ICT: Setyembre 2015

Miyerkules, Setyembre 30, 2015

Protocols of the Web

TCP/IP is a family of protocols for communication between computers.

What is TCP/IP?

TCP/IP stands for Transmission Control Protocol / Internet Protocol. It defines how electronic devices (like computers) should be connected over the Internet, and how data should be transmitted between them.

TCP - Transmission Control Protocol

TCP is responsible for breaking data down into small packets before they can be sent over a network, and for assembling the packets again when they arrive.

IP - Internet Protocol

IP takes care of the communication between computers. It is responsible for addressing, sending and receiving the data packets over the Internet.

TCP/IP Protocols For the Web

Web browsers and servers use TCP/IP protocols to connect to the Internet. Common TCP/IP protocols are:

HTTP - Hyper Text Transfer Protocol

HTTP takes care of the communication between a web server and a web browser. HTTP is used for sending requests from a web client (a browser) to a web server, returning web content (web pages) from the server back to the client.

HTTPS - Secure HTTP

HTTPS takes care of secure communication between a web server and a web browser. HTTPS typically handles credit card transactions and other sensitive data.

FTP - File Transfer Protocol

FTP takes care of transmission of files between computers.

IP is Connection-Less

IP is a "connection-less" communication protocol.

IP does not occupy the communication line between two computers. This reduces the need for network lines. Each line can be used for communication between many different computers at the same time.

With IP, messages (or other data) are broken up into small independent "packets" and sent between computers via the Internet. IP is responsible for "routing" each packet to the correct destination.

IP Routers

When an IP packet is sent from a computer, it arrives at an IP router.

The IP router is responsible for "routing" the packet to the correct destination, directly or via another router.

The path the packet will follow might be different from other packets of the same communication. The router is responsible for the right addressing, depending on traffic volume, errors in the network, or other parameters.

Analogy: Communicating via IP is like sending a long letter as a large number of small postcards, each finding its own (often different) way to the receiver.

IP Addresses

IP uses 32 bits, or four numbers between 0 and 255, to address a computer.

IP addresses are normally written as four numbers separated by a period, like this: 192.168.1.50.

Each computer must have an unique IP address before it can connect to the Internet.

Each IP packet must have an address before it can be sent to another computer.

This is an IP address: 192.68.20.50. This might be the same address: www.w3schools.com

This is your IP address: 72.21.93.231

In computer terms, TCP/IP uses 32 bits addressing. It uses 4 bytes. One byte is 8 bits. One byte can contain 256 different values:

00000000, 00000001, 00000010, 00000011, 00000100, 00000101, 00000110, 00000111, 00001000 .......and all the way up to 11111111.

Domain Names

A name is much easier to remember than a 12 digit number.

Names used for TCP/IP addresses are called domain names.

w3schools.com is a domain name.

When you address a web site, like http://www.w3schools.com, the name is translated to a number by a Domain Name Server (DNS).

All over the world, DNS servers are connected to the Internet. DNS servers are responsible for translating domain names into TCP/IP addresses.

When a new domain name is registered together with a TCP/IP address, DNS servers all over the world are updated with this information.

TCP/IP Protocols for Email

E-mail programs use TCP/IP for sending and receiving e-mails. The TCP/IP protocols for email are:

SMTP - Simple Mail Transfer Protocol

SMTP takes care of sending emails. Often emails are sent to an email server (SMTP server), then to other servers, and finally to its destination. SMTP can only transmit pure text. It cannot transmit binary data like pictures, sounds or movies.

MIME - Multi-purpose Internet Mail Extensions

The MIME protocol lets SMTP transmit multimedia files including voice, audio, and binary data across TCP/IP networks. The MIME protocol converts binary data to pure text, before it is sent.

POP - Post Office Protocol

The POP protocol is used by email programs to retrieve emails from an email server. If your email program uses POP, all your emails are downloaded to your email program (also called email client), each time it connects to your email server.

IMAP - Internet Message Access Protocol

The IMAP protocol works much like the POP protocol. The main difference is that the IMAP protocol will not automatically download all your emails each time your email program connects to your email server.

The IMAP protocol allows you to look through your email messages at the email server before you download them. With IMAP you can choose to download your messages or just delete them. This way IMAP is perfect if you need to connect to your email server from different locations, but only want to download your messages when you are back in your office.

Other TCP/IP Protocols

ARP - Address Resolution Protocol

ARP is used by IP to find the hardware address of a computer network card based on the IP address.

BOOTP - Boot Protocol

BOOTP is used for booting (starting) computers from the network.

DHCP - Dynamic Host Configuration Protocol

DHCP is used for allocation of dynamic IP addresses to computers in a network.

ICMP - Internet Control Message Protocol

ICMP takes care of error-handling in the network.

LDAP - Lightweight Directory Access Protocol

LDAP is used for collecting information about users and e-mail addresses from the internet.

NTP - Network Time Protocol

NTP is used to synchronize the time (the clock) between computers.

PPTP - Point to Point Tunneling Protocol

PPTP is used for setting up a connection (tunnel) between private networks.

RARP - Reverse Address Resolution Protocol

RARP is used by IP to find the IP address based on the hardware address of a computer network card.

SNMP - Simple Network Management Protocol

SNMP is used for administration of computer networks.

SSL - Secure Sockets Layer

The SSL protocol is used to encrypt data for secure data transmission.

TLS - Transport Layer Security

The TLS protocol is a newer and more secure version of SSL.

Entertainment in the Internet

Services of the internet

Internet service providers (ISP - Internet Service Provider) companies or institutions (such as T-Com, Iskon or CARNet in Croatia, AT&T in US and MTNL in India), which satellite or optical connections with several major Internet node abroad (mainly in the direction of America and Europe) and the thus ensuring high capacity connection to the rest of the Internet world. However, practice has shown that it can barely follow the needs of the growing number of members of Internet communities. When selecting an ISP of significance is the number of services that it provides to its customers. All services provided by e-mail, but do not provide any service to FTP, newsgroups, renting space on the disc, certain program support and etc. CARNet allows for almost all university departments.

User from their computers at work or at home by joining the Internet can:

Exchange electronic mail (e-mail) to any Internet user in any location on the planet.
Participate in off-line (indirectly, not in real time) discussions via e-mail with people with similar interests through 'mailing lists' and 'News Groups'.
Participate live (in real time) in a conversation with another person via the 'Internet video phone' (like Skype), or audio-video conferencing between multiple people using a specially designed computer programs and equipment.
Participate in on-line (directly, in real time) written discussion with a larger group of people who use the 'Internet Relay Chat' (IRC) service - chat rooms.
To work on a remote computer using the 'Telnet' service or some per function quite the same.
Take files of any type (download) from remote computers and deliver files (upload) them with an FTP (File Transfer Protocol) service.
Reading complex documents using 'hypertext'. Clicking on a keyword or image on the screen the user is automatically goes to other facilities within the same or other domains.
Read multimedia documents found on WWW (World Wide Web) that contain text, graphics, sound, and video using intelligent browser web presentation, as 'Google Chrome', 'Firefox' or 'Internet Explorer' program support.
Learning and practicing for the exam and achieve appropriate certification.
Search the Web, documents, various WWW sites or via dedicated international service, as 'Google' and 'Yahoo!', over subscribed keywords to find the desired documents.
Publicly disclose their images or pictures of his grandchildren, and who wants to can publish a picture of mother in law.
Advertise your business in a variety of ways, from setting up video clips to the creation of their own website.
Paying bills through the 'Internet Banking'.
Buy and spend money :-), advertise and offer for sale.
Read web editions of newspapers or say 'IT Alphabet'.
Play simple games and ..... who knows what else.

- See more at: http://www.informatics.buzdo.com/p914-internet-services.htm#sthash.uPOS9LOr.dpuf

History of the Internet

Origins of the Internet

The first recorded description of the social interactions that could be enabled through networking was a series of memos written by J.C.R. Licklider of MIT in August 1962 discussing his "Galactic Network" concept. He envisioned a globally interconnected set of computers through which everyone could quickly access data and programs from any site. In spirit, the concept was very much like the Internet of today. Licklider was the first head of the computer research program at DARPA,4 starting in October 1962. While at DARPA he convinced his successors at DARPA, Ivan Sutherland, Bob Taylor, and MIT researcher Lawrence G. Roberts, of the importance of this networking concept.

Leonard Kleinrock at MIT published the first paper on packet switching theory in July 1961 and the first book on the subject in 1964. Kleinrock convinced Roberts of the theoretical feasibility of communications using packets rather than circuits, which was a major step along the path towards computer networking. The other key step was to make the computers talk together. To explore this, in 1965 working with Thomas Merrill, Roberts connected the TX-2 computer in Mass. to the Q-32 in California with a low speed dial-up telephone line creating the first (however small) wide-area computer network ever built. The result of this experiment was the realization that the time-shared computers could work well together, running programs and retrieving data as necessary on the remote machine, but that the circuit switched telephone system was totally inadequate for the job. Kleinrock's conviction of the need for packet switching was confirmed.

In late 1966 Roberts went to DARPA to develop the computer network concept and quickly put together his plan for the "ARPANET", publishing it in 1967. At the conference where he presented the paper, there was also a paper on a packet network concept from the UK by Donald Davies and Roger Scantlebury of NPL. Scantlebury told Roberts about the NPL work as well as that of Paul Baran and others at RAND. The RAND group had written a paper on packet switching networks for secure voice in the military in 1964. It happened that the work at MIT (1961-1967), at RAND (1962-1965), and at NPL (1964-1967) had all proceeded in parallel without any of the researchers knowing about the other work. The word "packet" was adopted from the work at NPL and the proposed line speed to be used in the ARPANET design was upgraded from 2.4 kbps to 50 kbps.

In August 1968, after Roberts and the DARPA funded community had refined the overall structure and specifications for the ARPANET, an RFQ was released by DARPA for the development of one of the key components, the packet switches called Interface Message Processors (IMP's). The RFQ was won in December 1968 by a group headed by Frank Heart at Bolt Beranek and Newman (BBN). As the BBN team worked on the IMP's with Bob Kahn playing a major role in the overall ARPANET architectural design, the network topology and economics were designed and optimized by Roberts working with Howard Frank and his team at Network Analysis Corporation, and the network measurement system was prepared by Kleinrock's team at UCLA.

Due to Kleinrock's early development of packet switching theory and his focus on analysis, design and measurement, his Network Measurement Center at UCLA was selected to be the first node on the ARPANET. All this came together in September 1969 when BBN installed the first IMP at UCLA and the first host computer was connected. Doug Engelbart's project on "Augmentation of Human Intellect" (which included NLS, an early hypertext system) at Stanford Research Institute (SRI) provided a second node. SRI supported the Network Information Center, led by Elizabeth (Jake) Feinler and including functions such as maintaining tables of host name to address mapping as well as a directory of the RFC's.

One month later, when SRI was connected to the ARPANET, the first host-to-host message was sent from Kleinrock's laboratory to SRI. Two more nodes were added at UC Santa Barbara and University of Utah. These last two nodes incorporated application visualization projects, with Glen Culler and Burton Fried at UCSB investigating methods for display of mathematical functions using storage displays to deal with the problem of refresh over the net, and Robert Taylor and Ivan Sutherland at Utah investigating methods of 3-D representations over the net. Thus, by the end of 1969, four host computers were connected together into the initial ARPANET, and the budding Internet was off the ground. Even at this early stage, it should be noted that the networking research incorporated both work on the underlying network and work on how to utilize the network. This tradition continues to this day.

Computers were added quickly to the ARPANET during the following years, and work proceeded on completing a functionally complete Host-to-Host protocol and other network software. In December 1970 the Network Working Group (NWG) working under S. Crocker finished the initial ARPANET Host-to-Host protocol, called the Network Control Protocol (NCP). As the ARPANET sites completed implementing NCP during the period 1971-1972, the network users finally could begin to develop applications.

In October 1972, Kahn organized a large, very successful demonstration of the ARPANET at the International Computer Communication Conference (ICCC). This was the first public demonstration of this new network technology to the public. It was also in 1972 that the initial "hot" application, electronic mail, was introduced. In March Ray Tomlinson at BBN wrote the basic email message send and read software, motivated by the need of the ARPANET developers for an easy coordination mechanism. In July, Roberts expanded its utility by writing the first email utility program to list, selectively read, file, forward, and respond to messages. From there email took off as the largest network application for over a decade. This was a harbinger of the kind of activity we see on the World Wide Web today, namely, the enormous growth of all kinds of "people-to-people" traffic.

The Internet and Users

The Internet

The Internet is a global network connecting millions of computers. More than 190 countries are linked into exchanges of data, news and opinions.

Internet Users Worldwide

According to Internet Live Stats, as of August 07, 2015 there was an estimated 3,179,035,200 Internet users worldwide. The number of Internet users represents nearly 40 percent of the world's population. The largest number of Internet users by country is China, followed by the United States and India.

In September 2014, the total number of websites with a unique hostname online exceeded 1 billion. This is an increase from one website in 1991. The first billion Internet users worldwide was reached in 2005.