1. Middleware
IS 8040 Data Comm and
Networking
Dr. Hoganson
Middleware
• What is middleware?
• A software interface glue that resides between the operating system (or
network operating system) and the application in distributed
client/server systems.
Client
Application
Middle-
ware
NOS
Physical
NW Layers
Server
Application
Middle-
ware
NOS
Physical
NW Layers

2. Middleware
IS 8040 Data Comm and
Networking
Dr. Hoganson
• Vertical Integration:
– Between layers in each stack
– Each layer interfaces with its neighbors
– Between application and middleware is the API: Application
Programming Interface
• Horizontal Integration
– Between equivalent layers located at client and server
– Middleware achieves horizontal integration between client and
server middleware

3. Middleware
IS 8040 Data Comm and
Networking
Dr. Hoganson
Interfaces
• Middleware must be compatible with and interface with the network
operating system
• Middleware must be able to interface with the API
• Compatibility issues

4. Middleware
IS 8040 Data Comm and
Networking
Dr. Hoganson
Middleware Tiers
Server
Application
Middle-
ware B
NOS
Physical
NW Layers
Server
Application
Middle-
ware A
NOS
Physical
NW Layers
Client
Application
Middle
-ware
A
NOS
Physical
NW Layers
Middle
-ware
B
2 Tier Middleware Architecture

5. Middleware
IS 8040 Data Comm and
Networking
Dr. Hoganson
Middleware Tiers
Server
Application
Middle-
ware A
NOS
Physical
NW Layers
Client
Application
Client
Middleware
NOS
Physical
NW Layers
Application
Middle-
ware A
NOS
Physical
NW Layers
Middle-
ware B
n-Tier Middleware Architecture (three tiers)
Server
Application
Middle-
ware B
NOS
Physical
NW Layers
ClientM
iddle-
ware

6. Middleware
IS 8040 Data Comm and
Networking
Dr. Hoganson
Simple Example of n-Tiers
Server
Application
Middle-
ware A
SQL
NOS
Physical
NW Layers
Client
Application
Client
Middleware
Browser
NOS
Physical
NW Layers
Application
SQL
server
NOS
Physical
NW Layers
VB
n-Tier Middleware Architecture (3-Tier)
Server
Application
Middle-
ware B
VB
NOS
Physical
NW Layers
ClientM
iddle-
ware
HTML

7. Middleware
IS 8040 Data Comm and
Networking
Dr. Hoganson
N-Tier architecture
• Simplifies client software
– Development
– Configuration & Maintenance – fewer products & protocols
– (true cost of computing includes ALL personnel support costs)
• Fewer client resources consumed (less memory and processing power)
• De-couples the development of the server systems from the client
interface
• Facilitates platform independence