Ch 3. Wireless Internet, Mobile IP and Wireless Web

Myungchul Kim

mckim@icu.ac.kr

• Internet • IP Overview• Mobile IP• Basic Web• Semantic Web and XML

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>

XML Tree

Customer

Name

First Last

Address

Street City State Zip

Phone

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

email

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