Internet Applications and Distributed Data Processing

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Internet Applications and Distributed Data
Processing

• Topic 2

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Outline

• Internet Applications
• The Internet
• Internet applications
• Network Models
• Distributed Data Processing
• Network Architectures
• Network Configurations

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Internet Applications
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Internet Applications

• There are four important Internet application
  software tools
• the Web
• electronic mail (e-mail)
• FTP
• Telnet

Less important applications WAIS, gopher
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World Wide Web

• One of the fastest growing Internet software
  applications is the World Wide Web.
• The Web was first conceived in 1989 by Tim
  Berners-Lee at the European Laboratory for
  Particle Physical (CERN) in Geneva.
• CERNs first Web browser was written in 1990, but
  it was 1991 before it was available on the
  Internet for other organizations to use.

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World Wide Web

• In 1993, Marc Andeessen, a student at the
  University of Illinois, led a team of students
  that wrote Mosaic, the first graphical Web
  browser, as part of a project for the
  universitys National Center for Supercomputing
  Applications (NCSA)
• In 1994, Andreessen and some colleagues left NCSA
  to form Netscape.

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WWW Sites Growth
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How the Web Works
Server computer with Web Server software
HTTP Request
Client computer with Web Browser software
HTTP Response
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How the Web Works

• Each client computer needs a Web browser.
• Each server needs a Web Server.
• Web address Internet Uniform Resource Locator
  (URL)
• The protocol for communication between a Web
  browser and a Web server Hypertext Transfer
  Protocol (HTTP).
• Web page design language Hypertext Markup
  Language (HTML)

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How the Web Works
Command URL HTTP version
GET http//tcbworks.cba.uga.edu/adennis/res.htm
HTTP/1.1 Date Mon 03 Aug 1998 173546
GMT User-Agent Mozilla/3.0 From
adennis_at_uga.cc.uga.edu Referer
http//tcbworks.cba.uga.edu/adennis/home.htm
- Request Line
- Date
- Web browser (this is Netscape)
Request Header
- Users e-mail address
URL that contained the link to the requested
URL (Request body is optional here)
A Request from a Web browser to a Web server
using the HTTP standard
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A response from a Web server to a Web browser
using the HTTP standard
HTTP version Status code Reason phrase
HTTP/1.1 200 OK Date Mon 03 Aug
1998 173546 GMT Server NCSA/1.3 Location
http// tcbworks.cba.uga.edu/adennis/res.htm Cont
ent-type text/html lthtmlgt ltheadgt lttitlegtBusiness
Data Communications and Networking Web Resources
lt/titlegt lt/headgt ltbodygt ltH2gtResources on the Web
lt/H2gt ltPgtThis section contains links to other
resources on the WEB that pertain to the field
of data communications and networking
lt/Pgt lt/bodygt lt/htmlgt
- Date
- Web server
Response Header
- URL
- Type of file
Response Body
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Internet Search Engines

• Search engines are Web sites that routinely use
  software spiders to explore the Web. There are
  literally dozens of search engines and
  directories on the Web. Three of the best are
• Yahoo (http//www.yahoo.com)
• Altavista
• Google
• (More netscape, GoTo.com, HotBot, Snap,
  About.com, Lycos, LookSmart)
• A metasearch engine (like MetaCrawler
  http//www.metacrawler.com) simultaneously sends
  requests to many search engines and then
  integrates the responses.

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E-mail Clients Servers
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E-mail Standards

• Mail Transfer Agents
• Three most commonly used standards are
• SMTP (Simple Mail Transfer Protocol)
• X.400 (developed by CCITT in 1984).
• CMC (Common Messaging Calls, a simpler version of
  the X.400 standard, developed by CCITT with IBM,
  Lotus and Microsoft in 1994.)
• All three e-mail standards work in the same basic
  fashion.

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E-mail Standards

• User agents
• Post Office Protocol 3 (POP3), which defines how
  operate and how messages to and from mail
  transfer agents are formatted.
• Internet Mail Access Protocol (IMAP).
• Non-text message transmission
• Multipurpose Internet Mail Extension (MIME),
  uuencode and binhex.

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How the SMTP e-mail works
Server computer with e-mail server
software (message transfer agent)
SMTP packet
Client computer with e-mail client
software (user agent)
LAN
SMTP packet
Internet
SMTP packet
Server computer with e-mail server
software (message transfer agent)
IMAP or SMTP packet
Client computer with e-mail client
software (user agent)
LAN
SMTP packet
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How web-based e-mail works
Server computer with Web server software
HTTP request
Client computer with Web browser
SMTP packet
Server computer with mail server software
LAN
SMTP packet
HTTP response
Internet
Server computer with mail server software
SMTP packet
HTTP request
Client computer with Web browser
LAN
IMAP or SMTP packet
HTTP response
IMAP packet
Server computer with Web server software
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How the Instant Messaging works
IM packet
Client computer with e-mail client
software (user agent)
LAN
IM packet
Server computer with IM server software
LAN
IM packet
Internet
Client computer with IM client software
IM packet
LAN
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E-mail Directories

• Before you can send an e-mail message, you must
  know the receivers e-mail address. Currently
  there are no universal e-mail directories.
• X.500 is the directory service for X.400 mail
  users, but at present there are few standard
  application software packages that conform to
  X.500.
• Lightweight Directory Access Protocol (LDAP) is a
  subset of X.500.

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Other Network Applications

• Groupware
• Discussion groups (e.g. listserv)
• Document-based groupware
• Group support systems
• Videoconferencing. Provides real-time
  transmission of video and audio signals to enable
  people in two or more locations to have a
  meeting.

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Listserv

• Listserv group is similar in concept to the
  usenet newsgroups but is generally less formal.
• One part, the listserv processor, processes
  commands such as requests to subscribe,
  unsubscribe, or to provide more information about
  the listserv.
• The second part is the listserv mailer. Any
  message sent to the listserv mailer is re-sent to
  everyone on the mailing list.

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More Groupware
ICQ (web site) ICQ Newsgroups Web Search
ICQ Web-Pager ICQ Friendship Pages
E-greeting
Gaming E-mail Internet Telephony External
Applications

• Multicast Backbone (MBONE)

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Network Models
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Network Model

• A method of describing and analyzing data
  communications networks, by breaking the entire
  set of communications functions into a series of
  layers, each of which can be defined separately.
• This allows vendors to develop software and
  hardware to provide the functions separately.

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Open Systems Interconnection (OSI)

• Developed by the International Organization for
  Standardization (ISO) in 1984
• The primary architectural model for intercomputer
  communications.
• A conceptual model composed of seven layers, each
  specifying particular network functions.
• Describes how information from a software
  application in one computer moves through a
  network medium to a software application in
  another computer.

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Why Study OSI?

• Still an excellent model for conceptualizing and
  understanding protocol architectures
• Key points
• Modular
• Hierarchical
• Boundaries between layersinterfaces

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ISOs OSI Model

• OSI has 7 layers
• Application layer
• Presentation layer
• Session layer
• Transport layer
• Network layer
• Data link layer
• Physical layer

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OSI Lower Layers

• Physical Layer 1
• Responsible for transmission of bits
• Always implemented through hardware
• Encompasses mechanical, electrical, and
  functional interfaces
• e.g. RS-232
• Data Link Layer 2
• Responsible for error-free, reliable transmission
  of data
• Flow control, error correction
• e.g. Ethernet
• Network Layer 3
• Responsible for routing of messages through
  network
• Concerned with type of switching used (circuit v.
  packet)
• Handles routing between networks, as well as
  through packet-switching networks

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OSI Upper Layers

• Transport
• Isolates messages from lower and upper layers
• Breaks down message size
• Monitors quality of communications channel
• Selects most efficient communication service
  necessary for a given transmission
• Session
• Establishes logical connections between systems
• Manages log-ons, password exchange, log-offs
• Terminates connection at end of session
• Presentation
• Provides format and code conversion services
• Example File conversion from ASCII to EBDIC
• Application
• Provides access to network for end-user
• Users capabilities are determined by what items
  are available on this layer
• Logic needed to support various applications
• Each type of application requires different
  software on this layer

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Application Viewpoint of a Network

• Distributed data communications involves three
  primary components
• Networks
• Computers
• Applications
• Three corresponding layers
• Network access layer
• Transport layer
• Application layer

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TCP/IP

• Transmission control Protocol/Internet Protocol
• Developed by DARPA
• No official protocol standard
• Can identify five layers
• Application
• Host-to-Host (transport)
• Internet
• Network Access
• Physical

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OSI Model
Internet Model
OSI Model
Application layer http, telnet, snmp, smtp,
nfs, ftp
TCP, UDP
Internet layer IP layer
IPv4, IPv6
Layer 3
Data Link Layer
(HDLC)
Network access layer
Layer 2
Physical layer
Layer 1
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Sender
Receiver
Application Layer
Application Layer
HTTP
Request
HTTP
Request
Transport Layer
Transport Layer
HTTP
TCP
Request
HTTP
TCP
Request
Network Layer
Network Layer
HTTP
TCP
IP
Request
HTTP
TCP
IP
Request
Data Link Layer
Data Link Layer
HTTP
TCP
IP
Ethernet
Request
HTTP
TCP
IP
Ethernet
Request
Physical Layer
Physical Layer
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Distributed Data Processing
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Data Processing

• Centralized data processing
• Computer, data, control, staff and processing are
  centralized
• Distributed data processing (DDP)
• May include centralized center plus satellite
  facilities
• Involves distributed computer, data, and
  processing
• Greater flexibility in meeting individual needs
• More redundancy and more autonomy

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Reasons for DDP

• Need for new applications
• On large centralized systems, development can
  take years
• On small distributed systems, development can be
  component-based and very fast
• Need for short response time
• Centralized systems result in contention among
  users and processes
• Distributed systems provide dedicated resources

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Networking Implications

• Connectivity requirements
• What links between components are necessary?
• Availability requirements
• Percentage of time application or data is
  available to users
• Performance requirements
• Response time requirements

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Functions of Data Processing System

• The work done by any application program can be
  divided into four general functions
• data storage
• data access logic
• application logic
• presentation logic

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Network Architecture

• Students list link in course homepage

Student records
Web browser
Web Server
students.pl
Data Storage
Presentation Logic
Application Logic Data Access Logic
Geek (129.118.49.111)
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Servers

• A computers suitability to serve as the server
  or host for an online, real-time data
  communication network depends on both its own
  capabilities and the capabilities of other
  attached hardware.
• There are three typical types of hosts
• Mainframe computers
• Minicomputers
• Microcomputers

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Clients

• The client is the input/output hardware device at
  the users end of the communications circuit.
• There are four major categories of clients
• Terminals
• Microcomputers / workstations
• Network computers
• Special purpose terminals

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Network Architectures

• From a viewpoint of distributed application
  system, there are three fundamental network
  architectures
• Host-based networks the host computer performs
  virtually all of the work
• Client-based networks the client computer
  performs virtually all of the work
• Client-server networks the work is shared
  between the hosts and clients

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Host-Based Architectures
Host-Based Architectures
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Client-Based Architectures
Example Novell NetWare 3.12
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Client-Server Architectures

• More organizations today are moving to
  client-server architectures.
• Client-Server attempts to balance the processing
  between the client and the server by having both
  do some of the processing.

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Costs and Benefits of Client-Server
Architectures

• Client-server architectures are scaleable
• Client-server architectures can support many
  different types of clients and servers.
• Because no single host computer supports all the
  applications, the network is generally more
  reliable.

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Client-Server Architectures

• Client-server architectures also have some
  critical limitations, the most important of which
  is their complexity.
• Even updating the network with a new version of
  the software is more complicated too.
• Much of the debate between host- and
  client-server networks has centered on cost.
  Microcomputer hardware is more than 1000 times
  cheaper than mainframe hardware for the same
  amount of computing power.

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Middleware

• Client-server networks enable software and
  hardware from different vendors to be used
  together. Unfortunately, they have few
  standards. One solution is middleware, software
  that sits between the application software on
  both the client and the server.
• Middleware does two things
• It provides a standard way of communicating that
  can translate between software from different
  vendors.
• It manages the message transfer from clients to
  servers so that the clients need not know the
  specific server that contains the applications
  data.

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Middleware

• Examples of middleware
• OMG's CORBA (Common Object Request Broker
  Architecture)
• Open Groups DCE (Distributed Computing
  Environment)
• DCOM (Distributed Component Object Model)
• ODBC (Open Database Connectivity) and OLEDB
• JDBC (Java Database Connectivity)

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Two-tier, Three-tier, and N-tier Architectures
Two-tiered client-server architecture
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Web Architecture
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Two-tier, Three-tier, and N-tier Architectures
Three-tiered client-server architecture
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N-tier Architectures
N-tiered client-server architecture
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5-Tier Example

• IMWs Forum User Database Updating

SQL Server 7.0
NT/IIS
NT/IIS
BSD/Apache
NT Web Server
NT Web Server
Web Browser
FTP Server
Database Server
Member
Member
Forum
Chicago
Austin
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Thin Clients versus Fat Clients

• Another way of classifying client-server
  architectures is by examining how much of the
  application logic is placed on the client.
• A thin client places little or no logic on the
  client, and are easier to manage.
• A fat client places all or almost all of the
  application logic on the client.
• There is no direct relationship between thin/fat
  clients and 2-/3-/n-tiered architectures.

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Network Architecture
Thin client/server
Presentation Logic
Application Logic
Client/server
Middleware
Application Logic
Data Access Logic
Client-based
Data Storage
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Web Services
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Introduction

• Web
• Application to user communication across the
  internet.
• Web Services
• Application to application communication across
  the internet.
• Self-contained and modular applications.
• Can be described, published, located, and invoked
  over a network.
• Applications can be built by discovering and
  orchestrating network-available services.
• A Web Service is described using a formal XML
  notation called service description.

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Web Services Description and Standards

• Service Description
• Message Format
• Transport Protocol
• Location
• Encapsulates implementation details
• Key standards used to reach this new horizon
• Hyper Text Transport Protocol (HTTP)
• Extensible Markup Language (XML)
• Simple Object Access Protocol (SOAP)
• Web Services Description Language (WSDL)
• Universal Description, Discovery and Integration
  (UDDI)
• Business Process Execution Language for Web
  Services (BPEL4WS)

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Architecture Overview(Conceptual Web Services
Stack)
Service Flow
BPEL4WS
Service Discovery
Static? UDDI
Service Publication
Direct ? UDDI
Service Description
WSDL
XML-Based Messaging
SOAP
Network
HTTP, FTP, e-mail, MQ, IIOP, etc.
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Main players and standards

• Microsoft .NET
• SUN Open Net Environment (ONE)
• IBM Web Service Conceptual Architecture (WSCA)
• W3C Web Service Workshop
• Oracle Web Service Broker
• Hewlett-Packard Web Service Platform

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Web Services standards

• WSDL Web Services Description Language
  http//www.w3.org/TR/wsdl
• descriptions of Web Services
• UDDI Universal Discovery, Description
  Integration http//www.uddi.org/spec
  ification.html
• registries containing service descriptions
• SOAP Simple Object Access Protocol
  http//www.w3.org/TR/SOAP/
• transport protocol for communication between Web
  Services
• BPEL4WS
• http//xml.coverpages.org/bpel4ws.html
• Emerging standards WSRP, WSIA, WSXL.

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Simple Object Access Protocol (SOAP)

• A way for a program running in one kind of OS to
  communicate with a program in the same or another
  kind of OS by using HTTP and XML as the
  mechanisms for information exchange.
• SOAP specifies exactly how to encode an HTTP
  header and an XML file so that a program in one
  computer can call a program in another computer
  and pass it information. It also specifies how
  the called program can return a response.

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IBM Web Services model
Service provider

WSDL SOAP
WSDL UDDI
Publish
Bind
Service requestor
Service registry
Find
WSDL UDDI
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Service Registries

• UDDI Web Service standard
• Global public registry
• Private registries
• JISC Information Environment registry
• Grid Service registry
• Service type
• Service instance
• Functionality
• Registries are dynamic services
• Implement searching across multiple registries
• New Web Services compliant products ?

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Web Service Model

• The Web Services architecture describes three
  roles
• Service provider
• Service requester
• Service registry
• It describes three basic operations
• Publish
• Find
• Bind.
• It also has two artifacts
• Service
• Service description

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Web Service Model
Service Description
Service
Web Services roles, operations and artifacts
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Web Services Model

• The web services development lifecycle
• Build
• Deploy
• Run
• Manage
• To perform three operations (publish, find, and
  bind) in an interoperable manner, there must be a
  Web services stack that embraces standards at
  each level.
• The IBM Web Services Stack is examined.