RMI (Remote Method Invocation)

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Firewall Issue in RMI

Firewall issues

  1. Firewalls are inevitably encountered in any network, that has to operate beyond the sheltering confines of an Intranet.
  2. They block all the network traffic with certain exceptions defined in the rule-set.
  3. Since RMI opens a dynamic socket connection, between client and server to facilitate communication, the JRMP traffic is blocked by most protocols.
  4. On top of TCP/IP RMI uses a wire level protocol – Java Remote Method Protocol (JRMP).
  5. To get across a firewall, RMI makes use of HTTP tunneling by encapsulating RMI calls, within an HTTP post.

CLIENT BEHIND FIREWALL

  1. In the above scenario, when the transport layer tries to establish a connection with the server, it is blocked by the firewall.
  2. When this happens, the RMI transport layer automatically retries by encapsulating the JRMP call data within an HTTP POST request. The HTTP POST header for the call is in the form:
  3. http://hostname:port
  4. If a client is behind a firewall, it is important that you also set the system property http.proxyHost appropriately.
  5. Since almost all firewalls recognize the HTTP protocol, the specified proxy server should be able to forward the call directly to the port on which the remote server is listening on the outside.
  6. Once the HTTP-encapsulated JRMP data is received at the server, it is automatically decoded and dispatched by the RMI transport layer.
  7. The reply is then sent back to client as HTTP-encapsulated data.

CLIENT & SERVER BEHIND FIREWALL

  1. In this case, the RMI transport layer uses one additional level of indirection. This is because the client can no longer send the HTTP-encapsulated JRMP calls to arbitrary ports as the server is also behind a firewall. Instead, the RMI transport layer places JRMP call inside the HTTP packets and send those packets to port 80 of the server. The HTTP POST header is now in the form
  2. http://hostname:80/cgi-bin/java-rmi?forward=<port&gt;
  3. This causes the execution of the CGI script, java-rmi.cgi, which in turn invokes a local JVM, unbundles the HTTP packet, and forwards the call to the server process on the designated port.
  4. RMI JRMP-based replies from the server are sent back as HTTP REPLY packets to the originating client port where RMI again unbundles the information and sends it to the appropriate RMI stub.
  5. Of course, for this to work, the java-rmi.cgi script, which is included within the standard JDK 1.1 or Java 2 platform distribution, must be preconfigured with the path of the Java interpreter and located within the web server’s cgi-bin directory.
  6. It is also equally important for the RMI server to specify the host’s fully-qualified domain name via a system property upon startup to avoid any DNS resolution problems, as:
  7.  java.rmi.server.hostname=host.domain.com.

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Linux

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1.    What is Linux?

Linux is, in simplest terms, an operating system. It is the software on a computer that enables applications and the computer operator to access the devices on the computer to perform desired functions. The operating system (OS) relays instructions from an application to, for instance, the computer’s processor. The processor performs the instructed task, then sends the results back to the application via the operating system.

But something sets Linux apart from these operating systems. The Linux operating system represented a $25 billion ecosystem in 2008. Since its inception in 1991, Linux has grown to become a force in computing, powering everything from the New York Stock Exchange to mobile phones to supercomputers to consumer devices.

As an open operating system, Linux is developed collaboratively, meaning no one company is solely responsible for its development or ongoing support. Companies participating in the Linux economy share research and development costs with their partners and competitors. This spreading of development burden amongst individuals and companies has resulted in a large and efficient ecosystem and unheralded software innovation.

Over 1,000 developers, from at least 100 different companies, contribute to every kernel release. In the past two years alone, over 3,200 developers from 200 companies have contributed to the kernel–which is just one small piece of a Linux distribution.

This article will explore the various components of the Linux operating system, how they are created and work together, the communities of Linux, and Linux’s incredible impact on the IT ecosystem.

  1. Where is Linux?

One of the most noted properties of Linux is where it can be used. Windows and OS X are predominantly found on personal computing devices such as desktop and laptop computers. Other operating systems, such as Symbian, are found on small devices such as phones and PDAs, while mainframes and supercomputers found in major academic and corporate labs use specialized operating systems such as AS/400 and the Cray OS.

Linux, which began its existence as a server OS and Has become useful as a desktop OS, can also be used on all of these devices. ‚ÄúFrom wristwatches to supercomputers,‚Äù is the popular description of Linux’ capabilities.

An abbreviated list of some of the popular electronic devices Linux is used on today includes:

These are just the most recent examples of Linux-based devices available to consumers worldwide. This actual number of items that use Linux numbers in the thousands. The Linux Foundation is building a centralized database that will list all currently offered Linux-based products, as well as archive those devices that pioneered Linux-based electronics.

Linux_1
Linux_1

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Maths formula

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  1. COMPOUND INTEREST

M = P( 1 + i )n

M is the final amount including the principal.

P is the principal amount.

i is the rate of interest per year.

n is the number of years invested.

Applying the Formula

Let’s say that I have $1000.00 to invest for 3 years at rate of 5% compound interest.

M = 1000 (1 + 0.05)3 = $1157.62.

You can see that my $1000.00 is worth $1157.62.

Area and Perimeter of a Triangle, Rectangle, Parallelogram, Trapezoid and Circle

Area and Perimeter of a Triangle, Rectangle, Parallelogram, Trapezoid and Circle
Area and Perimeter of a Triangle, Rectangle, Parallelogram, Trapezoid and Circle
Area and Perimeter of a Triangle, Rectangle, Parallelogram, Trapezoid and Circle
Area and Perimeter of a Triangle, Rectangle, Parallelogram, Trapezoid and Circle

Surface Area and Perimeter of a Triangle

  Surface Area and Perimeter of a Triangle

Surface Area and Perimeter of a Triangle

Career in Embedded System

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Career in Embedded System

Embedded Systems are becoming more and more pervasive, touching virtually all aspects of daily life. From mobile phones to automobiles, industrial equipment, to high end medical devices, home appliances etc. Embedded software today sits at the intersection of all the technologies. The growth of different industry sectors like automotive, telecommunications, aerospace, energy, industrial units, biomedical equipment, consumer goods is highly contributed by the development in the field of Embedded Systems. According to a survey by Frost and Sullivan, an analyst firm, the embedded systems opportunity is expected to touch $360 billion ( in terms of the devices) and $36 billion in terms of the semiconductors by 2015. Another survey by NASSCOM and McKinsey predicts that the jobs in embedded space will increase ten-fold from the current 60,000 professionals to over 6 lakh people by 2015. Companies like TCS, Wipro, L&T, TATA Elexsi, Infosys, Zensar, Tech Mahindra, Patni, VOLVO, NIIT Tech, KPIT Cummins, Airbus etc. are investing heavily in their embedded systems operations in India. With that expectation, in the near future embedded computing will overtake traditional computing and that there may be more engineers working on embedded systems and related services , then on traditional IT. Experts say what IT was in 90’s is where embedded systems stands now and is ready to explode. The future is bright for India with it being pegged to be the next embedded systems hub in the world. A recent study by NASSCOM talks about the Indian Embedded Ecosystem. This ecosystem consists of all the stakeholders in embedded domain namely, the education institutions, end user industries and entrepreneurial organizations. NASSCOM suggests that there is a need to nurture this ecosystem that would catalyze innovation in the Indian embedded industry.

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Embedded systems and technologies

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The future is bright for embedded systems and technologies!!

The tech world is going through unprecedented changes in the last few quarters. Apple and Samsung have taken the mobile phone market leadership to a different level where both of them have surged forward from their nearest rivals, in terms of innovation, technology and the revenue/profits earned in this business. We now see that Software, Operating System players like Microsoft and Google have entered the HW market through their own branded products. The message is loud and clear—the companies are looking at increased business from the consumer and the actions that the consumer carries out in the internet; they are out to influence the consumer side devices as well as the server/network side applications in order to maximise the business. All of these changes are having a huge impact on the traditional eco systems in the mobile, handheld, consumer markets. Only time will tell if the integrated strategies played out by Apple is the way to go for the consumer electronics leaders of the world, though there is an apparent shift in that direction. All of these changes are fuelling tremendous growth in the embedded markets. Some of the trends that we see in the embedded system design markets are as follows:

Increased use of multi-core processor platforms: Traditional embedded systems design principles ensured processor and design simplicity in order to meet the stringent needs of cost, reliability, thermal performance, etc. So the use of multi-core processors was not very common. Of late new process and power conservation technologies are driving the use of multi-core processors in embedded system design without impacting the traditional principles. Enhancements in processor design is looking not only at the increased clock speed, but considers increased efficiency, lower power consumptions and integrated graphic performance.

Connectivity is driving security needs in the devices:

The convergence of devices features and technologies are happening faster than anyone’s imagination these days and the need for connectivity is driving the device designs. All this is adding a security nightmare to preserve personal and professional information from hostile attacks. The embedded system components (processor, operating system, applications) need to have better security features in them in order to tackle these challenges.

Demand for Video processing:

The enhanced processing power in the devices are driving the need to have better video processing for personal and professional data transfers and there is an increasing trend in devices that have video capability being designed. Innovative application use cases are built in to take advantage of the social networking and other converged platforms to share video across devices. Irrespective of the global economic turbulence, there would be continued investments in providing more innovative and efficient solutions coming up in the embedded domain to cater to these trends. In order to be a winner in the embedded market, the companies and individuals need to constantly develop and innovate on new ideas, approaches that can provide efficient, fast, low power, cost effective solutions to the consumers. The above trends of increased video data, security needs and use of complex processors would demand a new level of expertise in providing these solutions.

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FUNCTIONAL DEPENDENCY OF THE DATA

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FUNCTIONAL DEPENDENCY OF THE DATA

  Functional dependency of data means that the attribute within a given entity are fully dependent on the entire primary key of the entity-no more, no less.

The implication is that each attribute has a one-to-one relationship with its primary key. For each instance of a primary key, there is one set of applicable values; for each attribute, there is only one primary key that properly gives it its identity.

For example, in the customer entity, names, DOB all belong to the primary key of CustomerID.

If the columns with each table contain attributes with proper functional dependency, then the simplest way to make a change to any column is to rely on the functional dependency.

Each change will be applied to one attribute in one place.

If customer changes name, then the customer row and change the name.

If the new customer address is used as the mailing address, go to address role and change it there-one place. Functional dependency is not irrelevant in analytical models.

When you define a level, you define a relationship between the level key attributes and the other attributes in the level (default attribute and related attributes). The relationship indicates that the level key attributes can be used together to determine the other attributes in the level. DB2 Data Warehouse Edition documents the relationship between the level’s attributes by defining functional dependencies between the attributes. The relationships, defined by functional dependencies, can be used to perform intelligent optimization of your data.

If a functional dependency exists between a level key attribute and the level’s related attributes, the Optimization Advisor wizard can include the level key attribute without the related attributes in the summary table. Queries that are interested in the level’s related attributes can still be routed to the summary table because the DB2 optimizer joins the summary table with the dimension table when the query is issued to create the final result set.

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SCOPE OF THE DATA WAREHOUSE

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DATA WAREHOUSE OPTIONS

   There are many ways to develop data warehouse as there are organization and  number of key factors that need to be considered:

  • SCOPE OF THE DATA WAREHOUSE
  • DATA REDUNDANCY
  • TYPE OF END – USER

        i.            SCOPE OF THE DATA WAREHOUSE

The scope of a data warehouse may be as broad as all the informational data for the entire enterprise from the beginning of time, or it may be as narrow as a personal data warehouse for a single manager for a single year. There is nothing that makes one of these more of a data warehouse than another.

     ii.            DATA REDUNDANCY

There are essentially three levels of data redundancy that enterprises should think about when considering their data warehouse options:

a)    “virtual” or “point – to point” data warehouses

b)    Central data warehouses

c)     Distributed data warehouses

A)    “VIRTUAL” OR “POINT TO POINT” DATA WAREHOUSES

A virtual or point to point data warehousing strategy means that end users are allowed to get at operational databases directly, using whatever tools are enabled to the “ data access network” this approach provides the ultimate in flexibility as well as the minimum amount of redundant data must be loaded and maintained.

 

B) CENTRAL DATA WAREHOUSES

A central data warehouses may contain records for any specific period of time and usually, contains information from multiple operational systems.

Central data warehouse are real. The data stored here is accessible from one place and must be loaded and maintained on a regular basis. Normally, data warehouses are built around advanced RDBMs or some form of multidimensional informational database server.

C)    DISTRIBUTED DATA WAREHOUSES

Distributed Data warehouses are those in which certain components are distributed across a number of different physical databases.

 

   iii.            TYPE OF END – USER

There are different ways to organize a data warehouse, it is also important to note that there is an increasingly wide range of end – users too. They can broadly be categorized into three;

Executives and managers

Power users (business and financial analysts, engineers)

Support users (clerical, administrative)

Each of these has its own set of requirements for data, access, flexibility and ease of use.

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