A private branch exchange(PBX) is a telephone exchange that serves a particular business or office, as opposed to one that a common carrier or telephone company operates for many businesses or for the general public. PBXs are also referred to as:
PBXs make connections among the internal telephones of a private organization — usually a business — and also connect them to the public switched telephone network (PSTN) via trunk lines. Because they incorporate telephones, fax machines, modems, and more, the general term “extension” is used to refer to any end point on the branch.
PBXs are differentiated from “key systems” in that users of key systems manually select their own outgoing lines, while PBXs select the outgoing line automatically. Hybrid systems combine features of both.
Initially, the primary advantage of PBXs was cost savings on internal phone calls: handling the circuit switching locally reduced charges for local phone service. As PBXs gained popularity, they started offering services that were not available in the operator network, such as hunt groups, call forwarding, and extension dialing. In the 1960s a simulated PBX known as Centrex provided similar features from the central telephone exchange.
UGP provides users the ability to run interactive GUI applications on the cluster compute nodes and to interact with these applications via their web browsers. UGP impliments this by using VNC, a program that allows users to interact with interactive programs accross the network. To use VNC, UGP runs the VNC Server on the cluster compute node as the user and the VNC Viewer applet in the users web browser. All the tasks normally required to run VNC, such as the generation of a VNC password for the user, the creation of a VNC startup file, etc., are taken care of for the user by UGP.
The following is the steps when the user runs xterm in the browser:
Runs the VNC Server as the user on the cluster compute node. It does this by using Globus GRAM to start up a fork job on the Grid Appliance conected to the cluster. The fork job, SSHs to the compute node where it starts up the VNC Server. As part of starting up the VNC Server, UGP generates a random password for VNC, and places all necessary files in a subdirectory of the .vnc directory under the user’s login id.
Runs the VNC Viewer Applet in the user’s web browser, passing it the VNC password and a port and address that it is to use to communicate with the VNC Server.
The Internet is transforming society and business. The current wave of this technology revolution, called Web 2.0, followed the initial wave (Web 1.0) that collapsed with the dot.com boom and bust. Today, ‘always-on’, pervasive broadband is making access to the Internet easy enough for it to be no longer considered as a ‘technology’ but parts of the fabric of modern living, like the telephone or television. The key advantages of using the Internet can be summed up as ‘always on and everywhere’, reachable from mobile devices, laptops, and desktop machines.
Innovations in modern browsers allowed vendors to build the first RWA: applications which could split the application logic between presentation logic that runs on the client-side and business logic and data models that run on the server-side. The rich Web application User Interface (UI) is as ‘rich’ as in desktop applications, and runs in the browser using a combination of languages. One of the pioneering vendors – Adaptive Systems – called this approach Asynchronous JavaScript and XML (AJAX – although the preferred naming culture is now just Ajax). All modern browsers support JavaScript and this means that with Ajax there is just a small JavaScript rendering engine which is downloaded and held in memory while the application is running.
The field of Web conferencing software is growing at a breathtaking pace. In the summer of 1994 there were exactly two products in this category, both of them rather primitive freeware packages. Today there are well over 60 commercial and freeware products, many of them quite sophisticated, that support conferencing on the Web in one form or another.
With so many products available, the choice can seem overwhelming. But with a methodical approach, you’ll probably find that you can quickly whittle the list down to just a few candidates.
First, let’s define our terms. For our present purposes, conferencing is a form of group discussion that uses text messages stored on a computer as a communication medium. It does not include various types of real-time, or synchronous, communication, such as “chat rooms”, voice-based teleconferencing, or video conferencing.
A conferencing system is Web-based if it uses Web browsers and servers to provide most of its functionality. This is not as clear a distinction as it might sound. Most developers of conferencing software are hurrying to adapt their products to the Web, and the result is a lot of hybrid products that use the Web to a greater or lesser extent. Hence, the boundary between Web and non-Web conferencing software is a bit blurry.
Asterisk is a software implementation of a telephone private branches exchange (PBX) originally created in 1999 by Mark Spencer of Digium. Like any PBX, it allows attached telephones to make calls to one another, and to connect to other telephone services including the public switched telephone network (PSTN) and Voice over Internet Protocol(VoIP) services. Its name comes from the asterisk symbol, “*”.
Asterisk solutions is released under a dual license model, using the Genera Public License (GPL) as a free software license and a proprietary software license to permit licensees to distribute proprietary, unpublished system components.
Due to free licensing of the software, hundreds of community programmers have contributed features and functionality and have reported and corrected bugs. Originally designed for Linux, Asterisk now also runs on a variety of different operating systems including NetBSD, OpenBSD, FreeBSD, Mac OS X, and Solaris. A port to Microsoft Windows is known as AsteriskWin.
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Flex is a software development kit released by Adobe Systems for the development and deployment of cross-platform rich Internet applications based on the Adobe Flash platform. Flex applications can be written using Adobe Flex Builder or by using the freely available Flex compiler from Adobe.
The initial release in March 2004 by Macromedia included a software development kit, an IDE, and a J2EE integration application known as Flex Data Services. Since Adobe acquired Macromedia in 2005, subsequent releases of Flex no longer require a license for Flex Data Services, which has become a separate product rebranded as LiveCycle Data Services.
Flex is a highly productive, free open source framework for building and maintaining expressive web applications that deploy consistently on all major browsers, desktops, and operating systems. While Flex applications can be built using only the free open source framework, developers can use Adobe Flex Builder software to dramatically accelerate development.
