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Trust Center. Whenever it happens, most surfers quickly move on. To keeps things fresh, Web designers are constantly updating and rereleasing versions of their Web sites sometimes every month or two unlike the historical 12 to 18 month development cycle of desktop software. Because developers are pushing code out the door so quickly, it's not always tested thoroughly. Consequently, the onus of robustness and reliability is transferring from the specific Web software to the system.
This is also one of the primary thrusts behind the. NET Common Language Runtime—to push the responsibility for mundane, easily overlooked details down to the system. IIS also actively recycles stops and restarts processes as necessary while continuing to manage requests without interrupting the experience on the client end.
To enable this, IIS 6. The idea behind IIS 6. These application pools define a set of Web applications that share one or more worker processes; each application pool is separated from other pools naturally by standard Win32 process boundaries. The application pools remain independent of each other, and an application in one pool is not affected by other application pools. Application pools effectively serve as namespace groups. Figure 5 illustrates the worker process isolation mode of IIS.
Figure 5 Worker Process Isolation Mode The worker processes operate independently of each other so they can fail without affecting other worker processes via the natural Windows process boundary.
The pooling of applications protects them from the impact of failing worker processes. If application isolation is the first part of the robustness story, the second part is kernel-level queuing. The kernel-mode HTTP service is also responsible for overall connection management, bandwidth throttling, and text-based logging. By implementing a cache, the service handle caches HTTP responses completely in kernel mode with no transition to user mode, thereby greatly improving performance.
The URI namespace mechanism implemented by http. Each application pool has its own request queue within http. Because no user-mode code runs within http. Even if an accident happens within the user mode request processing infrastructure, http. Even if a worker process crashes, it's not a big deal because whenever the W3SVC notices a crashed worker process, it starts a new instance of the process.
Thus, while there may be a temporary disruption in the ability to process user mode requests, the user doesn't experience the failure because requests continue to be accepted and queued within http. With the advent of application pooling and kernel mode queuing, IIS 6. Because pools are separated by worker process boundaries, an application in one pool is not affected by problems caused by applications in other pools.
Finally, the component that ties together the application pools and the kernel mode queuing is the Web Administration Service WAS. WAS and http. Both are isolated from user-mode code by standard Win32 process boundaries outside user mode and thereby remain unaffected by accidents within the Web application code, unlike IIS 5.
As a result, with IIS 5. Self healing IIS 6. Scalability IIS 6. Automated debugging IIS 6. In the next sections, I'll explain how these improvements work. As you know, humans can go only so far in reducing errors in a program. We can come close, but it takes a tremendous amount of effort to test and make sure a program works as it should.
Certain types of programs must work as advertised and stay up and running for extended periods of time, like Windows —you turn on your box and often don't need to reboot until some piece of installation software tells you it wants you to. On the other end of the spectrum is the class of Web-based content providers. The goal behind most sites delivering content is to ship early and often. Often this means that the testing part of the development process suffers.
Sometimes these apps may spring nasty memory leaks or other similarly sneaky bugs that violate the integrity of the process space in which it runs. In this case, IIS can detect these inconsistencies and crash in user mode. It then proactively recycles application pools. You can configure IIS to periodically restart worker processes within an application pool. By specifying that an application be recycled, you basically tell IIS to shut down the process space and create a new one at various intervals.
So if you know that one application has a problem such as a memory leak, you may recycle the application, every hour perhaps. Because HTTP is a disconnected protocol, one instance of an application process space can often handle requests just as well as another.
These broken, recycled applications will remain healthy because they regularly get a new lease on life. The option to recycle processes is available in worker process isolation mode. Figure 6 shows the Recycling configuration property sheet. Figure 6 Recycling Properties You can restart applications based on elapsed time, number of requests served, scheduled times, memory usage, and even on demand. To recycle a worker process, WAS spins down the faulty worker process while it completes the processing of the remaining requests in the queue.
You configure the application to drain the requests at a specific time. While the process is winding down, WAS creates a replacement worker process for the same namespace group and starts the new worker process before the old worker process stops. It's like passing the baton in a relay race. As a result, service interruptions are minimized. Once the old process finishes processing the outstanding requests, it shuts down normally. If the old process takes too long shutting down perhaps it's hanging , IIS will terminate it directly.
In addition to recycling processes automatically to maintain the integrity of a Web application, you may also configure IIS 6. For example, you can configure an application pool to ping the worker process periodically to make sure it's alive.
You may also configure an application pool to disable itself after a specific worker process crashes a configured number of times in a defined time limit. Finally, you can put time-outs on the worker process startup and shutdown periods. Figure 7 shows the property page for configuring the application pool health properties. Figure 7 Application Pool Properties. In addition to setting up health and recycling parameters, IIS features several tweakable performance parameters.
For example, if a specific application pool remains idle for a while, it makes no sense to keep it running and eating clock cycles. IIS lets you specify an idle time and will shut down an application pool's worker process after it remains idle for a specific period of time. You can also limit the number of requests that may be queued up, and you can configure how often the CPU counters are refreshed. Finally, you may specify the number of worker processes that can run in a Web garden where several instances of an app are running at once.
Figure 8 shows the Performance property sheet for an application. Figure 8 Performance Properties. There is a particular case in which you cannot use IIS 6. If it does, then you should run it under IIS 5. Choosing an execution mode in IIS 6. Running your Web site using worker process isolation mode provides application pooling, automated restarts, and debugging.
You'll probably want to use worker process isolation mode unless you find a conflict with an existing application. When your Web site requires SSL, you'll get security at the expense of performance because of the number of clock cycles used to encrypt the content.
Fortunately, there are some hardware-based accelerator cards that allow you to move some of this processing to the hardware. One place where security attacks can succeed is within components running as LocalSystem. Any opening in such a piece of software like a buffer overrun can let the attacker completely take over the machine on which it is running. IIS lets you configure the account under which an application's worker process or processes work, thereby controlling access to system resources.
Finally, IIS lets you restrict the extensions of the files you send to users. A metabase property allows you to send out only files with known extensions, while unknown file extensions receive an "access denied" error. Finally, there's a potpourri of new features in IIS to make the Web developer's life easier.
ASP can now deal with any file name using the Unicode filename string. Finally, through a feature called VectorSend, IIS supports the transmission of ordered lists of buffers and file handles. This way, IIS doesn't have to do buffer reconstruction or multiple write clients. Clearly, the platform of choice for the foreseeable future is the Internet. With so many users on the Internet every day, and with so many new applications on the way, the world's Web servers will certainly experience an increase in demand.
Its far-reaching improvements enhance performance, reliability, and scalability, and secure a spot for IIS 6. NET platform as computing platforms for the millennium. For background information see: Internet Information Services Features.
Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. The Internet has seen the growth of e-commerce, B2B business, collaboration, streaming and other new media, and these new applications require new features to meet increasingly complex needs. This article outlines the features in the upcoming version 6. Features such as Remote administration, caching, and metabase improvements, as well as custom isolation and security enhancements, make IIS 6.
The Current Web Climate State-of-the-art Web sites have quickly evolved from glorified electronic brochures to fully interactive customer order-entry sites, online media dispensers, data collection vehicles, and invaluable research tools. Distributed Administration Options At one time, it might have been possible to run your entire Web site from one box.
Metabase Improvements When Web developers and administrators manage a site, they configure such items as the directory structure used by the application, the executable modules mapped to certain file extensions, the pages shown for different errors, and the way security is managed. In moving the format of the metabase from a binary file to an XML file, IIS gains several distinct advantages over older versions: It's easier to diagnose and repair a corrupted metabase because it's represented in a human-readable format.
The metabase files can be read and saved directly using standard text editor tools though you normally won't want to edit it by hand unless you really know what you're doing—just like the Registry in that respect. The XML metabase has improved performance and scalability.
It has faster read times on Web server startup than the IIS 5.
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