| | Many programmers dread the thought of handling network timeouts. A common fear is that a simple, single-threaded network client without timeout support will balloon into a complex multithreaded nightmare, with separate threads needed to detect network timeouts, and some form of notification process at work between the blocked thread and the main application. While this is one option for developers, it is not the only one. Dealing with network timeouts need not be a difficult task, and in many cases you can completely avoid writing code for additional threads. This article shows how esy it is to write code that handles network timeouts gracefully. | Compute grids emerged as the primary architecture for such batch-oriented, highly parallel jobs. Due to the batch-oriented, occasional nature of such workloads, for many businesses an in-house grid would enjoy poor overall utilization, according to Sun's Rohit Valia, manager of Network.com, the company's on-demand network-based grid computing utility. | The article's final example summarizes the key config model capabilities. All of the Sun-contributed Jini 2.0 Starter Kit service implementations have persistent modes . They also offer administrative proxies that implement JoinAdmin. JoinAdmin's methods allow clients to set the groups and locators the service must use for discovery. The services' administrative proxies expect those changes to be part of the service's persisted state. | How Jini works Jini defines a runtime infrastructure that resides on the network and provides mechanisms that enable you to add, remove, locate, and access services. The runtime infrastructure resides on the network in three places: in lookup services that sit on the network; in the service providers (such as Jini-enabled devices); and in clients. Lookup services are the central organizing mechanism for Jini-based systems. When new services become available on the network, they register themselves with a lookup service. When clients wish to locate a service to assist with some task, they consult a lookup service. | Write an application named GetServer.java that creates a ServerSocket on port 80. When a client request comes in, get an InputStream from the socket returned by read lines from the ServerSocket's accept() method, and wrap the InputStream in an InputStreamReader and a BufferedReader. Read one line at a time from the BufferedReader while the length of the line read does not equal 0 and the first character is not '\r' or '\n'. Each time you read a line from the BufferedReader, print the line out to the standard output. Once you are done reading lines, just close the socket by closing the BufferedReader. | The shift away from the mainframe model towards the distributed processing model was a consequence of the personal computer revolution, which was made possible by the rapidly increasing capabilities and decreasing costs of processors. Similarly, lurking underneath the latest software paradigm shift towards distributed processing with network-mobile code is another hardware trend--the increasing capabilities and decreasing costs of network bandwidth. As bandwidth, the amount of information that can be carried by a network, increases, it becomes practical to send new kinds of information across a network; and with each new kind of information a network carries, the network takes on a new character. Thus, as bandwidth grows, simple text sent across a network can become enhanced with graphics, and the network begins to take on an appearance reminiscent of newspapers or magazines. Once bandwidth expands enough to support live streams of audio data, the network begins to act like a radio, a CD-player, or a telephone. With still more bandwidth, video becomes possible, resulting in a network that competes with TV and VCRs for the attention of couch potatoes. But there is still one other kind of bandwidth-hungry content that becomes increasingly practical as bandwidth improves: computer software. Because networks by definition interconnect processors, one processor can, given enough bandwidth, send code across a network for another processor to execute. Once networks begin to move software as well as data, the network begins to look like a computer in its own right. | Whether you're an employee in Corporate America or run a home network, chances are you're very familiar with two of the biggest impediments to end-to-end Internet transparency: NAT devices (a technology known as "Internet Connection Sharing" in the Microsoft world) and firewalls. These devices are popular because they increase security and simplify connectivity and network management for home users and network administrators. Unfortunately, they cause problems for fine-grained distributed applications in the P2P, mobile agent, and grid computing spaces that have to extend across the network boundaries that these devices define. | | Let's begin by examining the ideal, perfectly transparent network, shown in Figure 1. I'll use this as the departure point for studying network obstructions that we must work around. | Fortunately, the designers of the Java platform built networking into the language. It offers a safe, proven mechanism for working around the constraints of the firewall. In this article, I will show you how to use Java Servlet technology to create a tunnel to the business layer of your corporate network. At the end of the article, I will discuss other servlet-based methods of tunneling through the corporate firewall, including a quick run-down of the potential benefits and drawbacks of each method. | Networking in Java programming includes the ability to locate and identify resources and communicate over TCP and UDP connections. First you need to identify the resource with a name like www.ibm.com, then open a connection to that resource, and finally send packets between yourself and the other end of the connection. Additional tasks may be involved for the sake of security, but the overall process stays the same. With the Java platform, the classes to support these operations are found in the java.net package. From the early days of Java programming to the present, most of these operations haven't changed much. With Merlin, though, some of these basic operations have improved to support new and worthwhile features. In this article, we'll look at five such features: IPv6 support, URIs, network interfaces, unbound sockets, and secure sockets. | The technology JMX (Java Management eXtensions) is a rather new Sun Microsystemss standard that allows Java developers to integrate their applications with existing solutions of network management. JMX defines the standard for a creating of JMX-objects, so-called MBeans. MBeans "live" inside the container. Thus, any JMX client (a remote or local application can act as such a client, for example) has an ability to call methods and to get access to MBeans attributes with the help container in which they are located. The application also can receive special notices (messages) from MBeans if this application registers corresponding MBeans. | Telecommunication software is on the verge of a revolution. Closed, proprietary programming environments are giving way to an open, extensible, reusable and services-oriented framework based on Java. JAIN ? The Java Advanced Intelligent Network effort promises to bring service portability, secure network access, and network integration to the world of telecom and Internet networks. The JAIN effort will define standard Java interfaces and environments for service creation, testing, management, and deployment over wireless, PSTN, IP, and other networks. | Cable companies quickly realized that the Web was not a challenge to their once lofty set-top box goals. The Web perhaps was a catalyst by demonstrating the viability of networked, electronic content. The cable companies also realized that all those underground cables to millions of homes could be used to deliver Web content at high speed. All that was needed was a set-top box that could understand Internet protocol and support Web browsing software. Proprietary software could be developed, but an open standard is more consistent with the Web paradigm. TCI, a leading cable company, has chose the Java platform for use in set-top boxes. With Java, any developer can extend the functionality of a set-top box by writing Java applets. | Service-driven networking requires rapid automated provisioning in response to user demand. Suppose you want to increase your allocated bandwidth or you want to access the latest broadband game from your service provider. Typically, you must complete an online form and a provisioning server updates your profile. Then you need access to the required resources. Service providers are falling over themselves to achieve this type of rapid customer response! Speed and accuracy of order fulfillment is of the essence. | We’ll see most of these in the following discussion. Figure 1 illustrates a corporate HQ with a remote branch office interconnected by a service provider network. The HQ site enterprise architecture supports a range of applications, including voice-over-IP (VoIP), video-over-IP, email, etc. Access to these applications is available over the MPLS-based service provider network. | As demands placed on data centers grow, blade servers provide a convenient means of massively extending the device density. As with any technology, you gain in one way and lose in another; the increased density places a greater burden on the human operator. It's entirely possible that the problems of blade management may usher in the "next big thing" in the form of autonomic computing. Whether or not this happens, the key element that will assure the success of blade technology is the management software. | In the normal course of events, network device technology (IP/MPLS, layer 2/3 VPN, VPLS, and so on) is developed, and only later does management information base (MIB) design commence. The major theme of this article is that network management operational workflows should play a greater role in driving MIB design. A simple example discussed is the creation of an IP/MPLS RFC2547 VPN, where it's not currently very easy to define end-to-end quality of service for many VPNs. A recent addition to the MIB has improved this situation, which means that if a VPN site has real-time traffic to send to another site, it's no longer so very difficult to guarantee availability of the required resources. This change shows that designing MIBs with workflows in mind facilitates a better match between network management and the services deployed in the network. |
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