Telnet allows a user to login to a remote computer to use applications.
Veronica
Definition: Veronica locates titles of Gopher items by keyword search.
Systems
Alex
Definition: Alex provides transparent read of remote files at anonymous FTP sites.
Gopher
Definition: Gopher locates and retrieves resources using a graph of menus.
Moo Gopher
Definition: Moo Gopher is a MUD-based gopher interface.
Wide Area Information Server (WAIS)
Definition: WAIS retrieves resources by searching indexes of databases.
World Wide Web (WWW)
Definition: WWW retrieves resources by hyptertext browser of databases.
Interfaces
Lists
For a longer list of World Wide Web broswers, see:
Cello
Definition: Cello is a DOS-based Internet browser incorporating WWW, Gopher, FTP, Telnet, News.
Emacs World Wide Web Browser
Definition: Emacs WWW browser is a means to access the World Wide Web.
Lynx
Definition: Lynx is an ASCII terminal browser for the World Wide Web.
Samba
Definition: Samba is a Macintosh browser for the World Wide Web.
Viola
Definition: Viola is a World Wide Web hypermedia browser for X Window System.
COMPUTER-MEDIATED COMMUNICATION (CMC) FORUMS
Interpersonal
Email
Definition: Email allows a user to send message(s) to another user (or many users via mailing lists).
Talk
Definition: Talk provides real-time interactive text with another user.
Group
Clover
Definition: Clover is a real-time text-based group conferencing system.
Collage
Definition: Collage is a client/server group collaboration system which includes shared dialogue, text, and graphics spaces, from NCSA.
CU-SeeMe
Definition: CU-SeeMe is a real-time, multiparty video-conferencing system for the Internet.
Listproc
Defintion: Listproc is a system that automates mailing lists and archives.
LISTSERV
Definition: LISTSERV is mailing-list server for group communication.
Majordomo
Definition: Majordomo is a mailing list manager.
Moo
Definition: A Moo is an object-oriented Multiple User Dialogue (MUD).
Multiple-User Dialogue (MUD)
Definition: MUDs are real-time interaction usually for social role-playing. Note: Variants include MUCK, MUSH, MUSE, MOO.
Procmail
Definition: Procmail is a mail manager--create mail-servers, mailing lists, sort your incoming mail.
Mass
Interactive Webbing (IW)
Definition: Interactive Webbing gives people a common space for network distributed multimedia writing.
Internet Relay Chat (IRC)
Definition: IRC provides real-time, many-many text discussion divided into channels.
Internet Talk Radio (ITR)
Definition: ITR is an audio multicast on the Internet.
Mbone
Definition: Mbone is a live audio and video multicast virtual network on top of Internet.
Usenet
Definition: USENET provides asynchronous text discussion on many topics separated into newsgroups.