What Is INTERNET? Part 1

The Internet is a massive public spiderweb of computer connections

•   Packet of information flow between machines governed by common rules (protocols):
    –Internet protocol (IP)
    –Transport control protocol (TCP)
•   Internet is a packet-switching network
    –Messages are decomposed into packets, containing part of the message, plus information on the sending         and receiving machines and how the packet relates to the other packets
    –Packets travel independently and possibly on different routes through the Internet
      Packets are reassembled into the message at the receiving

What are protocols?

·       (Internet Protocol) is the primary network protocol used on the Internet, developed in the 1970s. On the Internet and many other networks, IP is often used together with the Transport Control Protocol (TCP) and referred to interchangeably as TCP/IP.

·     The Internet Protocol is responsible for addressing hosts and routing datagrams (packets) from a source host to a destination host across one or more IP networks. For this purpose the Internet Protocol defines the format of packets and an addressing system that has two functions: identifying hosts and providing a logical location service.

What is TCP/IP?

·       TCP/IP pronounced as separate letters) Short for Transmission Control Protocol/Internet Protocol, the suite of communications protocols used to connect hosts on the Internet. TCP/IP uses several protocols, the two main ones being TCP and IP. TCP/IP is built into the UNIX operating system and is used by the Internet, making it the de facto standard for transmitting data over networks. Even network operating systems that have their own protocols, such as Netware, also support TCP/IP.

·      The information is called Hypertext documents commonly known as HTML ( Hypertext Markup Language) This includes text and codes, which are visible only to the web browser and instruct the browser how to display the text. For example ,<b> help </b> would appear as help.

How does information travel trough the Internet?

-Data is divided up into packets

-Data routes across the Internet can be switched to avoidcongestion

-Entire mechanism is handled by the TCP/IP protocols

1. The Internet is based on packet-switched protocols. Information is carried in packets, which can be imagined as small parcels being passed from computer to computer.

2. The protocol, that is used to encode the packet ensures safe transit, and provides a way of reconstructing the data when it reaches its destination. The protocols used on the Internet are referred to as TCP/IP, standing for Transmission Control Protocol / Internet Protocol.

3. As a switched network, the physical connections between computers do not matter as far as Internet traffic is concerned

4. The protocols ensure that guaranteed information delivery is more important than speed or use of a particular route. This means that a sequence of packets might arrive out of order, with some travelling through the net by a faster, shorter route than others.

5. TCP/IP provides the means for your software to piece together those packets into meaningful data. The ability to take different routes through the network is a fundamental part of the original design of TCP/IP, as it allows the Internet to route around damaged areas of the network.     

   
   
   
   

   How does the connection works from home?

   
   

   ·         Modems and routers

   
   

   
   

   
   

   

   
   

   
   

   
   

   ·         Negotiating a connection

   To connect from home you need several things. Apart from a computer (obviously!) you'll need a phone connection, a modem or ADSL router, and some Internet software. Things will be easier if you're using a relatively recent operation system, such as Windows Vista/XP or MacOSX, but it's possible to connect with older or more obscure systems.

   With a modem and the appropriate software, you can dial up another modem connected to another computer, and establish a network connection with it. Usually, this computer is linked into the Internet, and so you're online.

   With an ADSL modem or router, a similar procedure happens, but a filter splits the telephone line into voice and data (low and high frequencies) and your router negotiates a connection with the ADSL equipment in the telephone exchange. 
   
   

   Figure 1.2. ADSL Frequency Spectrum

   Frequencies used on an ADSL line: PSTN is the normal telephone ("voice") usage, and the upstream/downstream areas are for data. Note the unequal proportions of the data range (i.e. Assymetric DSL)
   
   
   ·         Short for Internet Service Provider, it refers to a company that provides Internet services, including personal and business access to the Internet. For a monthly fee, the service provider usually provides a software package, username, password and access phone number. Equipped with a modem, you can then log on to the Internet and browse the World Wide Web and USENET, and send and receive e-mail. For broadband access you typically receive the broadband modem hardware or pay a monthly fee for this equipment that is added to your ISP account billing.
   
   
   ·         In addition to serving individuals, ISPs also serve large companies, providing a direct connection from the company's networks to the Internet. ISPs themselves are connected to one another through Network Access Points (NAPs). ISPs may also be called IAPs (Internet Access Providers).