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SRI RAMAKRISHNA INSTITUTE OF TECHNOLOGY

DEPARTMENT OF INFORMATION TECHNOLOGY

UNIT II- DISTRIBUTED ENTERPRISE COMMUNICATIONS ENABLING

TWO MARKS

1. What is the use of distributed system?

The distributed enterprise systems problem can involve issues such as

➢ scalability

➢ wide-area geographical distribution

➢ heterogeneous platform interfacing.

2. List the issues in Distributed Systems

➢ Reliable Transport Communications

➢ Language Dependencies

➢ Platform Dependencies

➢ Client/Server Interfacing

➢ Object Activation

➢ Object Name Binding Creation

➢ Deletion, Copying and Moving, Event Handling

➢ Persistence Security.

3. Represent the network client model

[pic]

4. Define STUB and SKELETON

A stub for a remote object is the client’s local representative or proxy for the remote object. The stub hides the serialization of parameters and the network level communication in order to present a simple invocation mechanism.

Skeleton is responsible for dispatching the call to the actual remote object implementation.

5. Represent the network Server model

[pic]

6. What are the actions performed when stub method is invoked

➢ Initilization of the connection with the remote object

➢ Marshalling the parameters to the remote methods

➢ Waiting for the result of the method invocation

➢ Unmarshalling the return value or exception returned

➢ Returning the value to the caller

7. What are the various stages of Distributed System?

➢ Dumb Terminal & Mainframe Computing

➢ Desktop Computing

➢ LAN Computing

➢ Internet Computing

➢ World Wide Web Computing

➢ N-Tier Enterprise Computing

8. What are the different types of Network Client Models?

➢ TCP/IP Clients

➢ HTTP Clients

➢ CORBA Clients

➢ RMI Clients

➢ DCOM Clients

9. Define RMI

The Remote Method Invocation is used for remote communication between Java Application’s and components, both of which must be written in Java programming language.

10. What are the set of tools that are used to implement RMI application?

➢ RMI Compiler(rmic):

➢ IDL-to-Java Compiler(idlj):

➢ RMI Registry(rmiregistry)

➢ RMI/IIOP Naming Service(tnameserv):

➢ RMI Activation Daemon(rmid):

11. What are the packages used to implement RMI application?

➢ java.rmi

➢ java.rmi.server

➢ java.rmi.registry

➢ java.rmi.activation

➢ java.rmi.dgc

➢ javax.rmi

12. Draw the architecture of RMI.

[pic]

13. List the RMI development process.

➢ Create an remote interface

➢ Create an remote class implementation

➢ Generate the RMI stubs and skeleton (rmic)

➢ Implement both Client and Server

➢ Register the RMI (rmiregistry)

➢ Compile and run Server and Client Program

14. Define CORBA ?

The Common Object Request Broker Architecture (CORBA) is independence of hardware platform, programming language & operating system and it is used for remote communication. CORBA works with IDL Interfaces.

15. List the responsibility of ORB.

➢ Data Marshalling

➢ Object location management

➢ Delivering request to objects

➢ Returning output values back to the client

16. Mention about IDL Interface.

Interfaces are language-independent descriptions of interfaces to CORBA server objects. IDL Interface is defined in CORBA IDL module. Module is similar to java package and it is a name space for interface and declaration.

17. What are steps involved in CORBA Development process?

➢ Define IDL Interface

➢ Compile IDL Interface

➢ Implement CORBA Client

➢ Implement CORBA Server

➢ Implement CORBA Server registrar

➢ Register interfaces with an interface repository

➢ Run both client and server

18. Draw the architecture for CORBA.

[pic]

19. What are the major difference between IDL and Java?

|IDL |JAVA |

|1. module MyApplication |package My application |

|2. interface MyApplication |public interface MyApplication |

|3. string mymethod() |String mymethod() |

|4. oneway void shutdown() |void Shutdown() |

20. How is ORB specification done in CORBA?

The ORB is really just a set of CORBA specifications. The term ORB actually refers to a collection of software libraries used either by CORBA clients to access distributed services or by CORBA servers to make their services distributed. The CORBA server is a distributed object offering up some of its method calls for remote access. CORBA clients are those objects that make remote method calls on CORBA servers.

21. What is the use of marshaling and unmarshaling the data stream?

Client stubs handle packing (that is, marshaling) method-call parameters and unpacking (that is, unmarshaling) method-call return values to and from CORBA communications protocol message formats. Stubs also handle identifying which method on a particular CORBA server is being invoked by packing such identifying information into the marshaled data stream to be sent to the server

22. What is the use of interface repositories in CORBA?

Interface Repositories are small databases used in some ORB implementations to hold the metadata descriptions of CORBA server interfaces in a machine-readable version of the CORBA Interface Definition Language. Interface Repositories have a standard API callable by CORBA clients and are also used by DII implementations.

23. What are the two different protocols for CORBA based application?

➢ General Inter-Orb Protocol (GIOP)

➢ Internet Inter-Orb Protocol (IIOP)

GIOP defines a means for mapping marshaled IDL data into a common way to represent data over the wire and a set of message formats encapsulating the request and reply semantics of distributed calls. IIOP maps GIOP message data into TCP/IP connection behavior.

24. Differentiate RMI and CORBA.

|RMI |CORBA |

|1. RMI Interface are defined in JAVA |CORBA Interfaces are defined in IDL(Interface definition|

| |language) |

|2. RMI was designed for a single language where all |CORBA is language independence |

|objects are written in JAVA | |

|3. RMI objects are garbage collected automatically |CORBA objects are not garbage collected |

25. Specify the header format present in JRMP

- Java Remote Method Protocol contains a message header and one or more messages.

❖ 4 Bytes ( ASCII Character

❖ 2 Bytes ( Protocol Version Number

❖ 1 Byte ( Sub protocol identifier

26. Specify the header format present in GIOP

.

The header format simply consists of these elements:

• Four bytes of characters always of the form: GIOP.

• Two bytes for GIOP protocol version numbers.

• A Boolean value indicating the byte order of the message (used in GIOP v1.0 messages only).

• A byte of bit flags used to indicate things like byte ordering, as well as whether this message is fragmented into multiple subsequent messages (used in GIOP v1.1 and v1.2 messages).

• A single byte message type identifier.

• A byte specifies the size of the message following the header.

27. What are the services provided by the CORBA facilities

CORBA facilities represent higher-level and more application-specific services and frameworks used in building distributed systems than is the case with CORBA services.

CORBA facilities can provide component services such as email, printing, and global positioning information. CORBA facilities are further broken down into two categories: Horizontal Common Facilities and Vertical Market Facilities.

28. How can be COM defined as component interface model

COM can defined as a component interface model for Windows-based applications. COM clients can make use of such components by interfacing with COM libraries to obtain component handles and then making calls to such interfaces, which in turn map to local procedure calls. Such local calls map to a call on the actual COM component service. Although COM interfaces were defined at a binary level in the past, COM now has evolved to enable the definition of components using higher-level language interfaces.

29. What are the steps involved in DCOM development process?

➢ Define your IDL interface

➢ Generate your GUIDs (guidgen)

➢ Generate a type library(midl)

➢ Generate Java bindings(jactivex)

➢ Implement the DCOM server interfaces(jvc)

➢ Register the DCOM server (javareg)

➢ Implement the DCOM client (jvc)

➢ Register the DCOM client-side interfaces (javareg)

➢ Run the Client (jview)

30. What is the difference between Bind and Rebind methods

The server registrar can use the static Naming.bind() or Naming.rebind() method to register an instantiated server object implementation with a name in the RMI registry.

The difference between bind() and rebind() is that bind() throws an AlreadyBoundException if an object of that name is registered with the RMI registry, whereas rebind() replaces any objects already bound with that name. The Naming class actually uses a java.rmi.registry.Registry interface to an object that talks with theassociated rmiregistry instance running.

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