What is the Internet?

A network of networks that connects computers all over the world.

The name for a vast, world wide System consisting of people, information, and computers.

Practical or commercial point of view: a vast collection of information that can be search and retrieved electronically.

Technical point of view A network of tens of thousands of computer networks.
Technically, what distinguishes the Internet is its use of a set of protocols called TCP/IP (Transmission Control Protocol/Internet Protocol).

Social point of view a network that allows millions of people throughout out the world to communicate with each other, sending and receiveing messages.

A collection of networks throughout the world that agree to communicate using specific telecommunications protocols, the most basic being the Internet protocol (IP) and transmission control protocol (TCP), and services supplied by those networks.

The Roots of the Internet lie in the project called the ARPANET which was sponsored by the U.S. States Department of Defense Advanced Research Projects. (ARPA)

History of the Internet

Hobbes' Internet Timeline Copyright (c)1993-9 by Robert H Zakon.
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Hobbes' Internet Time Line

The History of the Internet

A Brief History of the Internet

Networks on the Internet

The Internet is a large ``network of networks.'' There is no one network known as The Internet; rather, regional nets like

• SuraNet
• PrepNet
• NearNet,

UUCP

The UUCP network is a loose association of systems all communicating with the UUCP protocol. (UUCP stands for `Unix-to-Unix Copy Program'.)

It's based on two systems connecting to each other at specified intervals, called polling, and executing any work scheduled for either of them.

Most UUCP was done with Unix equipment, although the software has since been implemented on other platforms (e.g. VMS).

BITNET BITNET (the ``Because It's Time Network'') is comprised of systems connected by point-to-point links, all running the NJE protocol.

It's continued to grow, but has found itself suffering at the hands of the falling costs of Internet connections. A number of mail gateways are in place to reach users on other networks.

Network Connections on the Internet

• The most prevalent for Internet links are 56k leased lines (dedicated telephone lines carrying 56kilobit-per-second connections) and T1 links (special phone lines with 1Mbps connections).
• Also installed are T3 links, acting as backbones between major locations to carry a massive 45Mbps load of traffic.

These links are paid for by each institution to a local carrier (for example, Bell Atlantic owns PrepNet, the main provider in Pennsylvania). Also available are SLIP connections, which carry Internet traffic (packets) over high-speed modems.

UUCP links are made with modems (for the most part), that run from 1200 baud all the way up to as high as 38.4Kbps.

The Networks, the connections are of the store-and-forward variety.

The systems do their UUCP traffic over TCP/IP connections, which give the UUCP-based network some blindingly fast ``hops,'' resulting in better connectivity for the network as a whole.

UUCP connections first became popular in the 1970's, and have remained in wide-spread use ever since.

BITNET links mostly take the form of 9600bps modems connected from site to site.

Computers on the Internet

Each computer on the Internet is called a host computer

On the Internet, the term "host" means any computer that has full two-way access to other computers on the Internet.

• A host has a specific number that, together with the network number, forms its unique Internet Protocol (IP) address.
• If you use Point to Point Protocol(PPP) to access your Internet Service Provider(ISP), your computer has a unique IP address while connected to the Internet. and is a host while connected. (a "host" is a node in a network).

Each host computer on the Internet has a unique number, called its IP address

IP address an Internet address in numeric form
Static IP Address-permanent IP address which you use each time you log in
Dynamic IP Address-non-permanent IP address, assigned each time you log in

The current version of IP, IP version 4 (IPv4), defines a 32-bit address

• Made up of a sequence of four numbers separated by periods
• Each number ranges from 0 to 255
• Starting from the left, the numbers on the right identify a specific host computer system
• The smallest address is 0.0.0.0 and the largest is 255.255.255.255
• Scheme allows for 256 to 4th power which means that there are only 232 (4,294,967,296) IPv4 addresses are available
• Example: In the IP address 192.65.245.76
  192.65.245 is the network portion of the address
  76 is the host portion

IP addresses and domain names aren't assigned arbitrarily. An application must be filed with the Network Information Center (NIC), either electronically (to hostmaster@nic.ddn.mil) or via regular mail.

Finding IP Addresses

Domain and Host Names

Host name(domain name) Internet name for a network or computer system. The name consists of a sequence of characters separated by periods.

Domain --the last to parts of the host computers name.
Top-level domain -- the last part of the domain name.
Second-level domain-second-to-last part of the domain

Example www.loc.gov

Domain name	www.loc.gov
Top-level domain	gov
Domain	loc.gov
Second-level domain	loc

www identifies this computer as the Library of Congress's Web server
loc tells you that the server is on the Library of Congress's network
gov the top level domain tells you that the server is part of a government system
Two types of top-level domains

1. Organization domains three letter top-level domain based on type of organization

   com	commercial organization	www.yahoo.com
   edu	educational institution	www. umuc.edu
   gov	government	csab.larc.nasa.gov
   int	international organization
   mil	military	nic.ddn.mil
   net	networking	organization www.laze.net
   org	non-profit organization	gopher.eff.org

   The top-level domain names are administered by IANA and its delegate agencies.
   Domain names are assigned by Network Solutions'InterNIC registration services at http://www.internic.net

2. Geographical Domains two-letter top-level domain based on an abbreviation for a particular country

at      Austria         au      Australia               ca      Canada

fr      France          us      United States           jp      Japan

Geographical domains are assigned by the country where the organization that owns the host computer is located.

Servers, Clients, and Ports

Server-a computer system or program which provides information to other programs called clients

• Mail servers handle incoming and outgoing mail
• Post Office Protocol (POP and POP3) store incoming mail
• Simple Mail Transfer Protocol (SMTP) relay outgoing mail
• Web servers store Web pages and transmit them in response to request from web clients
• FTP servers store files that you can transfer to or from your computer.
• News servers store Usenet newsgroup articles that you can read and send.
• IRC servers act as a switchboard for Internet-based online chats

• E-mail clients get incoming messages from, and send outgoing messages to a mail server, and enable you to read, write, and print messages -pine
• Web clients (browsers) used to access the Web and the Internet resources -Netscape and Internet Explorer

• Mosaic first web client to take advantage of a GUI
• Mosaic fist ran under X Window

• Usenet (newsreader) used to read Usenet articles
• FTP(WS_FTP LE) used to transfer files from one computer to another
• Telnet (Ewan)
• IRC (mIRC) used to allow many people to talk with one another in separate conversation areas called channels

Port Number                          Internet Service

21                                  FTP (file transfer)

23                                  Telnet (remote login)

25                                  SMTP (mail relaying)

80                                  World Wide Web

110                                 POP3(storage of incoming mail)

194                                 IRC 9online chat)

532                                 Usenet newsgroups(discussion 
                                        groups)

Domain Name System (DNS) TCP/IP service translates an address from a domain name to an IP address and vice versa

The domain name system (DNS) is the way that Internet domain names are located and translated into IP (Internet Protocol) addresses.
A domain name is a meaningful and easy-to-remember "handle" for an Internet address.
Developed in 1984

Internet Services

• E-mail-allows users to exchange messages and files electronically
• Mailing lists-an organized system in which messages are sent to a collection of addresses in order to support discussion by mail of a particular topic.
• Usenet newsgroups -a vast, decentralized system of discussion groups
• Online chat - provides a way fro real-time online chatting to occur
• Voice and video conferencing enable two or more people to hear and see each other, share a whiteboard, and share applications
• World Wide Web a distributed system of interlinked pages that include text, pictures. Sound and other information
• File transfer(FTP) used to transfer files from computer to another

PPP AND SLIP

Point-to-Point Protocol (PPP) allows a computer with a modem to make a TCP/IP connection over a phone line

• Point-to-point line directly connects the sending and receiving devices, such as terminal with a central computer.
• PPP account connects your computers right onto the Internet computer temporarily becomes a host Can use a many clients at one time

Internet service providers (ISP) an organization or business offering public access to the Internet, usually using a telephone dial-up connection
Provides unlimited access to the Internet and the World wide Web for a flat monthly fee

UNIX Shell Accounts

• Work is done on remote computer
• Computer not on the Net itself, your computer emulates a terminal
• Processing takes place on a remote computer
• Supports text-base interface, not graphical interface

Shell Account

• Limited to the capabilities of the terminal being emulated
• Terminal emulator will only support a text interface
• Downloaded (copying a file from a distant computer files first go to the
• remote host and extra step is need to copy the file to your computer
• Inconvenient to use multiple client programs

• Access to a Unix computer on the Internet with all the UNIX tools
• Information is received faster because system is text based
• Lynx a Unix text based web client
• Can check e-mail from any Internet connection
• Shell account cheaper that a PPP account

Provide access to databases. electronic meeting places, and the Internet to subscribers equipped with telephone-linked microcomputers
America Online(AOL)-the worlds most popular
CompuServe(CIS)-one of the oldest
Microsoft Network(MSN)
Prodigy-not as popular as the three above

Telephone, Cable, and Satellite Connections

Accessing the Internet via the Telephone System ( Items Needed)

• Computer
• Modem-Acronym for modulator/demodulator--a device that enables a computer to transmit data over telephone lines
• Appropriate software
• a telephone number to use to connect to a remote Internet computer

Modem is a device that allows two computers to communicate over a standard phone line.

Modems take a digital signal, from the computer's serial port, and modulate it into an analog form, so you can send it over the phone line.

This is accomplished by changing the digital information of a computer (which is stored as a series of 0's and 1's known as the binary code) into a tone, or frequency, that can be sent over the phone to another modem.

The hiss you hear when you pick up a phone during a modem connection is this analog form.

The receiving modem will then change the sent tones back to digital information, which can be understood by the receiving computer.

This process gives the modem its name, derived from the two words modulate and demodulate, which describe the two primary functions of a modem.

When you read off a piece of paper to someone over the phone, you're being a modem - converting digital information to an analog form (your voice).

The speed of the modem, is calculated in bits per second, where roughly eight bits equals a character of information. Think of this as a page per second.

There are two types of modems -- internal and external.

1. An internal modem is placed directly into a computer's communications (COM) port, which is located inside the computer.
2. An external modem, is kept outside the computer.

• ISDN stands for "Integrated Service Digital Network
• ISDN consist of hardware and software that allow data to communicated as digital signals over traditional copper-wire telephone lines
• ISDN line provides three channels

  Two B channels and one D channel

  B (bearer)channels carry the bulk of the data

  • Computer connections
  • Voice conversations
  • Fax transmissions

  D (data)channel used to control the ISDN line

  • Used for sending the setup signaling information back and forth between the telephone system and your devices
  • Used to control the B channels
• Transfers data five times as fast as the conventional modem
• Installation could cost $300 dollars or more for installation of software and the purchase of a special ISDN connector box Network terminator for layer 1(NT-1) an a Terminal adapter

• Developed by Bellcore Labs the biggest research consortium in the U.S.

  ADSL is a high-speed digital switching/routing and signal processing technology.--conceived in 1994,

  Asymmetric Digital Subscriber Line. ADSL is a modem technology that transforms ordinary phone lines (also known as "twisted copper pairs") into high-speed digital lines for ultra-fast Internet access.

  ADSL modems push as much data as possible across copper wires by making the best use of available bandwidth.

  ADSL takes advantage of the portion of the bandwidth not used for voice calls.

  Splits the 1 MHz bandwidth into three information channels:

  1. a high-speed downstream channel,
  2. a medium-speed duplex upstream/downstream)channel,
  3. a conventional voice channel.

  Downstream refers to data transmitted from the telephone network to the customer's premises;

  Upstream is data routed from the customer to the network.

  ADSL modems use digital coding techniques to squeeze up to 99% more capacity out of a phone line without interfering with your regular phone services.

  ADLS allows you to simultaneously talk on the phone or send a fax - while surfing the World Wide Web

  ADSL provides speeds up to 8 Mbps downstream (to the user) and up to 1 Mbps upstream, depending upon line length and loop and line conditions.

• Average speed 1.5 megabits per second (Mbps)

Cable Modems carry digital data more than 1000 times faster than plain old telephone system (POTS)

• Cable modems speed is 30-43 Mbps compared to a standard or 33.6 Kbps
• Connects a personal computer to a cable-TV system that offers on line services

Satellite Dishes

• Hughes Network System offers a 36-inch satellite dish call the Convergence Antenna that transmits 15 times faster than a standard high-speed modem
• Users subscribe to the satellite Internet service called DirecPC
• A 90-second animation clip that normally takes an hour to download arrives in less than two minutes
• Cost $650 for the antenna and about $150 a month for unlimited access

• Can you get a flat monthly rate?
• access local phone call
• shell account no charge
• Does the provider have sufficient phone lines?
• What type of accounts does the provider offer?--PPP account
• Does the provider have ISDN and fast modems?
• Can you use any Internet clients you want, or must you use the provider's software?
• Does the service provider offer full Internet access?
• Can you put up your own web page for free?