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Chapter 3 :
Distributed Data Processing
Business Data Communications,
4e
Centralized Data Processing
Centralized computers, processing, data,
control, support
What are the advantages?
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Economies of scale (equipment and personnel)
Lack of duplication
Ease in enforcing standards, security
How is data communications implemented?
Examples? Holiday Inn
Figure 3.1 (p.42)
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Distributed Data Processing
Computers are dispersed throughout
organization
Allows greater flexibility in meeting individual
needs
More redundancy
More autonomy
How is data communications implemented?
Examples? J.P. Morgan (Figure 3.2, p.44)
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Why is DDP Increasing?
Dramatically reduced workstation costs
Improved user interfaces and desktop
power
Better end-user programming
Ability to share data across multiple
servers
DDP Pros & Cons
There are no “one-size-fits-all” solutions
Key issues
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How
How
How
How
does
does
does
does
it
it
it
it
affect
affect
affect
affect
end-users?
management?
productivity?
bottom-line?
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Benefits of DDP
Responsiveness
Availability
Correspondence to
Org. Patterns
Resource Sharing
Incremental Growth
Increased User
Involvement &
Control
End-user
Productivity
Distance & location
independence
Privacy and security
Vendor
independence
Flexibility
Drawbacks of DDP
More difficulty test & failure diagnosis
More components and dependence on
communication means more points of failure
Incompatibility of components
Incompatibility of data
More complex management & control
Difficulty controlling information resources
Suboptimal procurement
Duplication of effort
Reasons for DDP
Need for new applications
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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
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Centralized systems result in contention among users
and processes
Distributed systems provide dedicated resources
The DP “Pendulum”
Centralized systems (mainframes, etc)
Distributed systems (PCs)
Networked systems
Client-Server computing
Client/Server Architecture
Combines advantages of distributed and
centralized computing
Cost-effective, achieves economies of
scale
Flexible, scalable approach
Intranets
Uses Internet-based standards &
TCP/IP
Content is accessible only to internal
users
A specialized form of client/server
architecture
Extranets
Similar to intranet, but provides access
to controlled number of outside users
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Vendors/suppliers
Customers
Virtual Private Networks - VPN
Use encryption and authentication
Provide secure connection to LAN via
insecure network (Internet)
Cheaper than real private networks,
but less reliable
Encryption performed by firewall or
routers
VPN (Virtual Private Network)
VPN技術
穿隧技術 (Tunneling)
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IPSec (IP Security)
PPTP (Point-to-Point Tunneling Protocol)
L2TP (Layer 2 Tunneling Protocol)
加解密技術 (Encryption/Decryption)
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Private/Public/Hybrid Key Encryption
密鑰管理 (Key Management)
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SKIP (Simple Key Management for IP)
IKE (ISAKMP/Oakley)
使用者與設備身份認證技術 (Authentication)
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Username/Password + Token Number
X.509 Certificate by Certificate Authority (CA)
What is distributed?
Distributed applications
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One application dispersed among systems
One application replicated on systems
Different applications on different systems
Distributed data
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centralized database (not distributed data)
replicated database
partitioned database
Distributed applications
Horizontal partitioning
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Different applications on different systems
One application replicated on systems
Example: Office automation
Vertical partitioning
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One application dispersed among systems
Example: Retail chain POS, inventory,
analysis
Distributed data
Centralized database
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Pro: No duplication of data
Con: Contention for access
Replicated database
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Pro: No contention
Con: High storage and data reorg/update costs
Partitioned database
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Pro: No duplication, limited contention
Con: Ad hoc reports more difficult to assemble
Networking Implications
Connectivity requirements
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What links between components are
necessary?
Availability requirements
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Percentage of time application or data is
available to users
Performance requirements
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Response time requirements