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Internet Applications and Distributed Data Processing. Topic 2. Outline. Internet Applications The Internet Internet applications Network Models Distributed Data Processing Network Architectures Network Configurations. Internet Applications. Internet Applications.

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outline
Outline
  • Internet Applications
    • The Internet
    • Internet applications
  • Network Models
  • Distributed Data Processing
    • Network Architectures
    • Network Configurations
internet applications1
Internet Applications

There are four important Internet application software tools

  • the Web
  • electronic mail (e-mail)
  • FTP
  • Telnet

Less important applications: WAIS, gopher

world wide web
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.

CERN’s first Web browser was written in 1990, but it was 1991 before it was available on the Internet for other organizations to use.

world wide web1
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 university’s National Center for Supercomputing Applications (NCSA)

In 1994, Andreessen and some colleagues left NCSA to form Netscape.

how the web works
How the Web Works

Server computer with

Web Server

software

HTTP Request

Client computer with

Web Browser

software

HTTP Response

how the web works1
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)
how the web works2
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 17:35:46 GMT

User-Agent: Mozilla/3.0

From: adennis@uga.cc.uga.edu

Referer: http://tcbworks.cba.uga.edu/~adennis/home.htm

]- Request Line

]- Date

]- Web browser (this is Netscape)

Request Header

]- User’s 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

slide11

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 17:35:46 GMT

Server: NCSA/1.3

Location: http:// tcbworks.cba.uga.edu/~adennis/res.htm

Content-type: text/html

<html>

<head>

<title>Business Data Communications and Networking Web Resources </title>

</head>

<body>

<H2>Resources on the Web </H2>

<P>This section contains links to other resources

on the WEB that pertain to the field of data communications

and networking </P>

</body>

</html>

]- Date

]- Web server

Response

Header

]- URL

]- Type of file

Response

Body

internet search engines
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.

e mail standards
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.
e mail standards1
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.
how the smtp e mail works
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

how web based e mail works
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

HTTP response

SMTP packet

Internet

SMTP packet

Server computer with

mail server

software

HTTP request

Client computer with

Web browser

LAN

IMAP or

SMTP packet

HTTP response

IMAP packet

Server computer with

Web server

software

how the instant messaging works
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

e mail directories
E-mail Directories
  • Before you can send an e-mail message, you must know the receiver’s 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.
other network applications
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.
listserv
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. Anymessage sent to the listserv mailer is re-sent to everyone on the mailing list.

more groupware
More Groupware
  • Multicast Backbone (MBONE)

ICQ (web site)

ICQ Newsgroups

Web Search

ICQ Web-Pager

ICQ Friendship Pages

E-greeting

Gaming

E-mail

Internet Telephony

External Applications

network model
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.

open systems interconnection osi
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.
why study osi
Why Study OSI?
  • Still an excellent model for conceptualizing and understanding protocol architectures
  • Key points:
    • Modular
    • Hierarchical
    • Boundaries between layers=interfaces
iso s osi model
ISO’s OSI Model

OSI has 7 layers:

  • Application layer
  • Presentation layer
  • Session layer
  • Transport layer
  • Network layer
  • Data link layer
  • Physical layer
osi lower layers
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
osi upper layers
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
    • User’s 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
application viewpoint of a network
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
tcp ip
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
osi model
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

slide34

Sender

Receiver

Application

Layer

Application

Layer

HTTP

Request

HTTP

Request

Transport

Layer

Transport

Layer

TCP

HTTP

Request

TCP

HTTP

Request

Network

Layer

Network

Layer

IP

TCP

HTTP

Request

IP

TCP

HTTP

Request

Data Link

Layer

Data Link

Layer

Ethernet

IP

TCP

HTTP

Request

Ethernet

IP

TCP

HTTP

Request

Physical

Layer

Physical

Layer

data processing
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
reasons for ddp
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
networking implications
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
functions of data processing system
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
network architecture
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)

servers
Servers

A computer’s 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
clients
Clients

The client is the input/output hardware device at the user’s end of the communications circuit.

There are four major categories of clients:

  • Terminals
  • Microcomputers / workstations
  • Network computers
  • Special purpose terminals
network architectures
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
host based architectures
Host-Based Architectures

Host-Based Architectures

client based architectures
Client-Based Architectures

Example: Novell NetWare 3.12

client server architectures
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.

costs and benefits of client server architectures
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.
client server architectures1
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.
middleware
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 application’s data.
middleware1
Middleware

Examples of middleware:

  • OMG's CORBA (Common Object Request Broker Architecture)
  • Open Group’s DCE (Distributed Computing Environment)
  • DCOM (Distributed Component Object Model)
  • ODBC (Open Database Connectivity) and OLEDB
  • JDBC (Java Database Connectivity)
two tier three tier and n tier architectures
Two-tier, Three-tier, and N-tier Architectures

Two-tiered client-server architecture

two tier three tier and n tier architectures1
Two-tier, Three-tier, and N-tier Architectures

Three-tiered client-server architecture

n tier architectures
N-tier Architectures

N-tiered client-server architecture

5 tier example
5-Tier Example

IMW’s Forum User Database Updating

SQL Server 7.0

NT/IIS

BSD/Apache

NT/IIS

Web

Browser

NT Web

Server

FTP

Server

NT Web

Server

Database

Server

Member

Forum

Member

Chicago

Austin

thin clients versus fat clients
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.
network architecture1
Network Architecture

Thin

client/server

Presentation Logic

Application Logic

Client/server

Middleware

Application Logic

Data Access Logic

Client-based

Data Storage

introduction
Introduction
  • Web
    • Application to usercommunication across the internet.
  • Web Services
    • Application to applicationcommunicationacross 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.
web services description and standards
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)
architecture overview conceptual web services stack

Security

Management

Quality of Services

Interoperable base

Web Services stack

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.

main players and standards
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
web services standards
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/specification.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…….
simple object access protocol soap
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.
ibm web services model
IBM Web Services model

Service

provider

WSDL

SOAP

WSDL

UDDI

Publish

Bind

Service

requestor

Service

registry

Find

WSDL UDDI

service registries
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 ?
web service model
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
web service model1

Service

Description

Service

Requester

Service

Registry

Service

Provider

Find

Publish

WSDL, UDDI

WSDL, UDDI

Bind

Web Service Model

Service

Description

Service

Web Services roles, operations and artifacts

web services model
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.