eScience Lectures Notes : Internet History and Principles

Slide 1 : 1/36 : From New Media to The Web (index.en.html)

COMP1710 H2>

Tools for New Media and the Web

--- or ---

Tools, Design and Management of

Maturing Hypermedia

From New Media to The Web

Click here to start or press 's'tart or 'i',

then 'n'ext or 'b'ack

Click here for the 't'able of Content

Slide 2 : ToC : Internet History and Principles (tableOfContent.en.html)

Table of Contents (36 slides) for the presentation :

Internet History and Principles

Slide 3 : 3/36 : New Media and Web (intro.en.html)

In this session : Internet : from the Mail to the Web

Special dedication to the EFF and its guide

EFF's (Extended) Guide to the Internet ...
(This is Version 2.3, published in September 1994)


Zen and the Art of the Internet
A Beginner's Guide to the Internet, First Edition, January 1992

Slide 4 : 4/36 : What to do on the (Inter)Net : From Mail (quoiFaire.en.html)

What to do on the (Inter)Net : From Mail


AlphaWorld in February 1998

"Satellite" maps of a growing city in AlphaWorld, a huge 3D multi-user virtual world run by ActiveWorlds. The maps were produced by Roland Vilett at different snap-shots over the past five years and by comparing them you can clearly see the rapid urban development in this particular corner of cyberspace.

Dialog, virtual meetings, one2one to many2many.

  • Email : Electronic Mail

  • chat, IRC, Instant Messaging

  • Mailing lists, newsgroups, usenet

  • Televirtuality : when your avatar represent you

Virtual communities, Networked Virtual Environment, or NVE

Slide 5 : 5/36 : What to do on the (Inter)Net : to the Web (quoiFaire2.en.html)

What to do on the (Inter)Net : to the Web

Work together

Remote connection

Download files, access information, Databases, surf the Web

Slide 6 : 6/36 : What to find on the Web ? (quoiTrouver.en.html)

What to find on the Web ?


Sharwares, Freewares, Postcardware

Technical Specification

Information from the government

Institutes, Organisations (NGO), companies' presentations

Books, Music, Art



Product catalogs, Shops

Lots of Advertising

What you find has been put there by somebody. It could be you.


Slide 7 : 7/36 : Internet History (historique.en.html)

Internet History

1957 : US forms the Advanced Research Projects Agency (ARPA)

In response to the launch of  USSR's Sputnik

60s : Start of research

69 : ARPANET commissioned by DoD for research into networking


Slide 8 : 8/36 : Internet History : 70s : Development (historique70.en.html)

Internet History : 70s : Development

70s : ARPANET is born.

73 : Internationalisation : England via Norway


Slide 9 : 9/36 : Internet History : 80s : Universities (historique80.en.html)

Internet History : 80s : Universities

80s : Adoption of TCP/IP (82).

early 1980s, a permanent Australian email connection to the U.S. ARPAnet

81 : Minitel (Teletel) is deployed across France by France Telecom

82 : DCA and ARPA : Transmission Control Protocol (TCP) and Internet Protocol (IP)


Slide 10 : 10/36 : Internet History (historique90.en.html)

Internet History : 90s : Web Boom

90s : Internet Boom

French Web site map (UREC)

January 94


July 94


March 95


September 95


January 96


May 96


16th december 96


2nd october 97

end of the service

Slide 11 : 11/36 : Internet History : Sources (historiqueOthers.en.html)

Internet History : Sources

Origins and Nature of the Internet in Australia
Roger Clarke

History of Internet and WWW: The Roads and Crossroads of Internet  History
by Gregory R. Gromov

Hobbes' Internet Timeline

Yahoo Computer and Internet


Slide 12 : 12/36 : Evolution of the Net (evolution.en.html)

Evolution of the Net

Slide 13 : 13/36 : Evolution of the Net (2) (evolution2.en.html)

Evolution of the Net (2) and

Slide 14 : 14/36 : Evolution of the Net (3) (evolution3.en.html)

Evolution of the Net (3)

Slide 15 : 15/36 : In France since ... The Minitel (minitel.en.html)

In France since 1982 The Minitel

Source :

Minitel screen
Source :

In Every home

Efficient business model ...

... even if really bad for the customer

1985 : yellow/whites pages

the web ... 10 years later

1995 : new model with card reader integrated ...



Slide 16 : 16/36 : Evolution of the Net (3b) (evolution3b.en.html)

Evolution of the Net (3b)

Slide 17 : 17/36 : Evolution of the Net (4) (evolution4.en.html)

Evolution of the Net (4)

Slide 18 : 18/36 : Evolution of the Net (5) (evolution5.en.html)

Evolution of the Net (5)

Slide 19 : 19/36 : Evolution of the Net (6) : But ! (evolution6.en.html)

Evolution of the Net (6) : But !

Internet Users as a Percentage of Population, mid-2002

Region and Country User Count (millions) Population (millions) Users (%)
Middle East / West Asia
* Hong Kong
* South Korea
* Australia
* Singapore
* Japan
* India
* remainder
The Americas
* Canada
* Latin America
* Iceland
* Sweden
* Denmark
* The Netherlands
* Norway
* United Kingdom
* Finland
* Russia
* remainder

Slide 20 : 20/36 : Evolution of the Net (6b) : But ! (evolution6b.en.html)

Evolution of the Net (6b) : But !

Thursday, 15 July 2004, In India : Internet connectivity is 0.4 per cent

Tuesday, 1 March 2005, India: Knowledge Superpower

And in Africa the abailable bandwith is quite low
international bandwidth in bits per capita (BPC) available in Mid 2002

Bits per Capita in Africa

Internet connectivity is 0.4 per cent

Thursday, 15 July , 2004, 14:38
Internet and broadband base in the country is still languishing at 0.4 per cent and 0.02 per cent, minister of state for communications and information technology Shakeel Ahmad said today. The government is examining recommendations of the Telecom Regulatory Authority of India (TRAI) to accelerate growth of Internet and broadband penetration, he told the Rajya Sabha in a written reply.

Low Bits per capita in Africa

Bits per capita is a relatively new measure of Internet use. The size of the Internet in a country indicates an element of its progress towards an information-based economy. International Internet bandwidth provides a measure of Internet activity because many people share accounts, or use corporate and academic networks along with cyber cafes and business centers. Outgoing bandwidth also takes better account of the wide range of possible use, from those who write a few emails each week, to users who spend many hours a day on the net browsing, transacting, streaming, and downloading. Because of this, the often used 'Number of Internet Users' indicator may have less relevance in the developing world than in other places.
The coloured circle in each country on the map shows, to exact scale, the international bandwidth in bits per capita (BPC) available in Mid 2002 from publicly accessible IP networks.
Bandwidth availability in Africa varies tremendously, but is generally very low compared to developed countries. Although there are few intra-African links, the marine fibre cables shown are now all operational and should provide faster and cheaper routes within and out of Africa.

Slide 21 : 21/36 : Evolution of the Net (7) (evolution7.en.html)

Evolution of the Net (7) : even in Australia

In the first quarter of 2003, it was estimated that 75% of Australians 16 years and over had access to the Internet.
Sweden (90%), U.S.A. (86%), France (55%)

Online time per user per month averaged 10 hours over 18 sessions.

Broadband penetration continues to be low

86% of connections still by modem

Cable available only in affluent suburbs in Sydney and Melbourne, plus a proportion of Canberra

ADSL is only feasible within 3-4 km of a proportion of telephone exchanges

In many areas, far less than 56Kbps from dial-up connections

Government (June 2003) : 19.2Kbps = acceptable target minimum transmission speed

Broadband penetration, because of high pricing and incomplete availability, continues to be low, with 86% of connections still by modem (but including a few ISDN users). Cable is available only in affluent suburbs in Sydney and Melbourne, plus a proportion of Canberra, and ADSL is only feasible within 3-4 km of a proportion of telephone exchanges. SDSL is only now becoming available. Satellite is even more expensive than the other broadband alternatives. See also Sale (2001).

Moreover, users in many areas where broadband is unavailable or excessively expensive get far less than 56Kbps from their dial-up connections. The Government has been successful in its endeavours to avoid survey information about achieved dial-up speeds becoming publicly available. As late as June 2003, in its response to the Regional Telecommunications (Estens) Inquiry, it made clear that it still regards 19.2Kbps as being acceptable as a target minimum transmission speed for regional and rural Australia, and even for less fortunate urban areas.


Slide 22 : 22/36 : What is the Internet ? (reseauSimple.en.html)

What is Internet ?

An Infrastructure (electricity grid, water reticulation pipework) designed to transfer digital data between computers

The Internet is an infrastructure, in the sense in which that term is used to refer to the electricity grid, water reticulation pipework, and the networks of track, macadam and re-fuelling facilities that support rail and road transport. Rather than energy, water, cargo or passengers, the payload carried by the information infrastructure is messages.

The term 'Internet' has come to be used in a variety of ways. Many authors are careless in their usage of the term, and considerable confusion can arise. Firstly, from the perspective of the people who use it, the Internet is a vague, mostly unseen, collection of resources that enable communications between one's own device and devices elsewhere. Exhibit 3.2 provides a graphical depiction of that interpretation of the term 'Internet'.


Slide 23 : 23/36 : internet or Internet (reseauComplet.en.html)

internet or Internet

'internet' (with a lower-case 'i') : any set of networks interconnected using the Internet Protocol Suite (TCP/IP)

The Internet (with an upper-case 'I'), or sometimes 'the open, public Internet' : the largest set of networks interconnected using the Internet Protocol Suite.

Intranet, Extranet


From a technical perspective, the term Internet refers to a particular collection of computer networks which are inter-connected by means of a particular set of protocols usefully called 'the Internet Protocol Suite', but which is frequently referred to using the names of the two central protocols, 'TCP/IP'.

The term 'internet' (with a lower-case 'i') refers to any set of networks interconnected using the Internet Protocol Suite. Many networks exist within companies, and indeed within people's homes, which are internets, and which may or may not have a connection with any other network. The Internet (with an upper-case 'I'), or sometimes 'the open, public Internet', is used to refer to the largest set of networks interconnected using the Internet Protocol Suite.

Additional terms that are in common use are Intranet, which is correctly used to refer to a set of networks that are internal to a single organisation, and that are interconnected using the Internet Protocol Suite (although it is sometimes used more loosely, to refer to an organisation's internal networks, irrespective of the protocols used). An Extranet is a set of networks within a group of partnered organisations, that are interconnected using the Internet Protocol Suite.


Slide 24 : 24/36 : Really complex network (reallyComplex.en.html)

Really complex network

A network comprises nodes (computers) and arcs (means whereby messages can be transmitted between the nodes)

fragility is compensated by redundancy

multiply-connected topology allow eventual robustness and resilience



A network comprises nodes (computers) and arcs (means whereby messages can be transmitted between the nodes). A network suffers from fragility if individual nodes are dependent on only a very few arcs or a very few other nodes. Networks are more reliable if they involve a large amount of redundancy, that is to say that they comprise many computers performing similar functions, connected by many different paths. The Internet features multiple connections among many nodes. Hence, when (not if) individual elements fail, the Internet's multiply-connected topology has the characteristics of robustness (the ability to continue to function despite adverse events), and resilience (the ability to be recovered quickly and cleanly after failure). The Internet also has the characteristic of scalability, that is to say that it supports the addition of nodes and arcs without interruptions, and thereby can expand rapidly without the serious growing pains that many other topologies and technologies suffer.

The conception of the Internet protocols took place during the 1960s and 1970s, at the height of the Cold War era. Military strategists were concerned about the potentially devastating impact of neutron bomb explosions on electronic componentry, and consequently placed great stress on robustness and resilience (or, to use terms of that period, 'survivability' and 'fail-soft'). These characteristics were not formal requirements of the Internet, and the frequently-repeated claims that 'the Internet was designed to withstand a neutron bomb' are not accurate. On the other hand, those design characteristics were in the designers' minds at the time.


Slide 25 : 25/36 : Packet Switching (packetSwitching.en.html)

Packet Switching

Phone network : provide a dedicated, switched path to the caller and the receiver for the duration of the call

internets : Messages are divided into relatively small blocks of data, commonly referred to as packets.

Routing : a way to send each packet at the right address



The networks that had been designed to support voice-conversations provided a dedicated, switched path to the caller and the callee for the duration of the call, and then released all of the segments for use by other callers. Data networks were designed to apply a very different principle. Messages were divided into relatively small blocks of data, commonly referred to as packets. Packets despatched by many senders were then interleaved, enabling efficient use of a single infrastructure by many people at the same time. This is referred to as a packet-switched network, in comparison with the telephony PSTN, which is a circuit-switched network. The functioning of a packet-switched network can be explained using the metaphor of a postal system (Clarke 1998).


Slide 26 : 26/36 : Layers of Internet Protocols (layers.en.html)

Layers of Internet Protocols

Protocol : A set of rules, A Language

Layers : adaptation to different technology / solution






Delivery of data to an application


HTTP (the Web), SMTP (email despatch)


Delivery of data to a node




Data addressing and transmission




Network access


Ethernet, PPP


Handle Signals on a Medium



co-axial cable, Phone (twisted-pair copper cable), fibre-optic cable, Air

TCP: Transmission Control Protocol.

IP: Internet protocol.

Functionality: For efficient data communication, data is split into small units (packets) and each packet is sent through an appropriate path. TCP keeps track of individual units, and IP takes care of handling the actual delivery of data units.

NB : OSI model: 7 layers (ISO standard).

For devices to communicate successfully over a packet-switched network, it is necessary for them to work to the same rules. A set of rules of this kind is called a protocol. Rather than a single protocol, the workings of packet-switched networks, including the Internet, were conceived as a hierarchy of layers. This has the advantage that different solutions can be substituted for one another at each layer. For example, the underlying transmission medium can be twisted-pair copper cable (which exists in vast quantities because that was the dominant form of wiring for voice services for a century), co-axial cable (which is used for cable-TV and for Ethernet), fibre-optic cable, or a wireless medium using some part of the electromagnetic spectrum. This layering provides enormous flexibility, which has underpinned the rapid changes that have occurred in Internet services.

The deepest layers enable sending devices to divide large messages into smaller packets, and generate signals on the transmission medium that represent the content of the packets; and enable receiving devices to interpret those signals in order to retrieve the contents, and to re-assemble the original message. The mid-layer protocols provide a means of getting the messages to the right place, and the upper-layer protocols use the contents of the messages in order to deliver services. Exhibit 3.3 provides an overview of the layers as they are currently perceived.


Slide 27 : 27/36 : Internet Application Protocols and Services (protocoles.en.html)

Internet Application Protocols and Services


A Taxonomy of Internet Services

The application protocol layer utilises the transmission medium and the lower and middle protocol layers as an infrastructure, in order to deliver services. Some services are provided by computers for other computers, some by computers but for people, and some by people and for people. Key services that are available over the underlying infrastructure include e-mail and the World Wide Web (which together dominate Internet traffic volumes), file transfer and news (also referred to as 'netnews' and by its original name 'Usenet news'). There are, however, several score other services, some of which have great significance to particular kinds of users, or as enablers of better-known services.

During the early years, the services that were available were primarily remote login to distant machines (using rlogin and telnet from 1972), email (from 1972), and file transfer protocol (ftp, from 1973). In 1973, email represented 75% of all ARPANET traffic. By 1975, mailing lists were supported, and by 1979-82 emoticons such as (:-)} were becoming established. By 1980, MUDs and bulletin boards existed. The email service in use in 2004 was standardised as early as 1982. Synchronous multi-person conversations were supported from 1988 by Internet Relay Chat. This was also significant because the innovation was developed in Finland, whereas a very large proportion of the technology had been, and continues to be, developed within the U.S.A.

By 1990, over 100,000 hosts were connected, and innovation in application-layer protocols, and hence in services, accelerated. Between 1990 and 1994, a succession of content-provision, content-discovery and content-access services were released, as existing news and bulletin-board arrangements were reticulated over the Internet, and then enhanced protocols were developed, including archie (an indexing tool for ftp sites developed in Canada), the various 'gopher' systems (generic menu-driven systems for accessing files, supported by the veronica discovery tool), and Brewster Kahle's WAIS content search engines. Between 1991 and 1994, the World Wide Web emerged, from an Englishman and a Frenchman working in Switzerland; and in due course the Web swamped all of the other content-publishing services. By 1995, it was already carrying the largest traffic-volume of any application-layer protocol.

Exhibit 3.4, which is a revised version of an exhibit in Clarke (1994c), provides a classification scheme for the services available over the Internet.


Slide 28 : 28/36 : What is Internet ? (reseauSimple2.en.html)

But it is so simple

One computer, one IP, one address



Slide 29 : 29/36 : IP Number (numIP.en.html)

IP Number

The address of any machine connected to an internet network

Coded on 4 bytes

255x255x255x255 = 4,2.109 possible computers connected to the Internet

E.g.. :, ..., ...

Distributed by your ISP, who got it from the ICANN (Internet Corporation for Assigned Names and Numbers)

The Internet Corporation for Assigned Names and Numbers (ICANN) is an internationally organized, non-profit corporation that has responsibility for Internet Protocol (IP) address space allocation, protocol identifier assignment, generic (gTLD) and country code (ccTLD) Top-Level Domain name system management, and root server system management functions. These services were originally performed under U.S. Government contract by the Internet Assigned Numbers Authority (IANA) and other entities. ICANN now performs the IANA function.
As a private-public partnership, ICANN is dedicated to preserving the operational stability of the Internet; to promoting competition; to achieving broad representation of global Internet communities; and to developing policy appropriate to its mission through bottom-up, consensus-based processes.

Different  class, for different type of subnet

Addresses 0 and 1 have special meaning. Roughly 0 means itself, 1 means all.


No. of Networks can be served

No. of hosts each network can have



27 -2 = 126

224 -2 = 16777214

Really big organisations


214 -2 = 16382

216 -2 = 65534

Big Companies, Universities (ANU : 2 class B)


221 -2 = 2097150

28 -2 = 254

School small organizations


228 -2 = 268435454

multicast addresses



227 -2 = 134217726

reserved addresses


Obviously not enough ! (6,500,415,220 projected to 02/28/06 at 01:09 GMT (EST+5))

IP masquerading behind proxy/firewall

IPng, IPv6 increases the IP address size from 32 bits to 128 bits

Why :-)

Countries Ranked by Population: 2006
Rank Country Population
1 China 1,313,973,713 : Annual rate of growth (percent)................ 0.6 / Total fertility rate (per woman)............... 1.7
2 India 1,095,351,995 : Annual rate of growth (percent)................ 1.4 / Total fertility rate (per woman)............... 2.8
3 United States 298,444,215
4 Indonesia 245,452,739
5 Brazil 188,078,227

Source : and

Slide 30 : 30/36 : Domain Name System/Service (DNS) (dns.en.html)

Domain Name System/Service (DNS)

How can people remember the tedious IP addresses?

It is easier to remember than, isn't it?

cs, anu, edu, and au are all domain names.

There are many other domain names.

DNS keeps a mapping from domain names to IP addresses and the reverse.

Domain names can be composite.

E.g.,, are all valid domain names.

IP number / Postal Code  //  Domain Name / Town Name

pingu, www, cs


com, edu, org

au, uk

Name or alias of a machine, or department

Entity (university,

Top Level Name


pingu, www


ina, google

fr, com

Name or alias of the machine



Country or Top Level Name


ina, google

fr, com

Name or alias of the machine


Country or Top Level Name

Slide 31 : 31/36 : Domain Name System/Service (DNS) (dns2.en.html)

Domain Name System/Service (DNS) (2)

Guess where the information come from

2 letters : by country

























3 or more letters : Top Level Name by type

Often used as a second level after the country domain


Usually a company or other commercial institution or organization


An educational institution (eg ANU)


United States Government


Internationale Organisation (Otan)


United States Military


Network related activities


intended to serve the noncommercial community, NGO (Unesco)

These un-sponsored top-level domains are open and unrestricted. Traditionally, however, most names are intended or reserved for specific use, as listed below. Please contact your registrar for more information or visit the Registry websites listed below.

The .aero, .coop, and .museum TLDs are sponsored TLDs and are designed for use within a specified community. Registration restrictions for these TLDs have been developed by the sponsor with input from the community.

Source :

Slide 32 : 32/36 : Domain Name System/Service (DNS) (dns3.en.html)

Domain Name System/Service (DNS) (3)

Domain Name attributed by a Registrar or you local SysAdm

Domain names can be registered through many different companies (known as "registrars") that compete with one another.
The registrar you choose will ask you to provide various contact and technical information that makes up the registration. The registrar will then keep records of the contact information and submit the technical information to a central directory known as the "registry." This registry provides other computers on the Internet the information necessary to send you e-mail or to find your web site. You will also be required to enter a registration contract with the registrar, which sets forth the terms under which your registration is accepted and will be maintained.

Public information provided from Internic and local instance of Internic (the DNS)

Conversion between Name and IP number : Dig / NSlookup

Who that name belongs to : WhoIs or WhoIs

Each DNS server ensures that no two domains under it have the same domain name. Then as a result, no two domain names worldwide are the same.

No one can practically handle the job of mapping domain names to the corresponding IP addresses worldwide.

Domain names keep changing, and there are many new added ones.

DNS is a hierarchically structured, distributed database system.

When an IP address is to be found given a domain name, a library procedure called resolver requests DNS server for the IP address. If found, it is returned to the caller. Otherwise the DNS server calls up a higher level DNS. Higher level DNS may call some other higher or lower level DNS servers.

ICANN is at the root of the Internet

Internet Corporation for Assigned Names and Numbers

ICANN still belongs to the US : Big political issue : should be associated to the UN !

Eg. ICANN gave away the'.com' to the US registrare VeriSign up to 2012: 6$/year   (+7% raise a year) * 35 billion name ...

Slide 33 : 33/36 : The WWW, ...    The World Wide Web, ...    The Web (web.en.html)

The WWW, ...    The World Wide Web, ...    The Web


Web = HTTP + URL + HTML (*)


HTTP : HyperText Transfer Protocol : Transfer of Data

Other protocols are available

Today browsers are meta browsers able to understand various protocol

From HTTP1.0 to HTTP1.1



URL : Address of data

HTML : Format of text to create Hypermedia pages/documents

(*) + Browser + Server

Slide 34 : 34/36 : IP Number (URL.en.html)


URL: Uniform Resource Locator

Address of resources worldwide is identified by its URL.

Everything you need to know to access a specific ressource



or more simply :  protocol://machineName/accessPath

Some examples

For FPT:

For Gopher:   gopher://

For File:   file:///Users/Sites_Docs/

For Mail:

For Skype: callto://toto



Slide 35 : 35/36 : URL: Uniform Resource Locator (URL2.en.html)

URIs, URLs, and URNs

URL: How to access a ressource to a specific location

URN : Uniform Resource Name

How to specify a ressouce in a unique way, but without restricting its access to a specific location ( urn:isbn:n-nn-nnnnnn-n )

URI : Uniform Resource Identifier = URL + URN + ???

Generic term to name all the standardised ways to design an internet ressource

1 URI Partitioning
There is some confusion in the web community over the partitioning of URI space, specifically, the relationship among the concepts of URL, URN, and URI. The confusion owes to the incompatibility between two different views of URI partitioning, which we call the "classical" and "contemporary" views.
1.1 Classical View
During the early years of discussion of web identifiers (early to mid 90s), people assumed that an identifer type would be cast into one of two (or possibly more) classes. An identifier might specify the location of a resource (a URL) or its name (a URN) independent of location. Thus a URI was either a URL or a URN. There was discussion about generalizing this by addition of a discrete number of additional classes; for example, a URI might point to metadata rather than the resource itself, in which case the URI would be a URC (citation). URI space was thus viewed as partitioned into subspaces: URL and URN, and additional subspaces, to be defined. The only such additional space ever proposed was URC and there never was any buy-in; so without loss of generality it's reasonable to say that URI space was thought to be partitioned into two classes: URL and URN. Thus for example, "http:" was a URL scheme, and "isbn:" would (someday) be a URN scheme. Any new scheme would be cast into one or the other of these two classes.
1.2 Contemporary View
Over time, the importance of this additional level of hierarchy seemed to lessen; the view became that an individual scheme does not need to be cast into one of a discrete set of URI types such as "URL", "URN", "URC", etc. Web-identifer schemes are in general URI schemes; a given URI scheme may define subspaces. Thus "http:" is a URI scheme. "urn:" is also a URI scheme; it defines subspaces, called "namespaces". For example, the set of URNs of the form "urn:isbn:n-nn-nnnnnn-n" is a URN namespace. ("isbn" is an URN namespace identifier. It is not a "URN scheme" nor a "URI scheme").
Further according to the contemporary view, the term "URL" does not refer to a formal partition of URI space; rather, URL is a useful but informal concept: a URL is a type of URI that identifies a resource via a representation of its primary access mechanism (e.g., its network "location"), rather than by some other attributes it may have. Thus as we noted, "http:" is a URI scheme. An http URI is a URL. The phrase "URL scheme" is now used infrequently, usually to refer to some subclass of URI schemes which exclude URNs.
1.3 Confusion
The body of documents (RFCs, etc) covering URI architecture, syntax, registration, etc., spans both the classical and contemporary periods. People who are well-versed in URI matters tend to use "URL" and "URI" in ways that seem to be interchangable. Among these experts, this isn't a problem. But among the Internet community at large, it is. People are not convinced that URI and URL mean the same thing, in documents where they (apparently) do. When one sees an RFC that talks about URI schemes (e.g. [RFC 2396]), another that talks about URL schemes (e.g. [RFC 2717]), and yet another that talks of URN schemes ([RFC 2276]) it is natural to wonder what's the difference, and how they relate to one another. While RFC 2396 1.2 attempts to address the distinction between URIs, URLs and URNs, it has not been successful in clearing up the confusion.

URI : a way to fight against broken links ?

Cool URIs don't change, by Tim Berners-Lee

What makes a cool URI?
A cool URI is one which does not change.
What sorts of URI change?
URIs don't change: people change them.

Why should I care?

When you change a URI on your server, you can never completely tell who will have links to the old URI. They might have made links from regular web pages. They might have bookmarked your page. They might have scrawled the URI in the margin of a letter to a friend.
When someone follows a link and it breaks, they generally lose confidence in the owner of the server. They also are frustrated - emotionally and practically from accomplishing their goal.
Enough people complain all the time about dangling links that I hope the damage is obvious. I hope it also obvious that the reputation damage is to the maintainer of the server whose document vanished.

Slide 36 : 36/36 : URL : default values (URL3.en.html)

URL : default values

From    escience/nm   

used in a web browser   http://escience:80/nm

within a specified network ( ANU, is the ISP)

Server : no suffix ? it must be a directory :

Server : is there a file named index.html  in that directory ? yes ? Let's return that one :

And an additional step, not usual

Browser : Oh ? That file asks me to load another one instead ? let's do it :


NB : About directory and file naming, lots of things are possible, but if you don't want to bother remembering more:


The general form of an URL has four parts

  1. A scheme followed by a colon.
  2. A server name.
  3. An optional port number. Standard or default port numbers are:
  4. A path.

    * Ftp uses port 20 for data and port 21 for flow control.

Source :