Transcript Ch.3 - WINSLab

Ch 3. Wireless Internet,
Mobile IP and Wireless Web
Myungchul Kim
[email protected]
• Internet
• IP Overview
• Mobile IP
• Basic Web
• Semantic Web and XML
Figure 2: Getting Information over web
Wireless
Browser
4
Wireless
Network
Wireless
Gateway
http
5
Web
Server
2
1
Web
Browser
http
over
wired Internet
Web
Gateway
3
Content
(XML/HTML)
Back-end
Systems
and
Darabases
1. Access from Web browser to Web Server over wired Internet
2. Access Web contents from HTML/XML files
3. Access to non-Web content through a Wen gateway
4. Access from cellular phone over a wireless network
5. Access from wireless gateway to Web Server over wired Internet
Computer 1
Computer 2
Telnet FTP SMTP HTTP
TCP
Others
UDP
Telnet FTP SMTP HTTP Other
TCP
UDP
IP
IP
Physical Network
Physical Network
Partial View of Internet
arts.um.edu
108.2.11.7
www.sun.com
75.10.17.3
IP
WAN3
IP
www.IBM.com
WAN2
Switch
/Gateway
cs.um.edu
108.2.11.5
75.10.17.1
Switch/Gateway
Switch/Gateway
IP
WAN1
Bank1.co..uk
(Typically
ATM,
83.13.17.3
Frame Relay,
Level3.co..uk
X.25)
83.13.17.4
•DNS (Domain Name Services) translates cs.um.edu to 108.2.11.5
•Telnet cs.um.edu = Telnet 108.2.11.5
•FTP cs.um.edu = FTP 108.2.11.5
Network Categories
LAN
LAN
MAN
WAN
LAN
LAN
LAN
MAN
LAN
* wide area network (WAN): common carrier, long distance, typically 56 kbps
* local area networks (LAN): no common carrier, short distance, upto 100 mbps
* metropolitan area networks (MAN): LAN of a city
Network Convergence to IP
Applications
(Data, Voice, Video)
Internet Protocol (IP)
Currently IPv4, Future IPv6
Network Technologies
(Ethernet, Token Ring, Wireless, ATM,
Frame Relay, X.25, FDDI, and many more)
NGN is IP-Based (“IP Dialtone”)
Data Applications
(typically Web based)
Telnet
FTP
SMTP
Voice and Video
Applications
HTTP
DNS
Others
UDP
TCP
(User Datagram Protocol)
(Transmission Control Protocol)
H.323
(ITU)
SIP
(IETF)
Other Transport
Protocols
IP
(Internet Protocol)
F-Ethernet FDDI
X.25
ATM
Frame Relay
Sonet (150 Mbps to 100 Gbps)
Other
Physical
Networks
Mobile IP
• Enable computers to maintain Internet
connectivity while moving from one Internet
attachment point to another
• Mobile – user's point of attachment changes
dynamically and all connections are automatically
maintained despite the change
• Nomadic - user's Internet connection is terminated
each time the user moves and a new connection is
initiated when the user dials back in (traveler)
– New, temporary IP address is assigned
• How is this different from DHCP
NSP and ISPs
Mainframe
NSP POP
POP
IP
Network
ISP (POP
+ Web services)
Dialup
•POP(Point of Presence) provided by an NSP only provides a
local phone access. The user can choose an ISP
•An ISP provides an IP address (user dials in)
•When the user moves, has to disconnect and redial again.
Operation of Mobile IP
•
Mobile IP goal is to allow users to seamlessly roam from
private networks (e.g. Ethernet, wireless LANs) to public
networks.
• Mobile node is assigned to a particular network –
home network
• IP address on home network is static – home
address
• Mobile node can move to another network – foreign
network
• Mobile node registers with network node on foreign
network – foreign agent
• Mobile node gives care-of address to agent on home
network – home agent
Mobile IP Scenario
Mobile Node A
NSP POP
Home Network
for A
Foreign
Agent
2
Home
Agent
IP
1
Network
5
ISP Servers
3
NSPForeign
POP
4
Network
for A
Capabilities of Mobile IP
• Discovery – mobile node uses discovery
procedure to identify prospective home and
foreign agents
• Registration – mobile node uses an
authenticated registration procedure to
inform home agent of its care-of address
• Tunneling – used to forward IP datagrams
from a home address to a care-of address
Registration
UDP
Discovery
ICMP
IP
Tunneling
–
two ways to acquire a care-of address
•
•
–
the care-of address is an IP address of the foreign agent: it
allows many mobile nodes to share the same care-of address.
A colocated care-of address is a care-of address acquired by
the mobile node as a local IP address (through DHCP)
rough outline of the operation of the Mobile IP
protocol
1.
mobility agents advertise their presence via agent
advertisement messages. A mobility node may optionally
solicit an agent advertisement message by using an agent
solicitation message.
2. A mobile node receives an agent advertisement and determines
whether it is on its home network or a foreign network.
3. When the mobile node detects that it is located on its home
network, it operates without mobility services. If returning to
its home network from being registered elsewhere, the
mobile node deregisters with its home agent through a
variation of the normal registration process.
4. When a mobile node detects that it has moved to a foreign
network, it obtains a care-of address on the foreign network.
5. The mobile node, operating away from home, then registers its
new care-of address with its home agent through the
exchange of a registration request and registration reply
message.
6. Datagrams sent to the mobile node’s home address are
intercepted by its home agent to the mobile node’s care-of
address, received at the tunnel endpoint and finally delivered
to the mobile node.
7. In the reverse direction, datagrams sent by the mobile node
may be delivered to their destination using standard IP
routing mechanisms, without necessarily passing through the
home agent.
• Ongoing work and open questions
– Routing inefficiencies
• Triangle routing
• Route optimization
– Security issues
• Firewalls
• Such communications, originating from the mobile node, carry the
mobile node’s home address, and would thus be blocked by the
firewall.
–
–
–
–
Ingress filtering
User perceptions of reliability
Slow growth in the wireless LAN market
Current development efforts
• Vertical handoffs between dissimilar media
• Ad-hoc networking
Web and XML
•Basic Web
– HTML
–Web browsers
–Web servers
–HTTP
•Next Generation Web and XML
–XML and other markup languages
–Object-orienting the Web
World Wide Web
• WWW is a collection of middleware that
operates on top of the Internet.
• WWW middleware supports the growing
number of users and applications
• Basic WWW middleware is based on a few
simple concepts and technologies
–
–
–
–
–
–
Web servers
Web browsers
Uniform Resource Locator (URL)
Hypertext Transfer protocol (HTTP)
Hypertext Markup Language (HTML)
Gateways to non-Web resources
World Wide Web Overview
EC/EB Applications
World Wide Web Middleware
(Web browsers, Web Servers,
HTTP, HTML, Web Gateways)
IP Network Stack
…FTP, Telnet, SMTP, SNMP, NFS, and Others
TCP
UDP (User Datagram
(Transmission Control Protocol)
Protocol)
Internet Protocol (IP)
Physical
Network
USWeb Professional Certification
Legacy Systems and the Web
Example of Web
UNIX
Web Browser
(Hot JAVA)
Web
Search
Tools
HTTP
Macintosh
PC
Web Browser
(Netscape)
Web Browser
(Explorer)
HTTP
HTTP
Web Site www.books.com
Web Site cs.uc.edu
o Web server (program)
o HTML Documents
o Gateway for Database Access
o Web server (program)
o HTML Documents
o (Faculty.html,
courses.html)
Databases
URL: http://cs.um.edu/faculty.html
Web Servers
•
•
•
•
Web servers provide the content for Web users.
Web servers are populated by the content providers.
Conceptually: a Web server is a catalog of information
In reality: a Web server is
– Server software (e..g., Apache)
– a collection of HTML files
– Gateways to non-HTML resources (CGI, Servelet,,)
• In many cases, a machine is dedicated/designated as a
Web server .
• Convention: content providers begin with designated
"home pages"
• Home pages include company logo, fancy artwork for
attention, special deals, overviews, pointers to additional
information, etc.
First Generation Web Architectures
(HTML, HTTP, CGI)
Web
Browser
Web
Site
HTTP
Web
Server
HTML
Displays
CGI
HTML Docs
Corporate
Databases
and
Applications
Semantic (Next Generation) Web
• Many developments
• Key idea: expanding the scope from human
interactions to machine interactions
• HTML to XML : exchange formats
• HTTP to HTTP-NG: State handling
• Improved programmability:
– Access remote objects
– Object view (Document Object Model)
– Many others (detailed programmability, digital
signatures)
• Reference: www.w3.org
Next Generation Web Model Key Players
XML
Semantic identification of fields
Resource Description
Framework (RDF)
Metadata and Data Type
Facilities
Document Object Model
(DOM)
Behavior and Behavior Attachments
Protocols and Messaging
Web-IDL, HTTP-NG,
XML (eXtensible Markup Language)
•
•
•
•
Gaining importance for common data representation
“Simpler” than SGML (subset of SGML)
More “general” than HTML
Example:
<CUSTOMER>
<NAME> Joe </NAME>
<ADDRESS> NY </ADDRESS>
</CUSTOMER>
• Great deal of activity in Ecommerce (competition to EDI),
messaging middleware, data transformers, data
management, publishing, etc.
XML Family
XML
DTD
for Validation
Variants
WML (wireless)
VML (voice)
MathML
...
Other features of XML
•XML Link
•XML Signature
•XML Path (point to
specific sections of docs)
XSL
for
Presentation
XML
(Extensible
Markup
Language)
XML
Query
Language
XML
Schema for
Data Representation
Customer Record in XML
<?xml version=“1.0” standalone=“yes”?>
<customer>
<name>
<first>Amjad</first>
<last>Umar</last>
</name>
<address>
<street>MCC-1C337B</street>
<street>445 South Street</street>
<city>Morristown</city><state>NJ</state>
<zip>07960</zip>
</address>
<phone>973-829-3114</phone>
</customer>
XML Tree
Customer
First
Phone
Address
Name
Last
Street
City
State
Zip
Well-formed versus Valid
• A Well-Formed Document:
– adheres to the syntactic rules defined by the XML standard
• E.g. Tags are delimited by < and >
• A Valid Document:
– A well-formed document that also adheres to the rules of a
specified Document Type Definition (DTD)
• DTD:
– specifies a set of rules for the structure of the document
Well-formed
Valid
DTD
A DTD for a Customer
<!ELEMENT
<!ATTLIST
<!ELEMENT
<!ELEMENT
<!ELEMENT
<!ELEMENT
<!ELEMENT
<!ELEMENT
<!ELEMENT
<!ELEMENT
<!ELEMENT
<!ELEMENT
customer (name, address?, phone?)>
customer id CDATA #REQUIRED>
name (first, middle?, last)>
address (street+, city, state, zip)>
phone (#PCDATA)>
first (#PCDATA)>
middle (#PCDATA)>
last (#PCDATA)>
street (#PCDATA)>
city (#PCDATA)>
state (#PCDATA)>
zip (#PCDATA)>
… We can save this into a file called customer.dtd
Note: PCDATA cannot have XML tags
Valid XML document
<?xml version=“1.0” standalone=“no”?>
<!DOCTYPE customer SYSTEM “customer.dtd”>
<customer id=“12345”>
<name>
<first>Amjad</first>
<last>Umar</last>
</name>
<address>
<street>MCC-1C337B</street>
<street>445 South Street</street>
<city>Morristown</city><state>NJ</state>
<zip>07960</zip>
</address>
<phone>973-829-3114</phone>
</customer>
Well-formed but not Valid XML document
<?xml version=“1.0” standalone=“no”?>
<!DOCTYPE customer SYSTEM “customer.dtd”>
<foo1 id=“12345”>
<foo2>
<foo3>Amjad</foo3>
<foo4>Umar</foo4>
</foo2>
<foo5>
<foo6>MCC-1C337B</foo6>
<foo7>445 South Street</foo7>
<foo8>Morristown</foo8><foo9>NJ</foo9>
<foo10>07960</foo10>
</foo5>
<foo11>973-829-3114</foo1>
</foo1>
XSL
How to run example:
c:\>xt customer.xml transform.xsl customer.html
XSL
Processor
XML
Document
XSL
Stylesheet
<xsl>
<rule>
<target-element type=customer/>
<HTML>
<BODY>
XSL
<children/>
Stylesheet
</BODY>
</HTML>
</rule>
</xsl>
XSL
Processor
XSL
Processor
XSL
Processor
HTML
MS
Word
email
EDI
W3C Web Architecture
SMIL
SVG (scalable
Vector Graphics)
MathML
HTML
HTTP
PICS
P3P
Others
DOM
Resource Description
Framework (RDF)
XML
PICS: Platform for Internet Content Specification
P3P: Platform for privacy preferences
SMIL: Synchronous Multimedia Interaction Language
DOM: Document Object Model
Concluding Comments
• Internet and Web are foundation of Ecommerce
• Basic components of Web (HTML, HTTP, Browsers, Servers)
• Web is proceeding in several directions
• We have discussed two:
– Improving human access
– XML
– Web automation
• Issue: will Web become too complex
References:
• www.w3.org
• IEEE Internet Computing, January 1999