1. Lecture 5 Client-server Computing
5.1 Two Host Architecture
5.2 Three-Tier Client-Server Architecture
5.3 Application Examples
5.5 Open Issue: Beyond Client-Server Computing
Reading: Chapter 5
Adapted from David G. Messerschmitt

2. Client
host
Client
host
Server
host

3. Part of the rationale Specialization: Sharing:
Clients specialize in user interface
Servers specialize in managing data and application logic
Sharing:
Many clients can be supported by few servers
Often data and logic are shared among applications and users

4. Copyright 1999, University of California
Lecture 5 Client-server computing (24 slides)
“I want to
collaborate
with my
colleague”
“I want to access
some information”
Client
Server
Peer-to-peer
Client/server

5. Distinctions Client-server Peer-to-peer Asymmetric relationship
Client predominately makes requests, server makes replies
Peer-to-peer
Symmetric relationship
No server but only desktop computers

6. Email application Server Client Client
client sends message to server
Later, recipient’s client retrieves message from server
Message is stored on POP server

7. Chat application Server Client Client
Chat server aggregates typing from all users and sends to all clients
Other user’s clients display aggregated typing from chat server
Chat clients send user’s typing to server

8. Copyright 1999, University of California
Lecture 5 Client-server computing (24 slides)
5.2 Three-tier client-server architecture
Local-area network
Application
logic
Presentation
Note: many clients per
application server, several
application servers per data server
Shared
data

9. Copyright 1999, University of California
Lecture 5 Client-server computing (24 slides)
Client
Host architecture
Web
browser
Web
server
Common
gateway
interchange
Application logic
Databases and DBMS
Application partition

10. Departments
Enterprise-to-enterprise
Commerce
Consumer
Enterprise

11. Figure 3.2, p. 64 software4u.com Customers Customer-service department
Technical-support
department
Consumer
Enterprise

12. Customer care Consumer application Enterprise application Web browser
Web server
Web server
Web server
Customer care
Customer logic
Agent logic
Technician logic
Customer
audit
Software
documentation
Problem
knowledge
base
Databases

13. Customers
Agents
Technicians
Customer logic
Agent logic
Technician logic
Databases
Accounts
Products
Orders

14. books4u.com Financial institution Book distribution centers Customers
Consumer
Enterprise
Inter-enterprise

15. Book merchant Consumer e-commerce Inter-enterprise e-commerce Acquirer
Web
browser
Web server
Book merchant
Customer logic
Fulfillment logic
Outside links
Customers
Merchandise
Orders
Databases
Acquirer
bank
Book
distributors

16. Clients Acquirer bank Customer logic Databases Book distributors
Fulfillment logic
Databases
Book
distributors
Merchandise
Orders
Customers

17. Information providers
Customers
Stock market
stocks4u.com
Consumer
Enterprise
Inter-enterprise

18. Stock trader Consumer e-commerce Inter-enterprise e-commerce Web
browser
Web server
Stock trader
Customer logic
Trading logic
Outside links
Accounts
Products
Orders
Databases
Information
providers
Financial
markets

19. Clients
Information
providers
Customer logic
Trading logic
Databases
Financial
markets
Accounts
Products
Orders

20. Financial institution
Customers
flowers4u.com
Local florists
Consumer
Enterprise
Inter-enterprise

21. Florist delivery Consumer e-commerce Inter-enterprise e-commerce Web
browser
Push server
Web server
Push client
Florist delivery
Customer logic
Fulfillment logic
Outside link
Accounts
Products
Orders
Databases
Acquirer
bank

22. Customers Florists Customer logic Fulfillment logic Acquirer bank
Databases
Accounts
Products
Orders

23. 5.5 Shortcomings of client/server
Copyright 1999, University of California
Lecture 5 Client-server computing (24 slides)
5.5 Shortcomings of client/server
Departmental solution
Proliferates non-interoperable technologies and applications
Hardwired applications lose flexibility
What are some goals and likely characteristics of future enterprise architectures?
Major goal: flexibility to meet new business opportunities and new organizational structures
More tiers to logically decouple roles
Away from stovepipe: horizontal as well as vertical structure

24. Web Surfing and Homework #5
Homework:
E5.1 (one example)
E5.5 (a)(C)(e)