Wireless Web (4W)
...how to free the WWW from wires (and not just wires)
Marco Zennaro, [email protected]
Carlo Fonda, [email protected]
RadioCommunications Unit of
the ICTP-ARPL (Trieste, Italy)
Science & Technology Collaborium
http://www.collaborium.org
Workshop on Web Enabling
Technologies & Strategies
for Scientific e-Learning
14-23 April 2004 Trieste, Italy
Agenda
3 steps to f r e e t h e w w w
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1: from the wires of
network cables
2: from the “wires” of
network configuration
3: from the “wires” of
browser/platform
4, 5, 6... ???
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Look mom, no wires!
802.11a/b/g
20 minutes for an introductory
talk about wireless networking
and its interaction with the Web:
Web needs the network (☑)
Why to go wireless ?
Is wireless networking for
everybody ? I think it is☻!
Network structure
- the theory Any generic “network” is a complex structure,
made of many parts:
clients (customers)
servers (service providers)
network media (communication ways)
network devices (traffic control system)
protocols (traffic rules)
contents (information carried over the net)
Network structure
- an example Let’s think to the road system. We can identify
the following parts:
clients (customers) people’s houses
servers useful places people want to reach
network media roads and highways system
network devices policemen, traffic signs
protocols the traffic laws
contents people or goods that are moved
Network structure
–Internet networking–
Now we can look at the real Internet. These
are the components parts:
clients (customers) people’s computers
servers webservers, on-line databases
network media fibers, cables, wireless
network devices routers, switches, hubs
protocols TCP/IP, HTTP and many others
contents webpages, files, data, ... (bits)
So, what wireless means?
network media:
wireless no cables no roads!
no geographical constraints
you don’t drive a car, you now fly on a jetplane
you solve many old problems, but you may also
have to face few new problems...
Today’s first lesson:
going wireless is
like flying on air
instead of
travelling on roads
But...
Why (or when) do we
*really* need
to go wireless?
Wired vs Wireless
Local Area Networking
Most of the time, users do not experience a
difference between using a wireless network
and using a wired network.
To plan, design and install a wireless network is
quite different:
distance and line-of-sight
networks co-location, interferences
radiopropagation and environment
mobility, fast deployment and re-location
Distance and Line-of-sight
7 Km
The cost of a wireless
network increases
with the distance (and
with the bandwidth),
the relation is usually
more-than-linear.
Wireless networks
usually connect one
or more locations that
you can visibly see.
Co-location and interferences
Co-location of more
networks usually affects
the performances.
Spectrum management
(frequencies and usage
coordination) is required
at international level
(ITU).
Interferences may occur
from other e.m. sources.
Radiopropagation and environment
Performances of wireless
networks may be affected
by the properties of the
atmosphere (troposphere,
ionosphere), of the terrain,
of surrounding structures.
Worst case scenarios (i.e.
bad weather days) must
be considered.
Wireless network design
requires both technical
and scientific knowledge.
Mobility
Wireless networks can
connect mobile users.
The fixed network
infrastructure is today:
what telephony has been for the past 50
years,
a primary communication service;
what a good library structure has been for
the past 500 years,
a primary knowledge source;
what an efficient road system has been for
the past 5000 years,
a primary escape way from
insulation:
Mobility is the next
step forward! (Now to
5 years, eventually ?)
Fast deployment and re-location
Wireless networks can
be deployed in a very
short time, i.e. for:
disaster recovery networks
rapid changes of
communication needs
Wireless equipment
can be recycled and
re-located in a short
time, upon the need,
saving time and
previous investments.
doc.: IEEE
96
March 19
Today’s second lesson:
going wireless, we
may face new
problems, some new
skills are required !
P802.11-9
6/49
March 96
802.11 Tu
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fixed or mobile ?
Mobile Wireless Access:
mobile phones (ETACS, GSM)
mobile data (1G, 2G, 3G, ...)
Fixed Wireless Access:
last mile problem
leapfrog poor or expensive
telecom infrastructures
voice/data integration
fixed or mobile ?
For the purpose of pure networking,
technologies for DIGITAL
fixed MOBILE
wireless
accessAND
SUBSCRIBERS
INTERNET USERS (WORLDWIDE)
are ideal for developing countries:
1000
PnP easy
PTT-free
800
USERS (Millions)
it’s cheap
600
400
200
0
1992
For Web ?
1993
1994
1995
1996
1997
1998
1999
2000
2001
YEAR
Mobile Telephone Subscribers
Internet Users
Source: ITU World Telecommunication Indicators Database.
33
IEEE STANDARDS VIEW OF WIRELESS
NETWORK TECHNOLOGIES
WWAN
<15 km
802.20 (proposed)
MAN
WiMAX
New standard for
Fixed broadband
Wireless. Trying to do
for MAN what Wi-Fi
did for LAN.
Wi-Fi®
Includes 802.11a/b/g.
<5 km
70 Mbit/s
802.16a/e
WLAN
<100 m
11-54 Mbit/s
802.11a/b, e, g
PAN
<10 m
~1 Mbit/s
802.15.1 (Bluetooth)
802.15.3 (UWB) *
802.15.4 (ZigBee)**
Source: International Telecommunications Union, “Birth of Broadband”, September 2003
* UWB: 100 Mbit/s
** ZigBee: 250 kbps
38
fixed wireless technologies
WLANs & WMANs
wireless networks were designed
(in 90es) for the LAN (indoor)
market, but in developing
countries there are even much
more useful outdoor, as MANs
(or even WANs), for distances
up to 10 Km (or 50 Km, WiMAX)
cost of wireless
the enormous success of this
technology has led to a dramatic
price reduction for the radio
devices:
>1000 US$ in 1992
<100 US$ in 2004
speed of wireless
the available data transfer rate
on the same radio channel
(bandwidth of 20 MHz) has
increased from 1 Mbps to 54
Mbps (even 74 Mbps for some
applications)
wireless standards
wireless networking has grown
incredibly fast thanks to a wide
adoption of common standards:
802.11, 802.11a/b/g protocols
WiFi ™ certification
brand/model
intercompatibility
wireless LANs
indoor/outdoor network
distribution among many clients
typical distance: 10 - 100 m
Point-to-MultiPoint structure:
master station (access point, AP)
client station (PCI card, PC card,
USB device, wireless bridge)
wireless MANs
used by ISPs (Point-toMultiPoint)
typical distances: 1-5
Km
may have a large
number of clients
coexistence problems
(no more than 3 nonoverlapping channels)
line–of–sight, security
issues, automatic and
remote management
wireless MANs
for private institutions or
companies:
Point-to-Multipoint
Point-to-Point (to larger
distance, less problems
of coexistence)
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planning and design of
the radiolinks
P2MP MANs
Point-to-Multipoint
Star topology, one AP, many stations
Omnidirectional antenna for AP
Directive antennas for stations
AP
STA
STA
STA
P2MP MANs
(cont.)
coexistence problem:
APs use omni antennas, so they may
interfere with other APs or stations
different channels can be used, but only
3 channels are non-overlapping
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coordination is required among APs
P2P MANs (WANs)
wireless long distance links (<10 Km)
provide connectivity to remote sites
broadband (1, 2, 5, 11, 54 Mbps)
no monthly/traffic fee, no recurrent
costs (unlike leased lines from PPT)
require skills for planning and
installation (power budget)
Power Budget
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The trasmitted power
decreases along its
way to the receiver:
Pt = trasmitted power
Pr = received power
Tx = Transmitter
Rx = Receiver
At, Gt = Attenuation
of cables and Gain
of the antenna at
the transmitter side
Ar, Gr = same for
the receiver side.
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Cheap radiolinks?
It is possible to build cheap
long–distance radiolinks, with
old PCs, Linux OS, off–the–shelf
WiFi devices (sold for indoor),
home–made antennas:
200-500 US$ per links
skill is required, but you can
find plenty of information and
tutorials, just surfing the Web
Antenna making
How to learn more?
http://wireless.ictp.trieste.it
Yearly ICTP-ARPL School on
Wireless Networking
(usually in February)
Radio Handbooks:
on Antenna Building
on WLAN setup
(ready for February 2005)
doc.: IEEE
Today’s third lesson:
fixed wireless may
be a good solution
for networking in
developing countries
96
March 19
P802.11-9
6/49
March 96
802.11 Tu
torial
Medium
s
Variation
an
parts from
is contains
reserved. Th
E, All rights
©1996 IEE
Copyright
t to change
draft, subjec
unapproved
3
March 96
802.11 Tu
torial
Uniq
f W irele
ueness o
nued)
ss (conti
y
• Mobilit
liability
ement
n in link re
er manag
– variatio
uires pow
q
re
e:
g
usa
ns
– battery
connectio
eamless”
– want “s
• Security
daries
ical boun
– no phys
s
N
A
L
g
pin
– overlap
change
ft, subject to
approved dra
from an un
tains parts
ed. This con
erv
res
hts
E, All rig
©1996 IEE
Copyright
2
Submission
*
4
, Sy
Greg Ennis
Mobile wireless
Mobile access
wireless:
cellphones
WAP
HTML, etc.
JAVA
etc...
Mobile wireless
Mobile access
wireless:
PDAs
PalmOS
Windows
(CE or Mobile)
Linux
other OSs
Mobile Browsing
Now, it’s just an
“added value” for
mobile devices that
are intended for
other purposes.
In a short time it
may become a key
feature and more
people will start to
browse wireless.
i.e. : http://www.cellmania.com
Test with Opera
Is your website mobile-ready ?
The best way to test web pages is
to use the devices themselves. This
may not always be practicable, but
the desktop versions of Opera 7 all
have built-in testing functionality.
http://my.opera.com/community/dev/device/writing/
http://my.opera.com/community/dev/device/testing/
The end of wired networking !?!
Ok, maybe not ;)
But now, after our
discussion about
wired VS wireless...
...do you have your
answer on what is
better for you ???
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Is the Web plug-n-play?!?
ZeroConf
10 minutes for a brief overview of
the most promising technology
for bringing network services to
non-technical people (or just lazy,
like me ;)
TCP/IP and web configuration
isn’t hard, is it ? You decide.
The only “easy configuration”
is zero configuration !
TCP/IP configuration
Static (nightmare):
configure IP address, netmask,
bradcast address, gateway
address, DNS address(es)
Dynamic (painless):
DHCP (eventually BootP)
Looking for services
Ok, the network is configured.
Now, where are the services ???
webservers, proxy, other
servers and clients (printing,
filesharing, chat and IM, etc...)
ZeroConf does all
Zero Configuration IP Networking:
Allocates addresses without a DHCP server.
Translates between names and IP addresses
without a DNS server.
Finds services, like printers, without a directory
server.
It’s an open standard of Internet Engineering
Task Force (IETF).
An example: Apple
Rendevouz is the Apple implementation of ZeroConf (IETF
standard) that enables automatic discovery of computers,
devices, and services on IP networks, allowing devices to
automatically find each other without the need to enter IP
addresses or configure DNS servers.
Safari, Apple’s web browser, uses Rendezvous to find any
web addresses on your local network. With the help of
Rendezvous, iChatAV lets you see which people are available
for chatting or video conferencing on your local network.
iTunes and iPhoto also use Rendezvous to facilitate sharing
music and photos on local networks. Printer manufacturers
Epson, HP, Lexmark, Canon, Xerox and Brother are
integrating Rendezvous into new printers to enable them to be
added and removed from networks without configuration.
When you add your Mac to a network, MacOSX will then
automatically discover and connect to the available
Rendezvous-enabled printers and you’re ready to print.
A new market...
It is important to understand that the
The
growth
of image based communications
mage
based
communications
Tutti i dirirtti riservati
Tutti i dirirtti riservati
purpose of zeroconf is not solely to
make current personal computer
networking easier to use, though
this is certainly a useful benefit. The
long-term goal of zeroconf is to
enable the creation of entirely new
kinds of networked products,
products that today would simply
not be commercially viable because
The growth of image based communications
of the inconvenience and support
costs involved in setting up,
configuring, and maintaining a
network to allow them to operate.
Incontro con TIM
Roma, 28 nov. 2k3
Roma, 28 nov. 2k3
8
8
mod_zeroconf
This module allows any Apache 2.0 web
server to register its services on a Zero
Configuration network. It is an open-source
project licensed under the Apache license.
http://www.spack.org/wiki/ZeroConf
T
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Web design for all !
XHTML + CSS
15 minutes for a brief story of
www and some suggestion on
how to make it as good as it was
intended to be (or even better!)
www = structure + layout =
markup + style =
XHTML + CSS
Designing with web standards
ensures forward-compatibility!
Story of www (3W)
Sir Tim Berners-Lee
December, 2003:
Announcements from Buckingham Palace and
the World Wide Web Consortium (W3C)
proclaim that Queen Elizabeth II will make
Tim Berners-Lee, W3C Director, a Knight
Commander of the Order of the British
Empire.
"The rank of Knight Commander is the second
most senior rank of the Order of the British
Empire, one of the Orders of Chivalry
awarded. Tim Berners-Lee, 48, a British
citizen who lives in the United States, is being
knighted in recognition of his services to the
global development of the Internet through the
invention of the World Wide Web."
Story of WWW
In 1980, while Berners-Lee worked as a
consultant software engineer at CERN, the
European Particle Physics Laboratory in
Geneva, he wrote for his own private use his
first program for storing information using the
kind of random associations the brain makes.
The "Enquire" program -- which was never
published -- formed the conceptual basis for
the future development of the Web.
While at CERN in 1989, he proposed a global
hypertext project to be known as the World
Wide Web. Based on the earlier "Enquire"
work, it was designed to allow people to work
together by combining their knowledge in a
Web of hypertext documents.
Tim Berners-Lee meets Kofi Annan
during the WSIS, Geneva 2003
Story of WWW
Berners-Lee wrote the first World Wide Web
server, httpd, and the first client, "World
Wide Web," in October 1990. He also wrote
the first version of the document formatting
language with the capability for hypertext
links, known as HTML.
The program "WorldWideWeb" was first
made available within CERN in December
1990, and the first successful
demonstration of the Web clients and
servers working over the Internet was made
that same month. All of his code was made
available on the Internet at large in the
summer of 1991.
The very first webserver
(a Next Cube at CERN)
Story of WWW
From 1991 to 1993, Berners-Lee continued
working on the design of the Web, coordinating
feedback from users across the Internet. His
initial specifications for URIs, HTTP and HTML
were refined and discussed in larger circles as
the Web technology spread.
In 1994, with support from the Massachusetts
Institute of Technology (MIT), Berners-Lee
founded the World Wide Web Consortium,
where he presently serves as director. The
W3C coordinates Web development worldwide.
Its goal is to lead the Web to its full potential,
ensuring its stability through rapid evolution
and revolutionary transformations of its usage.
Carlo at the WSIS, playing
with the first webserver ;-)
HTML: a definition
“HTML is an authoring language that defines the structure and
layout of a Web document by using a variety of tags and attributes”
HyperText Markup Language
Hypertext: it’s a way to link
together documents with crossreferences, adding a logical structure
to the information.
Markup Language: it’s a way to
add computer-understandable
information to text files. Certain parts
of the text file are interpreted as
markup instead of content. This markup
may contain instructions for the
computer. The interpretation of those
instructions is defined by the semantics
of a particular markup language.
HTML, XHTML, SMIL are examples of
markup languages.
structure or layout?
At the beginning HTML was
supposed to define only the
structure (hypertext, semantic).
It has been later adapted to
provide also graphical layout
information (appearance).
These two functions doesn’t mix
well together because of the
different behaviors of the many
browsers (browser’s war and
the broken standard...)
structure with layout
W3C developed a
solution that meet the
need of standard-compliant
tools to design nice-appealing
and well-structured websites:
XHTML for the semantic
structure
Cascading Style Sheets (CSS)
for the graphical layout
designing for web
The easiest way to ensure optimal
rendering of your web pages in any
browser is by following the standards.
Doing so will guarantee optimal rendering
in all standard-compliant modern browsers
like the recent versions of Mozilla, Opera,
Netscape, Internet Explorer, being them
for Linux, Windows, Macintosh, etc...
Of course, each of these browsers has its
own minor quirks or legitimate differences
of interpretation, so testing your site in all
of them is still mandatory.
Old version of browsers are also partially
supported, with some limitation.
Designing with standards
Start here:
http://developer.apple.com/internet/
webcontent/bestwebdev.html
Follow the guide of Jeffrey Zeldman:
http://www.zeldman.com/dwws/
and his famous mailing list, A LIST APART:
http://www.alistapart.com/
Books on CSS:
http://www.meyerweb.com/eric/
books/css-tdg/
http://www.christopherschmitt.com/
books/cssbook/
Books on XHTML:
http://www.oreilly.com/catalog/
Thank you
for your attention!
Any question?
http://arpl.ictp.trieste.it