CORBA: An Overview

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CORBA An Overview

• Mojtaba Hosseini

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Outline

• Motivation
• Introduction to CORBA
• Evolution of CORBA
• CORBA Core
• Interoperability and internetworking
• Conclusion

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Motivation

• Applications working under different environments
• Operating System
• Programming Language
• Distributed applications such as IP telephony
  must communicate
• Over different network protocols
• How can these applications work together?

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Interoperability Problem
Mac OS
Windows OS
Smalltalk IP Telephony Application
Java IP Telephony Application
?
?
Network architectures and standards (SIP, ISDN,
IP, ATM, etc)
Linux OS
C IP Telephony Application
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Introduction to CORBA

• Common Object Request Broker Architecture
• Interface Definition Language (IDL), Object model
  and Object Request Broker (ORB) as key elements
• Main idea provide standardized interfaces for
  transparent requesting/providing of services

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Main Idea Behind CORBA

• Client requests service without knowing where
  provider is and in what environment (programming
  language, operating system)
• Object provides service without knowing about the
  clients environment or location

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Evolution of CORBA
Real-time Fault Tolerance
Horizontal, Vertical Facilities
Interoperability Networking
IDL, Object Model, ORB
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CORBA Object Model
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Schedule

• CORBA IDL
• Dynamic Invocation
• ORB Interface
• Object Adaptor
• Interoperability
• New features

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IDL

• IDL used to define service interface
• IDL is defined just like any programming
  language
• defines keywords (e.g. void)
• literals (e.g. character literal x)
• Identifiers (e.g. int numb)
• restrictions on these (e.g. identifier cant
  start with a number)

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IDL Grammar

• IDL also defines a grammar
• IDL can then be mapped into executable
  programming languages such as Java/C

12
Schedule

• CORBA IDL
• Dynamic Invocation
• ORB Interface
• Object Adaptor
• Interoperability
• New features

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Dynamic Invocation and Skeleton

• IDL stub/skeleton not the only way to
  request/provide services
• What if we dont know about the interface at
  compile time? But we know what service we want to
  request?
• Need Dynamic Invocation

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Dynamic Invocation

• Client defines signature of service name,
  parameters, return value, context
• ORB gives this to the object and object
  determines which method to invoke
• Useful for providing different interfaces for the
  same service

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Dynamic Invocation Example

• Three telephone call charging policies
• Depending on originating/terminating location
• Depending on terminating location only
• Constant billing

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Schedule

• CORBA IDL
• Dynamic Invocation
• ORB Interface
• Object Adaptor
• Interoperability
• New features

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ORB Interface

• Provides common interfaces such as
• ORB operations shutdown, initialize
• Object operation are two objects equivalent?
• Policy operation deny/allow services
• Policy Management overriding policies
• ORB exceptions no implementation available

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Schedule

• CORBA IDL
• Dynamic Invocation
• ORB Interface
• Object Adaptor
• Interoperability
• New features

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Portable Object Adaptor

• Allow for multiple object implementations to
  exist on server side (e.g. multiple billing
  services for several companies)

VendorA Billing Service
VendorB Billing Service
Choose billing Service based on policy
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Schedule

• CORBA IDL
• Dynamic Invocation
• ORB Interface
• Object Adaptor
• Interoperability
• New features

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GIOP/IIOP

• Multiple vendors implementing ORBs
• A need for ORBs to interface with one another in
  a standard way General Inter-ORB Protocol
• GIOP generic protocol, no implementation
• IIOP (Internet Inter-ORB Protocol) is the TCP/IP
  implementation of GIOP

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CORBA and Interoperability
Mac OS
Windows OS
Smalltalk IP Telephony Application
Java IP Telephony Application
ORB
ORB
GIOP
GIOP
Network architectures and standards (SIP, ISDN,
IP, ATM, etc)
Linux OS
ORB
C IP Telephony Application
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Schedule

• CORBA IDL
• Dynamic Invocation
• ORB Interface
• Object Adaptor
• Interoperability
• New features

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More Recent CORBA features

• Domains such as Transportation, Health Care,
  Finance, etc. developed IDL interface common in
  their domain
• CORBA standardized these for the domains
• More recent CORBA versions include
• Real-time capabilities
• Fault-tolerance

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Conclusion

• There exist different environments in which
  telephony applications operate
• There is a need for these applications to be
  interoperable
• CORBA provides the standard way of doing so