WAN Performance and Kerberos Authentication with SharePoint

Written By: Knox Cameron -- 12/2/2010 -- join -- contribute -- (2962) comments -- printer friendly version

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Categories: Configurations, IIS, Infrastructure, MOSS 2007, System Administration, WSS3

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You implement Kerberos authentication but SharePoint becomes slower, particularly for remote users.


Kerberos is more efficient for the server, but it can increase traffic between the browser and the server, making your site slower for users. Use a tool like Fiddler to see what is actually happening behind the scenes, and configure IIS to reduce the traffic and make the site faster.

SharePoint page load performance

A while ago, I was involved in troubleshooting performance issues for a global Intranet built using MOSS 2007 on Windows Server 2003 SP2. Users were complaining about how slowly pages loaded. Unfortunately, this is a common issue with SharePoint.

SharePoint is a system with a wide range of capabilities for collaboration and content publishing, as well as being a powerful application platform. Inevitably, this power comes with a price - the need to transmit and receive more data from the browser which will make it slower to use than an old-fashioned html web site. Page load performance can be a real barrier to use, and it is worth making the effort to make it as fast as possible given your circumstances.

There are software and hardware acceleration solutions on the market, some of which are quite effective. However, even without going down the route of add-on products, there are often ways of significantly improving performance by simple (or not so simple) configuration changes.

This tip describes how we investigated the performance problem, one of the issues we uncovered, and how we fixed it. While you may not face this specific issue, the approach can be useful for identifying and fixing the issues in your environment.

Monitoring traffic

The first step in fixing any problem is to understand it. We knew page loads were slow, but we needed to understand why. For this, we needed a way of seeing exactly what requests were going from the browser to the server and what was coming back.

There are a number of different ways of doing this, including utilities like NetMon. However, we decided to use a utility called Fiddler, because it is free, easy to install and easy to use. Fiddler is an unsupported "PowerToy" from Microsoft, but it actually works well with either Internet Explorer or FireFox on the client.

When you run Fiddler, it acts as a proxy on your computer, intercepting traffic between your browser and the web server. By default, it just captures http, but you can configure it to capture https as well (see its documentation for how to do this). Here, I browsed the home page of with Fiddler capturing the requests. I selected the requests from the session list on the left, and selected the Statistics tab on the right, with the chart showing response types.

Fiddler screenshot

Select the "Timeline" tab on the right to see a "waterfall" chart of the requests and responses. I also collapsed the session list on the left.

Waterfall chart

Notice how the page took about two and a half seconds to load, and that most JavaScript, stylesheets and images took about another second. Some other resources took significantly longer, but the browser will generally display the page without waiting for all the resources, and just add them in when they arrive. The "diskette" icon indicates a resource where the server returned a 304 response telling the browser to use its cached copy.

Notice how the bars are hatched. This indicates that Fiddler is using "buffering mode", where it captures responses from the server before passing them on to the browser. This allows you to configure Fiddler to modify the data, but can degrade performance compared to normal browsing. Since we are only interested in observing, click the Streaming button in the toolbar to make Fiddler pass through data as soon as it is received.

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