Transcript Course Outline

M-commerce
• Wireless Application Protocol (WAP)
– http://www.webproforum.com/wap/index.html
– provides web-like services in wireless domain
• To operators
– improving existing services
• better interface to voice mail
– new value-added services
• banking, stock info, entertainment info
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M-commerce
• To content providers
– Using the same model as the Internet
– Applications are written in tag-based wireless
markup language (WML), which is a subset of
extensible markup language (XML)
– 100 million WAP
• To end users
– easy access to information and services such
as stock prices, news, weather, and travel
information through their mobile devices
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M-commerce
• M-commerce
– expects to have an even far reaching impact to
society than Internet
• Why?
– Because not everybody can use a computer to
access Internet
– but everybody know how to use a mobile
phone
• mobile phone has the potential to capture
75% of the population
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M-commerce
• WAP
– is a global standard for mobile network
– founded in 1997 by companies like Ericsson,
Nokia, and Motorola
– similar to the Internet model, the wireless
device contains a microbrowser, while content
and applications are hosted on servers.
– applications are written in tag-based wireless
markup language (WML)
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M-commerce
• WAP is similar to HTTP/TCP/IP
– but TCP is inefficient over mobile networks
– so WAP has its own transport layer (like TCP)
• WAP phone cannot be connected to web directly!
– similar to HTTP/TCP/IP only in concept, it has
different implementation !!
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M-commerce
• Because WAP uses different format for its data,
packet sent by WAP will not be understandable
by TCP/IP based machines
– it is like document produced by Microsoft and
Apple, the formats are different
• using the same analogy, if Microsoft Word wants
to read a document in Apple format, it needs to
translate the document format
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M-commerce
• WAP phone users can only access Internet via a
WAP Gateway
– basically a machine that translate the WAP
packet format to IP format
• The incompatibility is probably by design !!
– less competition!
– Operators cannot use IP-based routing
equipment, they must buy it from Ericsson,
Nokia, Motorola, . . .
• For end users
– currently can only access network provided by
their service providers
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M-commerce
• Competition for WAP protocols
– subscriber identity module (SIM) toolkit
• use of SIMs or smart cards
• Windows CE
– from Microsoft
• JavaPhone
– Sun Microsystems
– embedded in a Java virtual machine on the
handset
• NTT Docomo
– huge customer base in Japan
– support IP, can access to Internet directly
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Future
• Third generation mobile communication
• W-CDMA (wideband CDMA)
– 1.5 M bits per second
• Applications
– mobile multimedia
– phone may attach a video camera
• video conferencing
• sends picture to home while you are
traveling
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Not everything is rosy
• Satellite phone
• Different from mobile
– uses a large number of satellite to cover the
entire world
– can make call anywhere as long as there is a
satellite above you
• top of Everest
• In contrast, cellular phone
– uses a large number of base stations to cover
a city
– can only make call when there is a base station
nearby
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Recent disaster
• Satellite phone
– One of the biggest blunder ever !!
• Demise of Motorola Iridium project
– a satellite network
• 66 low-order satellite covers the entire
globe
– only in operation for one year
• DON’T buy those satellite phone in Mong Kok
– easily identifiable by its large size
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Lab session - application protocol
• Hyper Text Transfer Protocol (HTTP)
• telnet www.cuhk.edu.hk 80
• GET http://www.ie.cuhk.edu.hk/index.html HTTP/1.0
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SMTP (Simple Mail Transfer Protocol)
•
•
SMTP - an ASCII protocol for transferring emails from host to
destination`s mail server, e.g., to send a mail to me:
> telnet ie.cuhk.edu.hk 25
;TCP connection to mail daemon
220 eng.ie.cuhk.edu.hk ESMTP ;reply from ie mail server
MAIL FROM: [email protected]
250 [email protected] . . . Sender OK ;server reply
RCPT TO: [email protected]
250 [email protected] . . . Recipient ok
DATA
354 Enter mail, end with ``.`` on a line by itself
. . . email body
.
QUIT
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SMTP (Simple Mail Transfer Protocol)
• Mail bomb
– large volume of junk mails intended to flood
the buffer space of the mail server
– sender's name is easy to disguise
• mail server does not verify the sender
address
• “MAIL FROM: “ field, you can put it anything
you like
– it is still possible to trace the IP address of the
sender`s station from the system's log
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POP3 (Post Office Protocol) (RFC1225)
• To fetch mail from a remote mailbox
– incoming mails are stored in the mail server
– > telnet ie.cuhk.edu.hk 110
+OK QUALCOMM Pop server ready
user mchang
+OK Password required for mchang
pass ********
+OK mchang has 2 message(s) (1351 octets)
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POP3 (Post Office Protocol) (RFC1225)
list
+OK 2 messages (1351 octets)
1 869
2 482
retr 1
+OK 869 octets
Received: from . . .
...
dele 1
+OK Message 1 has been deleted
quit
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