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Network Load Balancing Services

Network Load Balancing Services

Network Load Balancing Services (NLBS) is a proprietary Microsoft implementation of clustering and load balancing that is intended to provide high availability and high reliability, as well as high scalability. NLBS is intended for applications with relatively small data sets that rarely change (one example would be web pages), and do not have long-running-in-memory states. These types of applications are called stateless applications, and typically include Web, File Transfer Protocol (FTP), and virtual private networking (VPN) servers. Every client request to a stateless application is a separate transaction, so it is possible to distribute the requests among multiple servers to balance the load.

Microsoft

Microsoft Corporation (, ) is the world's largest software company, with 2005 global annual sales of 40 billion US dollars and more than 55,000 employees in 85 countries and regions. The company's headquarters are in Redmond, Washington, USA. Microsoft develops, manufactures, licenses, and supports a wide range of software products for computing devices. Its most popular products are the Microsoft Windows operating system and the Microsoft Office suite of productivity software, each of which has achieved near ubiquity in the desktop computer market. Microsoft has footholds in other markets, with assets such as the MSNBC cable television network, the MSN Internet portal, and the Microsoft Encarta computer encyclopedia. The company also markets home entertainment products, such as the Xbox and WebTV. "Micro-Soft" (short for microcomputer software) was founded in Albuquerque, New Mexico in 1975 by Bill Gates and Paul Allen, to develop and sell BASIC interpreters for the Altair 8800. After the market saw a flood of IBM PC clones in the mid-1980s, Microsoft used its new position, which it gained in part due to a contract from IBM, to dominate the home computer operating system market with its MS-DOS operating system. The company later released an initial public offering (IPO) in the stock market, which netted several of its employees millions of dollars due to the ensuing rise of the stock price. The price of the stock continued its rise steadily into the early 2000s. In Microsoft Windows, the company was selling what would become the most widely used operating system in the world, which was originally an add-on for their DOS operating system; Microsoft continued to push into multiple markets, such as computer hardware and television. In addition, Microsoft has historically given customer support over Usenet newsgroups and the World Wide Web, and awards Microsoft MVP status to volunteers who are deemed helpful in assisting the company's customers. With what is generally described as a developer-centric business culture, Microsoft has become widely known for some of its internal codes of conduct for its employees. One example is the "eat your own dogfood" mantra, which describes the practice of using pre-release products inside the company to test them in an environment geared towards the real world. Microsoft has also become notorious for its business practices—the U.S. Justice Department, among others, has sued Microsoft for antitrust violations and software bundling. In addition, Microsoft has been criticized for the security of its software. Despite this, Microsoft has won several awards, such as the "1993 Most Innovative Company Operating in the U.S." by Fortune Magazine. The company is on the Fortune 500 list of companies as of 2005. Microsoft opened its first research center outside the US at the Cambridge Science Park, UK. It currently has research centers around the world.

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History

:See also: History of Microsoft Windows. First conceived in 1975 by Bill Gates and Paul Allen, Microsoft has evolved through several stages throughout its history. By 1985, the company was selling the Microsoft Windows operating system and MS-DOS, and had collaborated with IBM to produce OS/2 Warp. By 1992, Microsoft had released an IPO in the stock market and discontinued OS/2 development to focus directly on Windows. By 1995, Windows was the most widely used graphical operating system in the world, and with the introduction of Windows 95, the company became a more consumer-driven company. Microsoft would proceed to enter other business markets, such as publishing and video games, would be sued more than once by the U.S. Justice Department and other governments and companies, and would continue to dominate the operating system market.

1975–84: the founding of Micro-soft

video game.
Top row: Steve Wood (left), Bob Wallace, Jim Lane. Middle row: Bob O'Rear, Bob Greenberg, Marc McDonald, Gordon Letwin. Bottom row: Bill Gates, Andrea Lewis, Marla Wood, Paul Allen.]] Days after reading the January 1 1975, issue of Popular Electronics that demonstrated the Altair 8800, Bill Gates called the creators of the new microcomputer, MITS (Micro Instrumentation and Telemetry Systems), to inform them that he and others had developed a version of the programming language BASIC for the platform. Allen flew to MITS to unveil the new BASIC system. Allen had never handled an Altair, since Gates had carried out all of the product development; however, the demonstration was successful and resulted in a deal with MITS to buy the rights to Allen's and Gates' BASIC for the Altair platform. Having identified a valuable opportunity, Gates left Harvard University to pursue the market and eventually founded "Micro-soft" in Albuquerque, New Mexico. The name Microsoft, without the hyphen, was first used in a letter from Gates to Allen on November 29, 1975, and in November 26, 1976 the name became a registered trademark. The company's first international office was founded on November 1, 1978, in Japan, entitled "ASCII Microsoft". On January 1, 1979, the company moved from Albuquerque to a new home in Bellevue, Washington. Steve Ballmer joined the company on June 11, 1980, and would later succeed Bill Gates as CEO. The company restructured on June 25 1981, to become an incorporated business in its home state of Washington (with a further change of its name to "Microsoft, Inc."). As part of the restructuring, Bill Gates became president of the company and Chairman of the Board, and Paul Allen became Executive Vice President. Microsoft's first operating system was Xenix, released in 1980 and later sold to Santa Cruz Operation. However, the source of the real success for the company was the DOS operating system. On August 12, 1981, after negotiations with Digital Research failed, IBM awarded a contract to Microsoft to provide a version of the CP/M operating system, which was set to be used in the upcoming IBM Personal Computer (PC). However, Microsoft did not have an operating system at the time, so it purchased a CP/M clone called QDOS (Quick and Dirty Operating System) from Tim Paterson of Seattle Computer Products for $50,000, which Microsoft renamed to PC-DOS. Due to potential copyright infringement problems with CP/M, IBM marketed both CP/M and PC-DOS for $250 and $40, respectively, with PC-DOS eventually becoming the standard because of its lower price. Around 1983, in collaboration with numerous companies, Microsoft created a home computer system, MSX, which contained its own version of the DOS operating system, entitled MSX-DOS; this became relatively popular in Japan and Europe. Later, after Compaq successfully cloned the IBM BIOS, the market saw a flood of IBM PC clones. Microsoft was quick to use its position to dominate the home computer operating system market. Microsoft began licensing its operating system for use on non-IBM PC clones, and called this version of the operating system MS-DOS (short for Microsoft Disk Operating System). By marketing MS-DOS aggressively to manufacturers of IBM-PC clones, Microsoft rose from a small player to one of the major software vendors in the home computer industry. Starting on May 2, 1983, with the "Microsoft Mouse", Microsoft entered markets such as computer hardware. This expansion included Microsoft Press, a book publishing division, on November 10 the same year, which debuted with two titles: "Exploring the IBM PC Home Computer" by Peter Norton, and "The Apple Macintosh Book" by Cary Lu.

1985–91: the rise and fall of OS/2

Cary Lu The Republic of Ireland became home to Microsoft's first international production facility in 1985, and on November 20 Microsoft released its first retail version of Microsoft Windows, originally a graphical extension for its MS-DOS operating system. In August, Microsoft and IBM partnered in the development of a different operating system called OS/2. OS/2 was marketed in connection with a new hardware design proprietary to IBM, the PS/2. Shortly afterwards on February 16, 1986, Microsoft relocated to Redmond, Washington. Around one month later, on March 13, the company went public with an IPO, raising $61 million at $21.00 per share. By the end of the trading day, the price had risen to $28.00. In 1987, Microsoft eventually released their first version of OS/2 to OEMs. Continuing its trend of rebranding products from other companies, Microsoft announced SQL Server on January 13, 1988, a relational database management system for companies that was based on technology licensed from Sybase. In 1989, Microsoft announced at Comdex that the 1991 release of Windows 3.0 would be the last version of Windows. Over the next few years, Microsoft continued to issue statements indicating that OS/2 was the future of computing. On May 16, 1991, Bill Gates announced to Microsoft employees that the OS/2 partnership was over, and that Microsoft would henceforth focus its platform efforts on Windows and the Windows NT kernel. Some people, especially developers who had ignored Windows and committed most of their resources to OS/2, were taken by surprise, and accused Microsoft of deception. The Windows changeover was frequently referred to in the industry as "the head-fake". In the ensuing years, the popularity of OS/2 declined, and Windows quickly became the favored PC platform. 1991 also marked the founding of Microsoft Research, an organization in Microsoft for researching computer science subjects, and Microsoft Visual Basic, a popular development product for companies and individuals.

1992–95: domination of the corporate market

Microsoft Visual Basic During the transition from MS-DOS to Windows, the success of Microsoft's product Microsoft Office allowed the company to gain ground on application-software competitors, such as WordPerfect and Lotus 1-2-3. Some allege that Microsoft used its inside knowledge of the DOS and Windows kernels and of undocumented Application Programming Interface features to make Office perform better than its competitors, but internal sources at Microsoft later revealed that the Office team did not have access to the Windows source code at the time, and relied on reverse engineering. Eventually, Microsoft Office became the dominant business suite, with a market share far exceeding that of its competitors. In March 1992, Microsoft released Windows 3.1 along with its first promotional campaign on TV; the software sold over three million copies in its first two months on the market. In October, Windows for Workgroups 3.1 was released with integrated networking capabilities such as peer-to-peer file and printing sharing. In November, Microsoft released the first version of their popular database software Microsoft Access. By 1993, Windows had become the most widely used GUI operating system in the world. Fortune Magazine named Microsoft as the "1993 Most Innovative Company Operating in the U.S.". The year also marked the end of a five-year legal case brought by Apple, dubbed Apple Computer, Inc. v. Microsoft Corp., in which the ruling was in Microsoft's favor. That same year, Microsoft released Windows for Workgroups 3.11, a new version of the consumer line of Windows, and Windows NT 3.1, a server-based operating system with a similar user interface to consumer versions of the operating system, but with an entirely different kernel. As part of its strategy to broaden its business, Microsoft released Microsoft Encarta in 1994, the first encyclopedia designed to run on a computer. Microsoft also created the Microsoft Plus product support program for its customers, a service that offered cost savings on Microsoft products. The name of that program was later used for several expansion packs for Windows. The company changed its slogan to "Where do you want to go today?" in that year, as part of an attempt to appeal to nontechnical audiences in a US$ 100 million advertising campaign, which some critics regarded as uninspired. Dreamworks SKG and Microsoft formed a new company, Dreamworks Interactive, to produce interactive and multimedia entertainment properties in 1995. In March, Microsoft released Microsoft Bob, a Windows 3.1 program manager replacement, which is widely considered Microsoft's most unsuccessful product; its unpopularity became the source of many jokes. Up until 1995, Microsoft was a business-oriented company. However, in August 1995, it released a new version of its flagship software, Microsoft Windows 95, with a completely new user interface, including a novel start button; more than a million copies of Microsoft Windows 95 were sold in the first four days after its release. The new version of Windows was the start of a major transition towards a consumer-oriented company. In September, the Chinese government chose Windows to be the operating system of choice in that country, and entered into an agreement with the Company to standardize a Chinese version of the operating system. Microsoft also released the Microsoft Sidewinder 3D Pro joystick in an attempt to further expand its profile in the computer hardware market.

1995–99: foray into the Internet and other venues

computer hardware In the mid-90s, Microsoft began to expand its product line into computer networking and the World Wide Web. On August 24, 1995, it launched a major online service, MSN (Microsoft Network), as a direct competitor to AOL. MSN became an umbrella service for Microsoft's online services, using Microsoft Passport as a universal login system for all of its websites. The company continued to branch out into new markets in 1996, starting with a joint venture with NBC to create a new 24/7 cable news station, MSNBC. The station was launched on July 16 to compete with similar news outlets—in particular, CNN; in the same year, Microsoft launched Slate, an online magazine edited by Michael Kinsley, which offered political and social commentary along with the cartoon Doonesbury. In an attempt to extend its reach in the consumer market, the Company acquired WebTV, which enabled consumers to access the Internet from their televisions. Microsoft entered the palm computing market in November with Windows CE 1.0, a new built-from-scratch version of their flagship operating system, specifically designed to run on low-memory, low-performance machines, such as handhelds and other palm-sized computers. 1996 saw the release of Windows NT 4.0, which brought the Windows 95 GUI and Windows NT kernel together. While Microsoft largely failed to participate in the rise of the Internet in the early 1990s, some of the key technologies in which the company had invested to enter the Internet market started to pay off by the mid-90s. One of the most prominent of these was ActiveX, an application programming interface built on the Microsoft Component Object Model (COM); this enabled Microsoft and others to embed controls in many programming languages, including the company's own scripting languages, such as JScript and VBScript. ActiveX included frameworks for documents and server solutions. The company also released the Microsoft SQL Server 6.5, which had built-in support for internet applications. Later in 1997, Microsoft Office 97 as well as Internet Explorer 4.0 were released, marking the beginning of the takeover of the browser market from rival Netscape, and by agreement with Apple, Internet Explorer was bundled with the Apple Macintosh operating system as well as Windows. Windows CE 2.0, the handheld version of Windows, was released this year, which included a host of bug fixes and new features designed to make it more appealing to corporate customers. In October, the Justice Department filed a motion in the Federal District Court in which they stated that Microsoft had violated an agreement signed in 1994, and asked the court to stop the bundling of Internet Explorer with Windows. In 1998, Microsoft released an update to the consumer version of Windows, Windows 98. Windows 98 came with Internet Explorer 4.0 SP1 (which had Windows Desktop Update bundled), and included new features from Windows 95 OSR 2.x including the FAT32 file system, and new features specifically for Windows 98, such as support for multiple displays. Microsoft also launched its Indian headquarters that year, which would eventually become the company's second largest after its U.S. headquarters. Steve Ballmer was appointed president of Microsoft, and Bill Gates remained as Chair and CEO. Later in 1999, Microsoft Office 2000 was released, along with Internet Explorer 5.0.

2000–05: legal issues, XP, and .NET

Internet Explorer 5.0. The largest Microsoft campus outside the United States.]] On May 18, 1998, the U.S. Department of Justice and 20 U.S. states filed charges against Microsoft, stating that Microsoft illegally abused its monopoly power in its sales of Windows, in United States v. Microsoft. However, it was not until April 3, 2000 that a ruling was made that Microsoft had to be split into two companies. However, in June 2001, part of that ruling was overturned by a federal appeals court, and in September the Justice Department decided to seek a settlement with Microsoft instead of trying to split it up. While the trial was underway, on February 17, 2000 Microsoft released Windows 2000, which some consider a significant improvement over previous versions. It provided a similar OS stability to that of its Unix counterparts. Unlike previous consumer-level operating systems, Windows 2000 was built on the Windows NT kernel, rather than the DOS kernel as previous consumer versions of Windows had been. Windows 2000 also provided a DOS emulator that could run most old DOS applications from previous versions of Windows. During the trial, Bill Gates stepped down as CEO and Steve Ballmer became the new CEO, with Bill Gates remaining chairman and Chief Software Architect. In the same year, Microsoft released a new version of the consumer version of their flagship product, Windows Me, (Millennium Edition). Widely regarded as one of the most unstable operating systems Microsoft had ever produced, its main features were enhanced multimedia capabilities, such as an automated video editor. In June, the company released a new version of its hand-held operating system, Windows CE 3.0. The main change was the new programming APIs of the software. Previous versions of Windows CE supported only a small subset of the WinAPI, the main development library for windows, and with Version 3 of Windows CE, the operating system now supported nearly all of the core functionality of the WinAPI. In 2001, Microsoft released Windows XP, which brought the consumer and business lines of Windows together, combining the kernel of Windows 2000 with features of its consumer line of Windows, and enhancing the DOS emulation capabilities of the OS. Among the new features was an entirely new interface. However, it included the controversial Microsoft Product Activation, a part of that software that required people to register with Microsoft before using the product for the first time, and if they did not the product would cease to function. This would become a hallmark of the Company's other products, including Microsoft Office. Microsoft Product Activation In 2003, Microsoft launched the .NET initiative, along with new versions of some of its development products, such as Microsoft Visual Studio. The initiative has been an entirely new development API for Windows programming, and includes a new programming language, C#. Windows Server 2003 was launched, featuring enhanced administration capabilities, such as new user interfaces to server tools. In 2004, the Company released Windows XP Media Center Edition 2005, a version of Windows XP specifically designed for multimedia capabilities, and Windows XP Starter Edition, a version of Windows XP with a smaller feature set designed for entry-level consumers. In March 2004, the European Union brought legal action against Microsoft for antitrust violations. Eventually Microsoft was fined $613 million, ordered to divulge certain protocols to competitors, and to produce a version of Windows that did not include the Windows Media Player. Microsoft announced a new version of its MSN search service later in 2005, designed to compete with Google.

Product divisions

Microsoft sells a wide range of products, many of them developed internally, such as Microsoft BASIC and Microsoft Word. Others were acquired and rebranded by Microsoft:
- Microsoft Project, a project management package;
- Visio, a charting package;
- FoxPro, a database;
- Links, a golf game;
- Visual SourceSafe, a developer's tool;
- DoubleSpace, a compression tool;
- Virtual PC, software to emulate different version of Windows, which was acquired from Connectix; and
- MS-DOS itself, the basis for the company's success. Many of these products have undergone continual development by the Company. Internet Explorer is based on code licensed from Spyglass, Inc.; the initial development of the software was performed outside Redmond in Spyglass headquarters. In April 2002, Microsoft reorganized into seven core business groups—'each an independent financial entity—to delegate all responsibility and more closely track the performance of each unit. On September 20th, 2005, Microsoft announced a rationalization of its original seven business groups to three core divisions: the Windows Client, MSN and Server and Tool groups were merged into the Microsoft Platform Products & Services Division; the Information Worker and Microsoft Business Solutions groups were merged into the Microsoft Business Division; and the Mobile and Embedded Devices and Home and Entertainment groups were merged into the Microsoft Entertainment and Devices Division.

Microsoft Platform Products & Services Division

2005 This division produces Microsoft's flagship product, the Windows operating system. It has been produced in many versions, including Windows 3.1, Windows 95, Windows 98, Windows 2000, Windows XP and Windows Server 2003. Almost all IBM compatible personal computers designed for the consumer come with Windows preinstalled. The next planned version of Windows is Windows Vista (code-named Windows Longhorn). The online service MSN, the cable television station MSNBC, and the Microsoft online magazine Slate are all part of this division. Slate was later acquired by The Washington Post on December 21, 2004. At the end of 1997, Microsoft acquired Hotmail, the first and most popular webmail service, which it rebranded as "MSN Hotmail". Later in 1999 Microsoft introduced MSN Messenger, an instant messaging client, to compete with the popular AOL Instant Messenger. Microsoft Visual Studio is the company's set of programming tools and compilers. The software product is GUI-oriented and links easily with the Windows APIs, but must be specially configured if used with non-Microsoft libraries. The current version is Visual Studio .NET 2003, named after the .NET initiative, a Microsoft marketing initiative covering a number of technologies. Microsoft's definition of .NET continues to evolve. As of 2004, .NET aims to ease the development of Microsoft Windows-based applications that use the Internet, by deploying a new Microsoft communications system, Indigo. This will address some issues previously introduced by Microsoft's DLL design, which made it difficult to manage, install multiple versions of complex software packages on the same system (see DLL-hell), and provide a more consistent development platform for all Windows applications (see Common Language Infrastructure. In addition, the Company established a set of certification programs to recognize individuals who have expertise in its software and solutions. Similar to offerings from Cisco, Sun Microsystems, Novell, IBM, and Oracle Corporation, these tests are designed to identify a minimal set of proficiencies in a specific role; this includes developers ("Microsoft Certified Solution Developer"), system/network analysts ("Microsoft Certified Systems Engineer"), trainers ("Microsoft Certified Trainers") and administrators ("Microsoft Certified Systems Administrator"). Microsoft offers a suite of server software, entitled Windows Server System. Windows Server 2003, an operating system for network servers, is the core of the Windows Server System line. Another server product, Systems Management Server, is a collection of tools providing remote-control abilities, patch management, software distribution, and a hardware/software inventory. Other server products include:
- SQL Server, a relational database management system;
- Exchange Server, for certain business-oriented e-mail features;
- Small Business Server, for messaging and other small business-oriented features; and
- BizTalk Server, for employee integration assistance and other functions.

Microsoft Business Division

BizTalk Server The Microsoft Business Division produces Microsoft Office, which is the company's line of office software. The software product includes:
- Word, a word processor;
- Access, a personal relational database application;
- Excel, a spreadsheet program;
- Outlook, Windows-only groupware, frequently used with the Exchange server;
- PowerPoint, presentation software; and Microsoft FrontPage, a WYSIWYG HTML editor. With the release of Office 2003, a number of other products were brought under the Office banner, including Microsoft Visio, Microsoft Project, Microsoft MapPoint, Microsoft InfoPath, Microsoft Publisher and Microsoft OneNote. The division focuses on developing financial and business management software for companies. These products include products formerly produced by the Business Solutions Group, which was created in April 2001 with the acquisition of Great Plains. Subsequently, Navision was acquired to provide a similar entry into the European market, resulting in the planned release of Microsoft Navision 4.0 during the week of 18 October, 2004. The group markets Axapta and Solomon, catering to similar markets, which is scheduled to be combined with the Navision and Great Plains lines into a common platform called Microsoft Dynamics.

Microsoft Entertainment and Devices Division

Microsoft Dynamics Microsoft has attempted to expand the Windows brand into many other markets, with products such as Windows CE for PDAs and its "Windows-powered" Smartphone products. Microsoft initially entered the mobile market through Windows CE for handheld devices, which today has developed into Windows Mobile 5. The focus of the operating system is on devices where the OS may not directly be visible to the end user, in particular, appliances and cars. The company produces MSN TV, formerly WebTV, a television-based Internet appliance. Microsoft used to sell a set-top Digital Video Recorder (DVR) called the UltimateTV, which allowed users to record up to 35 hours of television programming from a direct-to-home satellite television provider DirecTV. This was the main competition in the UK for bSKYb's SKY + service, owned by Rupert Murdoch. UltimateTV has since been discontinued, with DirecTV instead opting to market DVRs from TiVo Inc. The division includes consumer and Macintosh software, along with computer hardware and entertainment software. Microsoft sells computer games that run on Windows PCs, including titles such as Age of Empires and the Microsoft Flight Simulator series. It produces a line of reference works that include encyclopedias and atlases, under the name Encarta. Microsoft Zone hosts free premium and retail games where players can compete against each other and in tournaments. Microsoft entered the multi-billion-dollar game console market dominated by Sony and Nintendo in late 2001, with the release of the Xbox. As of 2005, the console ranks second to Sony's PlayStation 2 and ahead of Nintendo's GameCube in market share in the United States (although behind the two worldwide). The console shipped 22 million units compared with competitor PlayStation 2 at 90 million units, and the company took a 4 billion dollar loss due to the console . Microsoft develops and publishes its own video games for this console, with the help of its Microsoft Game Studios subsidiary, in addition to "third party" Xbox video-game publishers such as Electronic Arts and Activision, who pay a license fee to publish games for the system. The most recent version of the Xbox is the Xbox 360. Microsoft markets a number of computing-related hardware products, including mice, keyboards, joysticks, and gamepads, along with other game controllers, the production of which is outsourced in most cases. The division houses Microsoft's Macintosh Business Unit, the largest developer of Macintosh software outside Apple itself; it produces such software as Microsoft Office for the Mac (sometimes called "Macintosh Office"), which includes Entourage, a Macintosh-specific application not available in the Windows version of Microsoft Office.

Business culture

Entourage Microsoft has often been described as having a developer-centric business culture. A great deal of time and money is spent each year on recruiting young university-trained software developers who meet very exacting criteria, and on keeping them in the company. For example, while many software companies often place an entry-level software developer in a cubicle desk within a large office space filled with other cubicles, Microsoft assigns a private or semiprivate closed office to every developer or pair of developers. In addition, key decision makers at every level are either developers or former developers. In a sense, the software developers at Microsoft are considered the "stars" of the company in the same way that the sales staff at IBM are considered the "stars" of their company. This culture is reflected in their hiring process—the "Microsoft Interview" is notorious for off-the-wall questions such as "Why is a manhole cover round?" and is a process often mimicked in other organizations. Note that, although they were once ubiquitous, recently fewer interviewers have been using these types of questions. Within Microsoft the expression "eating our own dog food" is used to describe the policy of using the latest Microsoft products inside the company in an effort to test them in "real-world" situations. Only prerelease and beta versions of products are considered dog food. This is usually shortened to just "dog food" and is used as noun, verb, and adjective. For fun, Microsoft also hosts the Microsoft Puzzle Hunt, an annual puzzle hunt (a live puzzle game where teams compete to solve a series of puzzles) held at the Redmond campus. It is a spin-off of the MIT Mystery Hunt. In an ever changing world, Microsoft expects its employees to be comfortable with ambiguity. They may not, for example, know with any degree of certainty when a product will ship, what it will be called, or what features will be included. The business culture expects agile thinkers to rapidly adjust to dramatic changes. Microsoft also fosters a general attitude of long-term strategic wariness in its managers, who are expected to be ready for any challenge from the competition or the market. In this frame of mind, being the largest software company in the world is not seen as a form of safety or a guarantee of future success. For instance, future competitors could rise from other industries, or computer hardware companies could try to become less dependent on Microsoft, or consumers could decide not to upgrade their software as often. Microsoft requires its managers to maintain vigilance and sustain a dynamic expansion in new markets.

User culture

Technical reference for developers and articles for various Microsoft magazines such as Microsoft Systems Journal (or MSJ) is available through Microsoft's MSDN site, short for Microsoft Developer Network. MSDN also offers subscriptions for companies and individuals, and the more expensive subscriptions usually offer access to pre-release beta versions of Microsoft software. In recent years, Microsoft launched a community site for developers and users, entitled Channel9, which provides many modern features such as a wiki and an Internet forum. Most free technical support available through Microsoft is provided through online Usenet newsgroups (in the early days it was also provided on Compuserve). There are several of these newsgroups for nearly every product Microsoft provides, and often they are monitored by Microsoft employees. People who are helpful on the newsgroups can be elected by other peers or Microsoft employees for Microsoft Most Valuable Professional (MVP) status, which entitles people to a sort of special social status, in addition to possibilities for awards and other benefits.

Corporate affairs

Corporate structure

The company is run by its Board of Directors, which consists of ten people, made up of mostly company outsiders (as is customary for publicly traded companies). Current members of the board of directors of Microsoft are: Steve Ballmer, James Cash, Jr., Dina Dublon, Bill Gates, Raymond Gilmartin, Ann Korologos, David Marquardt, Charles Noski, Helmut Panke, and Jon Shirley. The ten board members are elected every year at the annual shareholders' meeting, and those who do not get a majority of votes must submit a resignation to the board, which will subsequently choose whether or not to accept the resignation. There are five committees within the board which have oversight over more specific matters. These committees include the Audit Committee, which handles accounting issues with the company including auditing and reporting; the Compensation Committee, which approves compensation for the CEO and other employees of the company; the Finance Committee, which handles financial matters such as proposing mergers and acquisitions; the Governance and Nominating Committee, which handles various corporate matters including nomination of the board; and the Antitrust Compliance Committee, which attempts to prevent company practices from violating antitrust laws. There are several other aspects to the corporate structure of Microsoft. For worldwide matters there is the Executive Team, made up of sixteen company officers across the globe, which is charged with various duties including making sure employees understand Microsoft's culture of business. The sixteen officers of the Executive Team include the Chairman and Chief Software Architect, the CEO, the General Counsel and Secretary, the CFO, senior and group vice presidents from the business units, the CEO of the Europe, the Middle East and Africa regions; and the heads of Worldwide Sales, Marketing and Services; Human Resources; and Corporate Marketing. In addition to the Executive Team there is also the Corporate Staff Council, which handles all major staff functions of the company, including approving corporate policies. The Corporate Staff Council is made up of employees from the Law and Corporate Affairs, Finance, Human Resources, Corporate Marketing, and Advanced Strategy and Policy groups at Microsoft. Other Executive Officers include the Presidents and Vice Presidents of the various product divisions, leaders of the marketing section, and the CTO, among others.

Stock

When the company debuted its IPO in March 12, 1986, the stock price was $22. By the close of the first trading day, the stock had closed at twenty-eight dollars, or 97c, compared with the time period after the company's first nine splits. The initial close and ensuing rise in subsequent years made several Microsoft employees millions. The stock price peaked in 1999 at around 119 dollars (60,928 dollars adjusting for splits). While the company has had nine stock splits, the first of which was in September 18, 1987, the company did not start offering a dividend until January 16, 2003. The dividend for the 2003 fiscal year was eight cents per share, followed by a dividend of sixteen cents per share the subsequent year. The company switched from quarterly to yearly dividends in 2005, for eight cents a share per quarter with a special one-time payout of three dollars per share for the second quarter of the fiscal year. Around 2002 the stock price began a slow descent that continued through 2005. The company had its ninth split on February 2, 2003, in what could have been an attempt to arouse interest in the stock, but the price continued to stagnate regardless. On the September 23, 2005, episode of CNBC's Mad Money, the host of the show, Jim Cramer, called Microsoft's stock "the most hated stock on Wall Street".

Diversity

Microsoft received a 86% rating in the 2004 Corporate Equality Index from the Human Rights Campaign relating to its policies concerning LGBT (lesbian, gay, bisexual and transsexual) employees. According to the Human Rights Campaign, this was in line with the industry standard . Through the work of the Gay and Lesbian Employees at Microsoft (GLEAM) group and Diversity, Microsoft added gender expression to its antidiscrimination policies in April 2005, and the Human Rights Campaign upgraded Microsoft's Corporate Equality Index rating to 100%, putting it among the most progressive companies in the world. Microsoft also received criticism from the Human Rights Campaign and many others in April 2005 for withdrawing support for Washington's H.B. 1515 bill that would extend the state's current antidiscrimination laws to people with alternate sexual orientations. However, under harsh criticism from both outside and inside the company's walls, Microsoft eventually supported the bill again in May 2005 . Even though it hires many domestic American workers, Microsoft generally goes up to the annual limit in hiring foreign workers with H1B visas. Bill Gates has criticized Congress for the cap on the H1B visas, which he claims makes it difficult to hire employees for the company. Proponents of the cap cite economic and security reasons for the current law. Microsoft was also named one of the 100 Best Companies for Working Mothers in 2004 by Working Mother magazine.

Logo

Working Mother In 1987, Microsoft adopted its current logo, the so-called "Pacman Logo" designed by Scott Baker. According to the March 1987 Computer Reseller News Magazine, "The new logo, in Helvetica italic typeface, has a slash between the o and s to emphasize the "soft" part of the name and convey motion and speed." Employees ran a campaign to save the old logo, which was green, in all uppercase, and featured a fanciful letter O nicknamed the blibbet, but it was nevertheless discarded.

Criticism

Working Mother Microsoft has been the focus of much controversy in the computer industry, especially since the 1980s; in particular, which some some think its business tactics as unfair and anticompetitive. Some describe Microsoft's business tactics as "embrace, extend and extinguish", in which Microsoft initially embraces and extends a competing standard or product, only to later extinguish it through such actions as writing their own incompatible version of the software or standard. Microsoft has also been called a "velvet sweatshop" in reference to the company working its employees to the point where it might be bad for their health. The first instance of the term in reference to Microsoft originated from a Seattle Times article in 1989, and later became used to describe the company by some of Microsoft's own employees. In rulings following antitrust litigation, U.S. courts ruled that Microsoft is an abusive monopoly, and the company endures legal attacks along these lines in many countries around the world; these are successful to varying degrees, but have not yet forced serious reform such as forcing a separation of the company. Some also accuse Microsoft of allowing the user interface of its products to become inconsistent and overly complicated, requiring interactive "wizards" to function as an extra layer between the user and the interface. The security of Microsoft products (such as Internet Explorer) is also questioned by some as being overly vulnerable to computer viruses and malicious attacks. In addition, proponents of free software are engaged with Microsoft in a debate over the Total cost of ownership (TCO) of its products, as some perceive Microsoft software as more expensive to purchase, use and maintain than competitors' software. A July, 2003 article in the New York Times, accused Microsoft founder, Bill Gates, of stealing ideas for the development of Windows from its competitor, Apple. Microsoft has also been criticized for its end user license agreements, which some believe are too restrictive. As detailed in this article, Microsoft has purchased the products of many other companies to market as its own. It has also duplicated the innovations of other companies (Apple in particular) in products which have in many cases gone on

Computer cluster

]] A computer cluster is a group of loosely coupled computers that work together closely so that in many respects it can be viewed as though it were a single computer. Clusters are commonly (but not always) connected through fast local area networks. Clusters are usually deployed to improve speed and/or reliability over that provided by a single computer, while typically being much more cost-effective than single computers of comparable speed or reliability.

Cluster categorizations

High-availability (HA) clusters

High-availability clusters are implemented primarily for the purpose of improving the availability of services which the cluster provides. They operate by having redundant nodes which are then used to provide service when system components fail. The most common size for an HA cluster is two nodes, which is the minimum required to provide redundancy. HA cluster implementations attempt to manage the redundancy inherent in a cluster to eliminate single points of failure. There are many commercial implementations of High-Availability clusters for many operating systems. The Linux-HA project is one commonly used free software HA package for the Linux OS.

Load balancing clusters

Load balancing clusters operate by having all workload come through one or more load-balancing front ends, which then distribute it to a collection of back end servers. Although they are implemented primarily for improved performance, they commonly include high-availability features as well. Such a cluster of computers is sometimes referred to as a server farm. There are many commercial load balancers available including Moab Cluster Suite and Maui Cluster Scheduler. The Linux Virtual Server project provides one commonly used free software package for the Linux OS.

High-performance (HPC) clusters

High-performance clusters are implemented primarily to provide increased performance by splitting a computational task across many different nodes in the cluster, and are most commonly used in scientific computing. One of the more popular HPC implementations is a cluster with nodes running Linux as the OS and free software to implement the parallelism. This configuration is often referred to as a Beowulf cluster. Such clusters commonly run custom programs which have been designed to exploit the parallelism available on HPC clusters. Many such programs use libraries such as MPI which are specially designed for writing scientific applications for HPC computers. HPC clusters are optimized for workloads which require jobs or processes happening on the separate cluster computer nodes to communicate actively during the computation. These include computations where intermediate results from one node's calculations will affect future calculations on other nodes.

Grid Computing

Grid computing or grid clusters are a technology closely related to cluster computing. The key differences between grids and traditional clusters are that grids connect collections of computers which do not fully trust each other, and hence operate more like a computing utility than like a single computer. In addition, grids typically support more heterogeneous collections than are commonly supported in clusters. Grid computing is optimized for workloads which consist of many independent jobs or packets of work, which do not have to share data between the jobs during the computation process. Grids serve to manage the allocation of jobs to computers which will perform the work independently of the rest of the grid cluster. Resources such as storage may be shared by all the nodes, but intermediate results of one job do not affect other jobs in progress on other nodes of the grid.

High-performance cluster implementations

The TOP500 organization publishes the 500 fastest computers twice a year, usually including many clusters on their list. TOP500 [http://top500.org] is a collaboration between the University of Mannheim, the University of Tennessee, and the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory. The current top supercomputer is the Department of Energy's BlueGene/L system with performance of 280.6 TFlops. The second place is owned by another BlueGene/L system with performance of 91.29 TFlops. Clustering can provide significant performance benefits versus price. The System X supercomputer at [http://www.tcf.vt.edu/systemX.html Virginia Tech], the seventh most powerful supercomputer on Earth as of November 2004, is a 12.25 TFlops computer cluster of 1100 Apple XServe G5 2.3 GHz dual processor machines (4 GB RAM, 80 GB S-ATA HD) running Mac OS X. The cluster initially consisted of Power Mac G5s; the XServe's are smaller, reducing the size of the cluster. The total cost of the previous Power Mac system was $5.2 million, a tenth of the cost of slower mainframe supercomputers. The Power Mac G5s were sold off. The central concept of a Beowulf cluster is using COTS computers to produce a cost-effective alternative to a traditional supercomputer. One project that took this to an extreme was the Stone Soupercomputer. John Koza has the largest computer cluster owned by an individual.

Cluster history

The first commodity clustering product was ARCnet, developed by Datapoint in 1977. ARCnet wasn't a commercial success and clustering didn't really take off until DEC released their VAXcluster product in the 1980s for the VAX/VMS operating system. The ARCnet and VAXcluster products not only supported parallel computing, but also shared file systems and peripheral devices. They were supposed to give you the advantage of parallel processing while maintaining data reliability and uniqueness. VAXcluster, now VMScluster, is still available on OpenVMS systems from HP running on Alpha and Itanium systems. The history of cluster computing is intimately tied up with the evolution of networking technology. As networking technology has become cheaper and faster, cluster computers have become significantly more attractive.

Cluster technologies

MPI is a widely-available communications library that enables parallel programs to be written in C and Fortran, for example, in the climate modeling program MM5. The GNU/Linux world sports various cluster software, such as:
- Beowulf, distcc, MPICH and other - mostly specialized application clustering. distcc provides parallel compilation when using GCC.
- Linux Virtual Server, Linux-HA - director-based clusters that allow incoming requests for services to be distributed across multiple cluster nodes.
- Mosix, openMosix, Kerrighed, OpenSSI - full-blown clusters integrated into the kernel that provide for automatic process migration among homogenous nodes. OpenSSI and Kerrighed are single-system image implementations. DragonFly BSD, a recent fork of FreeBSD 4.8 is being redesigned at its core to enable native clustering capabilities. It also aims to achieve single-system image capabilities. MSCS is Microsoft's high-availability cluster service for Windows. Based on technology developed by Digital Equipment Corporation. The current version supports up to eight nodes in a single cluster, typically connected to a SAN. A set of APIs support cluster-aware applications, generic templates provide support for non-cluster aware applications.

Clustering software (open source)

- TORQUE Resource Manager, [http://www.clusterresources.com/products/torque/]
- Maui Cluster Scheduler [http://www.clusterresources.com/products/maui/]
- OpenSSI High-availability, load-balancing, and high-performance clustering with or without a SAN.
- Sun GridEngine
- OpenMosix
- OpenSCE [http://www.opensce.org/]
- Open Source Cluster Application Resources (OSCAR) [http://oscar.openclustergroup.org/]
- Rocks Cluster Distribution [http://www.rocksclusters.org/]
- WareWulf [http://warewulf.lbl.gov/pmwiki/]
- Linux-Cluster Project [http://sources.redhat.com/cluster/] Global File System & HA

Clustering products

- Moab Cluster Suite [http://www.clusterresources.com/products/moabclustersuite.shtml]
- Linux-HA
- KeyCluster
- Novell Cluster Services, [http://www.novell.com/documentation/oes/index.html?page=/documentation/oes/cluster_admin_lx/data/h4r4bw6c.html Novell Cluster Services for Linux and NetWare]
- IBM's HACMP
- Microsoft Cluster Server (MSCS)
- Red Hat Cluster
- Sun N1 GridEngine [http://www.sun.com/software/gridware/ Sun N1 GridEngine]
- MC Service Guard for HP-UX systems
- SteelEye LifeKeeper
- Oracle Real Application Cluster (RAC)
- PolyServe
- Veritas Cluster Server (VCS), from VERITAS Software
- BOINC

References

- Greg Pfister: In Search of Clusters, Prentice Hall, ISBN 0138997098
- Evan Marcus, Hal Stern: Blueprints for High Availability: Designing Resilient Distributed Systems, John Wiley & Sons, ISBN 0471356018
- Karl Kopper: The Linux Enterprise Cluster: Build a Highly Available Cluster with Commodity Hardware and Free Software, No Starch Press, ISBN 1593270364

External links

- [http://lcic.org/ Linux clustering information center]
- [http://linux-ha.org/CommercialSoftware List of commercial HA clustering Software for Linux]
- [http://www.linuxhpc.org/ LinuxHPC]
- [http://www.beowulf.org/ Beowulf]
- [http://www.top500.org/ Top 500 Supercomputer List]
- [http://www.cs.sandia.gov/cplant Cplant, a non-Beowulf Linux cluster]
- [http://www.ieeetfcc.org/ IEEE task force on cluster computing, the leading academic community on cluster computing]
- [https://cajo.dev.java.net The cajo project] Free clustered computing using Java. (LGPL)
- [http://www.windowsnetworking.com/articles_tutorials/Cluster-Quorums.html Understanding How Cluster Quorums Work]
- [http://www.clusterbuilder.org Cluster Builder]- Research for building a cluster
- [http://www.sun.com/software/grid Sun Grid Computing Solutions]
- [http://www.clusterresources.com Cluster Resources]
- [http://www.clustermonkey.net ClusterMonkey] - On-line Cluster magazine
- [http://bofh.be/clusterknoppix/ ClusterKnoppix]

Cluster sites

- [http://teragrid.ncsa.uiuc.edu/TGIA64LinuxCluster.html Teragrid]
- [http://www.westgrid.ca/support/topics/scheduling.php WestGrid]
- [http://www.tcf.vt.edu/systemX.html ViriginaTech]
- [http://www.irb.hr/en/cir/projects/dcc/00006/ IRB]
- [http://www.sara.nl/userinfo/lisa/usage/batch/index.html SARA] Category:Computer networks Category:Parallel computing ko:컴퓨터 클러스터 ja:コンピュータ・クラスター

Load balancing

In computing, load balancing is a technique used to spread work between many processes, computers, disks or other resources.

Web server load balancing

One major issue for large Internet sites is how to handle the load of the large number of visitors they get. This is routinely encountered as a scalability problem as a site grows. There are several ways to accomplish load balancing; an example of a site using the approach is the Wikimedia Foundation and its projects. In June 2004 the load was balanced using a combination of:
- Round robin DNS distributed page requests evenly to one of three Squid cache servers.
- Squid cache servers used response time measurements to distribute page requests between seven web servers. In addition, the Squid servers cached pages and delivered about 75% of all pages without ever asking a web server for help.
- The PHP scripts which run the web servers distribute load to one of several database servers depending on the type of request, with updates going to a master database server and some database queries going to one or more slave database servers. Alternative methods include use of layer 4 routers, and for Linux, the Linux Virtual Server, which is an advanced open source load balancing solution for network services. Network Load Balancing Services is a Microsoft proprietary clustering and load balancing implementation.

Network load balancing and redundancy

When providing an online service, it is important to always have access to the Internet. You cannot limit yourself to choosing one provider and being at their mercy. They may fail or you may overload the circuit with peak traffic during the day, resulting in slower network speed. Unavailability when a site is down and slow connections can cause clients to go elsewhere, perhaps to your competition for better service. Many sites are turning to the multi-homed scenario; having multiple connections to the Internet via multiple providers to provide a reliable and high throughput service. Multi-homed networks are increasing in popularity because they provide networks with better reliability and performance to the end-user. Better reliability results from the fact that the network is protected in case one of the Internet links or access routers fails. Performance increases due to the fact that the network's bandwidth to the Internet is the sum of the different pipes available through the different access links.

Vendors providing web server load balancing solutions

- [http://www.cisco.com/en/US/partner/netsol/ns340/ns394/ns50/ns254/networking_solutions_package.html/ Cisco Systems]
- [http://www.coyotepoint.com/ Coyote Point Systems]
- [http://www.f5.com/ F5 Networks]
- [http://www.inlab.de/balanceng/index.html Inlab Software GmbH]
- [http://www.kemptechnologies.com/ KEMP Technologies, Inc]
- [http://www.netscaler.com/ Netscaler, Inc.]
- Radware
- [http://www.zeus.com/ Zeus Technology]

Vendors providing cluster, grid and HPC load balancing solutions

- [http://clusterresources.com/ Cluster Resources]

Vendors providing network load balancing and redundancy

- Radware

References

- Tony Bourke: Server Load Balancing, O'Reilly, ISBN 0-596-00050-2
- Robert J. Shimonski: Windows Server 2003 Clustering & Load Balancing, Osborne McGraw-Hill, ISBN 0-07-222622-6
- Jeremy Zawodny, Derek J. Balling: High Performance MySQL, O'Reilly, ISBN 0-596-00306-4

External links

- [http://wwwcs.uni-paderborn.de/cs/ag-monien/RESEARCH/LOADBAL/ Dynamic Load Balancing and Scheduling]
- [http://lcic.org/load_balancing.html Load Sharing and Balancing]
- [http://www.zib.de/projects/telecommunication/STP/index.en.html Load Balancing in Signaling Transfer Points]
- [http://sqlrelay.sourceforge.net/ SQL Relay]
- [http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/TechRef/6ac4a6ba-1c0c-46be-8c6a-2c2e0e567e98.mspx What Is Network Load Balancing?]
- Article "[http://www.linux.com/article.pl?sid=05/07/27/1729229 Taking a load off: Load balancing with balance]" by Costa Walcott
- Paper "[http://doi.ieeecomputersociety.org/10.1109/EDOC.2004.10020 Evaluating the Performance of Middleware Load Balancing Strategies]" by Jaiganesh Balasubramanian, Douglas C. Schmidt, Lawrence Dowdy and Ossama Othman
- [http://www.omg.org/gettingstarted/orb_basics.htm#g:LoadBalancing How does CORBA support load-balancing?]
- [http://citeseer.ist.psu.edu/cis?q=load+balancing Citations by CiteSeer] Category:Computing

Virtual private network

A Virtual Private Network, or VPN, is a private communications network usually used within a company, or by several different companies or organizations, to communicate over a public network. VPN message traffic is carried on public networking infrastructure (e.g. the Internet) using standard (often insecure) protocols, or over a service provider's network providing VPN service guarded by well defined Service Level Agreement (SLA) between the VPN customer and the VPN service provider.

Authentication mechanism

Generally, a firewall sits between a remote user's workstation or client and the host network or server. The firewall may pass authentication data to an authentication service in a host network. A known trusted person with privileged access, sometimes only using trusted devices, can be allowed to access resources not available to general users. That's why the user feels that the network is private, even though it is not. Many VPN client programs can be configured to require that all IP traffic must pass through the tunnel while the VPN is active, for better security. From the user's perspective, this means that while the VPN client is active all access outside their employer's secure network must pass through the same firewall as would be the case while physically connected to the office ethernet. This reduces the risk that an attacker might gain access to the secured network by attacking the employee's laptop: to other computers on the employee's home network, or on the public internet, it is as though the machine running the VPN client simply does not exist. Such security is important because other computers local to the network on which the client computer is operating may be untrusted or partially trusted. Even with a home network that is protected from the outside internet by a firewall, people who share a home may be simultaneously working for different employers over their respective VPN connections from the shared home network. Each employer would therefore want to ensure their proprietary data is kept secure, even if another computer in the local network gets infected with malware. And if a travelling employee uses a VPN client from a Wi-Fi access point in a public place, such security is even more important.

Types of VPNs

Secure VPNs use cryptographic tunneling protocols to provide the necessary confidentiality (preventing snooping), sender authentication (preventing identity spoofing), and message integrity (preventing message alteration) to achieve the privacy intended. When properly chosen, implemented, and used, such techniques can provide secure communications over unsecured networks. Because such choice, implementation, and use are not trivial, there are many insecure VPN schemes on the market. Secure VPN technologies may also be used to enhance security as a "security overlay" within dedicated networking infrastructures. Secure VPN protocols include the following:
- IPsec (IP security), an obligatory part of IPv6.
- SSL used either for tunneling the entire network stack, such as in OpenVPN, or for securing what is essentially a web proxy. Although the latter is often called a "SSL VPN" by VPN vendors, it is not really a fully-fledged VPN.
- PPTP (point-to-point tunneling protocol), developed jointly by a number of companies, including Microsoft. Some large ISPs now offer "managed" VPN service for business customers who want the security and convenience of a VPN but prefer not to undertake administering a VPN server themselves. In addition to providing remote workers with secure access to their employer's internal network, sometimes other security and management services are included as part of the package, such as keeping anti-virus and anti-spyware programs updated on each client's computer. Trusted VPNs do not use cryptographic tunneling, and instead rely on the security of a single provider's network to protect the traffic. Multi-protocol label switching (MPLS) is commonly used to build trusted VPNs. Other protocols for trusted VPNs include:
- L2F (Layer 2 Forwarding), developed by Cisco.
- L2TP (Layer 2 Tunnelling Protocol), including work by both Microsoft and Cisco.
- L2TPv3 (Layer 2 Tunnelling Protocol version 3).

Characteristics in application

A well-designed VPN can greatly benefit a company. For example, it can:
- Extend geographic connectivity.
- Improve security where data lines have not been ciphered.
- Reduce operational costs versus traditional WAN.
- Reduce transit time and transportation costs for remote users.
- Simplify network topology in certain scenarios.
- Provide global networking opportunities.
- Provide telecommuter support.
- Provide broadband networking compatibility.
- Provide faster ROI (return on investment) than traditional carrier leased/owned WAN lines.
- Show a good economy of scale.
- Scale well, when used with a PKI (Public Key Infrastructure). However, since VPNs extend the "mother network" by such an extent (almost every employee) and with such ease (no dedicated lines to hire), there are certain security implications that have to receive special attention:
- Security on the client side has to be tightened and enforced. Keywords: Central Client Administration, Security Policy Enforcement. It is common for a company to require that each employee wishing to use their VPN from home first install an approved hardware firewall.
- The scale of access to the target network may have to be limited.
- Logging must be evaluated and in most cases revised.

Tunneling

Tunneling, also known as "port forwarding", is the transmission of data intended for use only within a private, usually corporate network through a public network in such a way that the routing nodes in the public network are unaware that the transmission is part of a private network. Tunneling is generally done by encapsulating the private network data and protocol information within the public network transmission units so that the private network protocol information appears to the public network as data. Tunneling allows the use of the Internet, which is a public network, to convey data on behalf of a private network.

External links

- [http://vpn.shmoo.com/ VPN resources]
- [http://www.vpnc.org/ Virtual Private Network Consortium]
- [http://www.vpnlabs.org/ VPN Labs]
- RFC 2764 - A Framework for IP Based Virtual Private Networks
- [http://openvpn.net/ OpenVPN, an open source VPN program] Category:Computer networks Category:Internet privacy ja:Virtual Private Network

Category:Computer networks

This category contains articles related to computer networks. Networks Category:Networks Category:Data transmission Category:Electronic engineering Category:Communication ja:Category:コンピュータネットワーク

Category:Netware

NetWare is a network operating system and the set of network protocols it uses to talk to client machines on the network. Developed by Novell, it was widely used in the late 1980s and early 1990s, but lost much of its market share to Windows NT and Linux. Category:Operating systems Category:Network-related software

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