Transcript The Internet

MD253 - E-Commerce
Module 1: A World Connected
Spring 2003
The Internet, consumer devices, iTV
How the Internet Works
Telecom: an Industry in Crisis
Solving the Last Mile Problem
Mobile & Wireless
Emerging & Key Technologies
What is the Internet?
• A Network of Networks
– TCP/IP - standard protocol for routing & transport
• A medium of exchanging all form of digital
data
– text, graphics, audio, video, programs, faxes
• An infrastructure for various services
– e-mail (electronic mail)
– WWW (world wide web)
– FTP (file transfer protocol)
– UseNet newsgroups
– Games, EDI, etc.
How Many Online?
Region
Europe
Asia/Pacific
Canada & USA
Latin America
Africa
Middle East
World Total
# Online
190.91 million
187.24 million
182.67 million
33.35 million
6.31 million
5.12 million
605.60 million
source: nua.ie
BSkyB
Moxi
TiVo
xbox
Lyra
Samsung
Media Center
Smart Display
AOLtv
Replay
Ultimate TV
XP Media Center
Transmission Speeds
• Bandwidth
– measure of transmission speed / capacity
• Bits & Bytes
– bit - smallest form of computer memory - 1 or 0
– byte - 8 bits, roughly 1 character (Latin alphabet)
• How do we measure speeds?
– bps - bits per second
– Kbps - kilobit, thousands of bits per second
– Mbps - megabit, millions of bits per second
– Gbps - gigabit, billions of bits per second
Anatomy of a URL
• URL
– Uniform Resource Locator (web address)
http://www2.bc.edu/~gallaugh/directory/file.html
application
protocol
(http is
assumed
by current
browsers).
Others:
FTP, NNTP
host
computer
(others
@ BC:
agora,
www)
domain user
ID
name,
top
level
domain
directory
case sensitive
file
The DNS & IP Addresses
• IP Address
– Unique number identifying Internet computers. Expressed
as four numbers between 0 and 255.
– ex: www.bc.edu = 136.167.2.72 (32 bit address)
– IPv6: 128 bit addressing, more efficient/faster, secure
• DNS - Domain Name Service
– A distributed database used to translate host/domain
names, into Internet Protocol (IP) Addresses.
• Registry of an Internet domain name:
– for com, net, org, over 60 firms (see icann.org for list)
– for country-specific domains (.jp,.uk, .tv) fees vary widely
(see icann.org for list)
Network Interconnections
dial-in
web server
www2.bc.edu users (56.6 Kbps)
modem pool
R
dorm
users
dorm LAN
class/office
users
office LAN
wireless
BC Campus Network Backbone (10 Mbps)
(IP #s 136.167.xxx.xxx domain)
Internet Leased Line through our ISPs (45 Mbps / T3)
The
Internet
microsoft.com
whitehouse.gov
local ISP
TCP/IP
• TCP/IP - the Internet’s common
language
• TCP - Transmission Control Protocol.
Breaks up transmissions (e-mail
messages, web pages, etc.) into
packets of no more than about 1500
characters each, checks the integrity of
incoming packets, and reassembles
packets on the other end
• IP - Internet Protocol. Routes packets.
Packet Traffic
• What’s in a packet?
– source address
– destination address
– error checking (checksum)
– time to live
– options (timestamp, record route, etc.)
– your data!
A Packet Switched Network at
Work
packet1
R
E-mail
message:
Prof. Gallaugher,
I just wanted to let
you know that I got
a job based on the
stuff I learned in
your class...
packet1
packet2
packet2 R
packet3
packet3
R
R
= router
R packet1
R
packet2
packet2
packet3
packet3
E-mail
message:
Prof. Gallaugher,
I just wanted to
let you know ...
US Internet Infrastructure
Watch Cable & Wireless’s backbone traffic at:
traffic.cwusa.com
Source: [email protected]
TCP vs. UDP
TCP - perfect transmission is critical (e.g. e-mail)
TCP will request packets that are lost or
damaged
The Internet
UDP = User Datagram Protocol
UDP - low latency is critical (e.g. streaming audio, video)
Latency matters - UDP will ignore packets that
don’t arrive on time or in good shape
The Internet
Circuit vs. IP Telephony
Circuit Switching
Guaranteed QoS (quality of service)
Internet Telephony (e.g. Vonage, Net2Phone)
packets over the Internet, variable QoS
The Internet
IP Telephony over Private Networks (e.g. corporate VoIP, Qwest)
packets over private network, improved QoS
Private IP Network
87% Decline
in
International
DS-3
Pricing over
the past two
years
Source: BandXChange
67% Decline
in Domestic
DS-3
Pricing over
the past two
years
Source: BandXChange
The Last Mile Problem
• The contenders
– Cable Modems (cable firms)
• Tech limits:congestion (shared capacity with local users)
– DSL (RBOCs & those leasing capacity)
• Tech limits:distance (must be 3.5 miles from central office
for ADSL), home wiring limitations
– Terrestrial Fixed Wireless (WorldCom, Sprint,
others)
• Tech limits: line-of-sight, rain fade, antennas, congestion
– GEO Satellite (Hughes, EchoStar)
• Tech limits: slower transmission, latency, need dish, lineof-sight, congestion
i-Mode’s Rocket Ride
Mobile Contrasts
Europe
• poor technology
• “walled gardens”
• enormous capital
outlays
Japan
• packet-switched,
always on, HTML
standards, java
• open platform
• 3G licenses offered
for free via “beauty
contests”
Emerging Wireless Technologies
• Wi-Fi
– 802.11b – LAN replacement, 11 Mbps, 150-300 ft.,
crowded, unregulated 2.4 GHz spectrum
– 802.11a (Wi-Fi 5) – 54 Mbps, similar range, less crowded 5
GHz spectrum, 802.11g – 54 Mbps, rev. compatible w/(b)
• Bluetooth
– Cable replacement technology
– 400-700 Kbps, 30-33 ft., unregulated 2.4 GHz spectrum
• UWB – Ultra Wide Band
– 100 Mbps+, 30 ft., multiple spectra (licensed &
unregulated)
• RFID
– Tracking, payment, bar-code replacement
– Current high cost $1-$2+, privacy concerns