www.5starnotes.com MC9295 Parallel and Distributed Computing
m
UNIT -1
co
PART-A 1. What is DCE?
te
2. What are the three distributed computing models based on DCE?
s.
DCE (Distributed Computing Environment) is an architecture defined by the Open Software Foundation (OSF) to provide an Open Systems platform to address the challenges of distributed computing. It is being ported to all major IBM® and many non-IBM environments. Note that all current DCE implementations use TCP/IP rather than SNA as their communication protocol.
3.What is mean by RPC?
ar
no
Client/server A way of organizing a distributed application Remote procedure call A way of communicating between parts of a distributed application Shared files A way of handling data in a distributed system, based on a personal computer file access model.
w. 5s t
Remote procedure call (RPC).One way of implementing communications between a client and a server of a distributed application is to use the procedure call model. In this model, the client makes what looks like a procedure call, and waits for a reply from the server. The procedure call is translated into network communications by the underlying RPC mechanism. The server receives a request and executes the procedure, returning the results to the client. 4.what are the Application of Distributed computing?
ww
Examples of commercial application :
Database Management System Distributed computing using mobile agents Local intranet Internet (World Wide Web) JAVA Remote Method Invocation (RMI)
5.Advantages of Distributed environment? Economics:-
www.5starnotes.com
www.5starnotes.com Computers harnessed together give a better price/performance ratio than mainframes.
Inherent distribution of applications:-
co
A distributed system may have more total computing power than a mainframe.
m
Speed:-
s.
Some applications are inherently distributed. E.g., an ATM-banking application. Reliability:-
no
1. Explain in detail about DCE remote procedure calls
te
If one machine crashes, the system as a whole can still survive if you have multiple server machines and multiple storage devices (redundancy). WWW.5starnotes.com PART-B
ar
This section gives an overview of how CICS cooperates with the OS/390 Unix Systems Services DCE Base Services MVS/ESA and OS/390 Unix Systems Services DCE Application Support MVS/ESA CICS Feature products to enable a CICS program to act as a DCE server.
w. 5s t
Refer to the following books for more information about the OS/390 Unix Systems Services DCE Base Services MVS/ESA product:
DCE: Understanding the Concepts Introducing the z/OS Distributed Computing Environment z/OS Distributed Computing Environment: Application Development Guide, for guidance information about developing the client code and using the Unix System Services DCE MVS/ESA base services. z/OS Distributed Computing Environment: Application Development Reference, for reference information about application programming interfaces (APIs).
ww
Refer to the following books for more information about the OS/390 Unix Systems Services DCE Application Support MVS/ESA CICS Feature:
OS/390 DCE Application Support Programming Guide, for information about how to install CICS remote procedure call server programs. z/OS Distributed Computing Environment: Application Support Configuration and Administration Guide, for information about the administration tasks that complement the programming tasks.
2. What you need for DCE RPC to a CICS server?
www.5starnotes.com
www.5starnotes.com This support requires the following products:
m
no
te
co
Connectivity through TCP/IP protocols to the client workstation, and to the DCE directory and security servers. This normally means a TCP/IP network, though for some partner platforms it may be possible to use an SNA network with ANYNET support at both ends to transport TCP/IP protocols using SNA transmission protocols. IBM® TCP/IP for MVS™, Version 3 Release 1 or later, to present a TCP/IP interface to the DCE software, even if you are using an SNA network and ANYNET software. OS/390® Unix Systems Services Distributed Computing Environment Base Services MVS/ESA, Version 5 Release 1 or later. OS/390 Unix Systems Services Distributed Computing Environment Application Support MVS/ESA CICS® Feature, Version 1 Release 1 or later.
s.
3. Write a note on Distributed Computing Using Mobile Agents Mobile agents can be wandering around in a network using free resources for their own computations.
ww
w. 5s t
ar
www.5starnotes.com
Local Intranet
ar
no
te
s.
co
m
www.5starnotes.com
ww
w. 5s t
A portion of Internet that is separately administered & supports internal sharing of resources (file/storage systems and printers) is called local intranet.
www.5starnotes.com
www.5starnotes.com 4.Explain in detail about JAVA RMI?
Object variant of remote procedure call Adds naming compared with RPC (Remote Procedure Call)
w. 5s t
ar
no
te
s.
Restricted to Java environments
co
m
Embedded in language Java:-
ww
Java Remote Method Invocation (RMI), which is a simple and powerful network object transport mechanism, provides a way for a Java program on one machine to communicate with objects residing in different address spaces. Some Java parallel computing environments use RMI for communication, such as JavaParty, discussed in next section. It is also the foundation of Jini technology--discussed on section 2.1.5. RMI is an implementation of the distributed object programming model, comparable with CORBA, but simpler, and specialized to the Java language. An overview of the RMI architecture is shown in Figure 2.1. Goals A primary goal for the RMI designers was to allow programmers to develop distributed Java programs with the same syntax and semantics used for non-distributed programs. To do this, they
www.5starnotes.com
www.5starnotes.com
m
had to carefully map how Java classes and objects work in a single Java Virtual Machine1 (JVM) to a new model of how classes and objects would work in a distributed (multiple JVM) computing environment.
co
Java RMI Architecture
s.
The design goal for the RMI architecture was to create a Java distributed object model that integrates naturally into the Java programming language and the local object model. RMI architects have succeeded; creating a system that extends the safety and robustness of the Java architecture to the distributed computing world.
w. 5s t
ar
no
te
Important parts of the RMI architecture are the stub class, the object serialization, and the serverside Run-time System. The stub class implements the remote interface and is responsible for marshaling and unmarshaling the data and managing the network connection to a server. An instance of the stub class is needed on each client. Local method invocations on the stub class will be made whenever a client invokes a method on a remote object. Java has a general mechanism for converting objects into streams of bytes that can later be read back into an arbitrary JVM. This mechanism, called object serialization, is an essential functionality needed by Java's RMI implementation. It provides a standardized way to encode all the information into a byte stream suitable for streaming to some type of network or to a file-system. In order to provide the functionality, an object must implement the Serializable interface. The server-side run-time system is responsible for listening for invocation requests on a suitable IP port, and dispatching them to the proper, remote object on the server. Since RMI is designed for Web based client-server applications over slow network, it is not clear it is suitable for high performance distributed computing environments with low latency and high bandwidth. A better serialization would be needed, since Java's current object serialization often takes at least 25% and up to 50% of the time [50] needed for a remote invocation.
ww
Stubs: •
Stub is a piece of code emulating a called function , It is a temporary called program.It functions similarly like sub modules when called by the main module.
•
A piece of code that simulates the activity of missing component.
•
Stubs are simulations of the sub-code that otherwise is very difficult to execute in the test code.
•
Stub is a simple routine that takes the place of the real routine.
Skeletons: •
The role of the stubs is to marshal and unmarshal the messages that are sent and received on the client or the server side .
www.5starnotes.com
www.5starnotes.com Economics:-
Speed:-
s.
A distributed system may have more total computing power than a mainframe.
co
Computers harnessed together give a better price/performance ratio than mainframes.
m
5. Merit and Demerit of distributed environment?
Inherent distribution of applications:-
Some applications are inherently distributed. E.g., an ATM-banking application.
te
Reliability:-
no
If one machine crashes, the system as a whole can still survive if you have multiple server machines and multiple storage devices (redundancy). Extensibility and Incremental Growth:-
Distributed custodianship:-
ar
Possible to gradually scale up (in terms of processing power and functionality) by adding more sources (both hardware and software). This can be done without disruption to the rest of the system.
w. 5s t
The National Spatial Data Infrastructure (NSDI) calls for a system of partnerships to produce a future national framework for data as a patchwork quilt of information collected at different scales and produced and maintained by different governments and agencies. NSDI will require novel arrangements for framework management, area integration, and data distribution. This research will examine the basic feasibility and likely effects of such distributed custodianship in the context of distributed computing architectures, and will determine the institutional structures that must evolve to support such custodianship. Data integration:-
ww
This research will contribute to the integration of geographic information and GISs into the mainstream of future libraries, which are likely to have full digital capacity. The digital libraries of the future will offer services for manipulating and processing data as well as for simple searches and retrieval. Missed opportunities:-
www.5starnotes.com
www.5starnotes.com
co
m
By anticipating the impact that a rapidly advancing technology will have on GISs, this research will allow the GIS community to take better advantage of the opportunities that the technology offers.
Demerit:
s.
Complexity :-
Lack of experience in designing, and implementing a distributed system. E.g. which platform (hardware and OS) to use, which language to use etc.
te
Network problem:-
no
If the network underlying a distributed system saturates or goes down, then the distributed system will be effectively disabled thus negating most of the advantages of the distributed system. Security:-
ww
w. 5s t
ar
Security is a major hazard since easy access to data means easy access to secret data as well.
www.5starnotes.com
