ch 3. wireless internet, mobile ip and wireless web myungchul kim [email protected]
TRANSCRIPT
Figure 2: Getting Information over web
WebServer
Content(XML/HTML)
Back-endSystemsandDarabases
httpoverwired Internet
WirelessGatewayWireless
Network
http
WirelessBrowser
WebBrowser
WebGateway
1
2
3
4
5
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 gateway4. Access from cellular phone over a wireless network5. Access from wireless gateway to Web Server over wired Internet
IP
Physical Network
Telnet FTP SMTP HTTP
TCP UDP
Others
IP
Physical Network
Telnet FTP SMTP HTTP
TCP UDP
Others
Computer 1 Computer 2
IP
WAN1
(Typically
ATM,
Frame Relay,
X.25)
Switch/Gateway
IP
WAN2
IP
WAN3
Switch/Gateway
Switch/Gateway
83.13.17.3
83.13.17.4
Bank1.co..uk
Level3.co..uk
75.10.17.1
75.10.17.3
www.IBM.com
www.sun.com
108.2.11.5
108.2.11.7
cs.um.edu
arts.um.edu
Partial View of Internet
•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
WAN
MANLAN
LAN
LAN
MANLAN
LAN
LAN
Network Categories
* 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
Network Technologies (Ethernet, Token Ring, Wireless, ATM,
Frame Relay, X.25, FDDI, and many more)
Internet Protocol (IP)Currently IPv4, Future IPv6
Applications(Data, Voice, Video)
IP(Internet Protocol)
TCP(Transmission Control Protocol)
UDP(User Datagram Protocol)
Telnet FTP SMTPH.323 (ITU)
SIP (IETF)
F-Ethernet FDDI X.25 ATM Frame Relay Other Physical Networks
Other Transport Protocols
HTTP
NGN is IP-Based (“IP Dialtone”)
Sonet (150 Mbps to 100 Gbps)
Voice and VideoApplications
Data Applications (typically Web based)
DNS Others
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
IP
Network
Mainframe
ISP (POP+ Web services)
POP NSP POP
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
IP
Network
ISP Servers
NSP POPHome Networkfor A
NSP POPForeign Networkfor A
Mobile Node A
ForeignAgent
HomeAgent
1
2
3
4
5
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
IP
UDP ICMP
Registration Discovery 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 protocol1. 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
USWeb Professional Certification Legacy Systems and the Web
World Wide Web OverviewEC/EB ApplicationsEC/EB Applications
World Wide Web MiddlewareWorld Wide Web Middleware(Web browsers, Web Servers,(Web browsers, Web Servers,
HTTP, HTML, Web Gateways)HTTP, HTML, Web Gateways)
……FTP, Telnet, SMTP, SNMP, NFS, and OthersFTP, Telnet, SMTP, SNMP, NFS, and Others
TCPTCP(Transmission Control Protocol)(Transmission Control Protocol)
Internet Protocol (IP)Internet Protocol (IP)
PhysicalPhysicalNetworkNetwork
IP Network StackIP Network Stack
UDP (User DatagramUDP (User DatagramProtocol)Protocol)
Example of Web
WebWebSearchSearchToolsTools
Web BrowserWeb Browser(Hot JAVA)(Hot JAVA)
Web BrowserWeb Browser(Netscape)(Netscape)
Web BrowserWeb Browser(Explorer)(Explorer)
Web Site www.books.comWeb Site www.books.com
o Web server (program)o Web server (program)o HTML Documentso HTML Documentso Gateway for Database Accesso Gateway for Database Access
Web Site cs.uc.eduWeb Site cs.uc.edu
o Web server (program)o Web server (program)o HTML Documentso HTML Documentso (Faculty.html,o (Faculty.html, courses.html)courses.html)
DatabasesDatabases
UNIXUNIX MacintoshMacintosh PCPC
HTTPHTTP HTTPHTTP HTTPHTTP
URL: http://cs.um.edu/faculty.htmlURL: 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)
HTML DocsHTML Docs
CGI CorporateDatabasesand Applications
HTTP
HTMLDisplays
Web Web BrowserBrowser
WebWebSiteSite
WebWebServerServer
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(Extensible Markup Language)
VariantsWML (wireless)VML (voice)MathML...
XSL for Presentation
Other features of XML•XML Link•XML Signature•XML Path (point to specific sections of docs)
XMLQuery Language
XMLSchema forData Representation
XMLDTDfor Validation
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>
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
DTD
Valid
A DTD for a Customer<!ELEMENT customer (name, address?, phone?)>
<!ATTLIST customer id CDATA #REQUIRED>
<!ELEMENT name (first, middle?, last)>
<!ELEMENT address (street+, city, state, zip)>
<!ELEMENT phone (#PCDATA)>
<!ELEMENT first (#PCDATA)>
<!ELEMENT middle (#PCDATA)>
<!ELEMENT last (#PCDATA)>
<!ELEMENT street (#PCDATA)>
<!ELEMENT city (#PCDATA)>
<!ELEMENT state (#PCDATA)>
<!ELEMENT zip (#PCDATA)>
… We can save this into a file called customer.dtdNote: 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
XMLDocument
XSLStylesheet
XSLProcessor
HTML
XSLProcessor
MSWord
XSLProcessor
XSLStylesheet
XSLProcessor
EDI
<xsl><rule><target-element type=customer/><HTML>
<BODY><children/>
</BODY></HTML></rule> </xsl>
How to run example:c:\>xt customer.xml transform.xsl customer.html
W3C Web Architecture
XML
HT
ML
MathM
L
SV
G (scalable
Vector G
raphics)
SM
IL
Resource DescriptionFramework (RDF)
P3PPICSOthers
PICS: Platform for Internet Content SpecificationP3P: Platform for privacy preferencesSMIL: Synchronous Multimedia Interaction LanguageDOM: Document Object Model
HTTP DOM
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