MIS 3360

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MIS 3360

• Chapter 11 Networked Applications

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Simple Terminal-Host System
All Processing is Done on the Host Slow Response
Time Monochrome Text Little Graphics
Direct Wire Connection
Dumb Terminal
Telephone Network
Modem
Modem
Host
Dumb Terminal
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Client/Server Computing
File Server Program Access

• Only useful for small programs (e-mail, word
  processing, etc.)
• Because clients do not get very large

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Mainframe vs. Client/Server Architecture
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(No Transcript)
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Three-Tier Architecture
Web Server
Presentation
Payment
User/Admin
Content
Business Logic
Modules
Data
Database
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Electronic Commerce Functions
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Electronic Commerce Functions

• Webserver Functionality, Plus
• E-Commerce functionality
• Online catalog
• Shopping cart
• Checkout, including payment
• Customer resource management
• Links to External Systems
• Credit card number checking
• Bank settlement

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Electronic Commerce Functions

• E-Commerce functionality
• Links to internal systems
• Accounting
• Pricing
• Warehousing (Product Availability)
• Shipment
• Etc.

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Application Server (3-Tier Architecture
Client PC with Browser
Web- server
Application Server
4. DB Server Query and Response
Mainframe
5. External Query/ Response
Database Server
Database Sever Interactions (4, 5)
Application program interfaces (API) Both
internal and external database hosts
Server of External Company
Figure 11-11
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E-Commerce Security
Subnet for Internal Hosts (Little or No
Access From Outside)
DMZ Subnet (Easy Access from Outside)
Customer
Ethernet Switch
DMZ Subnet for Externally-Facing Servers
E-Commerce Server
Accounting Server
Marketing Client
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Ordinary Webservice versus Web Service
Ordinary Webservice
HTTP Request
Browser
Webserver Application
HTTP Response
Webserver
Client PC
HTML Document
Ordinary webservice was created to download
documents
Figure 11-13
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Ordinary Webservice versus Web Service
Web Service
HTTP Request
SOAP- Capable Browser
HTTP Response
Web Service -- Interface Properties Methods
Just enough web services to survive
Webserver
Client PC
SOAP Message Using XML Syntax
Web services are objects (programs) Clients send
them commands and data Web services send back
results
Figure 11-13
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Simple SOAP Request and Response

• SOAP Request Message

HTTP Request Header pointing to program lt?xml
version1.0gt ltBODYgt ltQuotePrice
xmlnsQuoteInterfacegt
ltPartNumgtQA78dlt/PartNumgt
ltQuantitygt47lt/Quantitygt
ltShippingTypegtRushlt/ShippingTypegt
lt/QuotePricegt lt/BODYgt
Note xmlns specifies an XML namespace for the
object
Figure 11-14
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Simple SOAP Request and Response

• SOAP Response Message

HTTP Response Header lt?xml version1.0gt ltBODYgt
ltQuotePrice xmlnsQuoteInterfacegt
ltPricegt750.33lt/Pricegt
lt/QuotePricegt lt/BODYgt
Figure 11-14
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Peer-to-Peer Computing
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Traditional Client/Server Application
Disadvantages Network Overload at
Server Underused Client Power Central Control
Advantage Central Control
Server Does Heavy Processing Work
Figure 11-16
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Simple Peer-to-Peer (P2P) Application
Request
Response
Benefits End User Freedom No Network Bottleneck
at Serve Uses Client Capacity Better
Problems Transient Presence of Clients Transient
Client IP Addresses Security (No Central Control)
Figure 11-17
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P2P Applications

• Direct service, although some P2P systems use
  facilitating servers for some of the work

Peer
Peer
Peer
Peer
Peer
Peer
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Gnutella Pure P2P with Viral Networking
Gnutella Client (ABC)
2. Init or Search Message
3. Init or Search Message
1. Init or Search Message
3. Init or Search Message
Gnutella Client (DEF)
2. Init orSearch Message
3. Init or Search Message
Gnutella Client (Carol)
4. P2P File Download HTTP Request-Response Cycle
Gnutella Client (XYZ)
Gnutella Client (GHI)
Figure 11-18
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Use of Servers in Instant Messaging
Pure P2P IM
Ongoing Communication
Client PC A
Client PC B
In pure P2P IM, there are no servers The clients
communicate directly Finding each other can be
difficult because of DHCP
Figure 11-20
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Use of Servers in Instant Messaging
Use of a Presence Server
2. Presence Information
1. Presence Information
3. Ongoing Communication
Client PC C
Client PC D
Clients register with presence servers Presence
servers notify other clients as
appropriate Clients use this information to
communicate directly
Figure 11-20
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Use of Servers in Instant Messaging
Use of a Relay Server
All Communication Goes through the Relay Server
Presence Information
Client PC E
Client PC F
Relay servers route all IM messages. This permits
security filtering and other services. It limits
privacy because the relay server sees everything.
Figure 11-20
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Perspective on Application Architectures

• Driven primarily by the evolution of client
  processing power
• Terminal-Host Client processing power was
  uneconomical
• Client/Server Client PCs could handle some of
  the load
• P2P Clients have rich power to do most things
• Grid computing