Knowledge Center > Tutorials

Unlike dynamic files, static files do not change on a regular basis. Updated content in a static file can signal an intentional revision, an unauthorized change, a major development of which you may need to be aware, or even the removal of the resource from the server.

ipMonitor's HTTP - QA and FTP - QA Monitors can check for modifications made to a static webpage or FTP resource, and alert you as soon as a change is detected.

After completing this tutorial, you will know:

• How to configure the HTTP - QA and FTP - QA Monitors to watch for changes in a static file
• How the HTTP - QA and FTP - QA Monitors detect file changes
• How to minimize bandwidth consumption
• How to set the Monitor timing parameters to eliminate false Alerts

If you use web analytics or log analysis software, the HTTP - QA and FTP - QA Monitors may cause hits to be generated. Refer to your log analysis software for information regarding how to exclude ipMonitor traffic from analysis.

If your web or FTP server requires authentication, you will need to create a new Credential for use with the HTTP - QA or FTP - QA Monitor. You can do this ahead of time by using the Credentials Manager, or you can use the Credentials Wizard during the Monitor Configuration stage. For more information, refer to the Credentials section of ipMonitor's Context-Sensitive Help system. The Context-Sensitive Help can be accessed by clicking the Help link located in the top right corner of the Administration web interface.

Click the PDF icon to open a printable PDF version of this tutorial. It includes all the information found here, including images from the ipMonitor software, diagrams, and links to additional resources.

Note: Both the HTTP - QA and the FTP - QA Monitors follow the same configuration scheme. Although the images in the example below depict the setup procedure for the HTTP - QA Monitor, the following instructions can also be applied to the FTP - QA Monitor.

1. Click the Monitors menu option and then click Add a Monitor. Choose the FTP - QA or HTTP - QA Monitor from the Multi-Transaction / QA category.

2. Enter a unique, descriptive name for the Monitor in the Name field.
3. Choose whether to automatically add the new Monitor to a particular Group.
4. Check the Enabled checkbox.
5. Choose whether you want the Monitor to Store Monitor Statistics for Recent Activity and Historical Reports.

6. Specify the location of the server you want to monitor. Both IP Address and Domain Name are valid entries.
7. Specify the Port Number that the target website or FTP server responds on. By default, the standard Port used by HTTP servers (Port 80) is already entered for the HTTP - QA Monitor, and the standard Port used by FTP servers (Port 21) is entered for the FTP - QA Monitor.
8. Enter the relative path to the resource being monitored.

TIP This field must begin with a forward slash (/). Examples of valid relative paths are: / /index.asp /notes/changelog.txt

9. If your server requires authentication, you must create and apply a Credential. Click the 'Select...' button to launch the Credentials Wizard.

TIP The FTP - QA Monitor supports the ability to automatically log in to an anonymous FTP server. To use this ability, do not select a Credential for Monitoring. The following login parameters are provided by ipMonitor: USER NAME = anonymous PASSWORD = ipmonitor7@ipmonitor.com

10. Enable the Force communication through an HTTP Proxy Server checkbox to force ipMonitor to monitor HTTP resources through your organization's HTTP Proxy Server.
    
    Before you select this option, first ensure ipMonitor's global Client HTTP Settings have been correctly set up to permit communications with your proxy server.
    
    Note: Refer to the Server Settings section for more information.

11. Click the Update... button to obtain a checksum (CRC-32) of the resource using the Test Parameters provided above.

TIP If the resource is modified, ipMonitor will need to obtain a new checksum for comparison. The new sample can be obtained by clicking the Update... button at any time.

ipMonitor does not maintain a local copy of the resource being monitored. When the Update... button is clicked, the resource is sampled to obtain the checksum (CRC-32).

A checksum (also referred to as a 'hash') is a type of cyclic redundancy check (CRC). It results from using a mathematical algorithm to compress a block of data into a small number of bits. A CRC-32 converts the data into a fixed-length (32 bit) string.

The above diagram shows that the HTTP - QA and FTP - QA Monitors detect changes in a static file by:

1. Retrieving the monitored resource.
2. Generating a checksum based on the retrieved file.
3. Comparing the checksum against the original value.

Note: If the file size or checksum of the monitored resource is different than the original value, ipMonitor will begin the failure and alerting process.

The HTTP - QA and FTP - QA Monitors can generate considerable bandwidth if aggressive timing parameters are applied. Depending on the size of the file being monitored, if the defined timing parameters require the Monitor to frequently retrieve the resource, bandwidth consumption can quickly become a concern.

Note: The following suggested parameters are intended to be used with resources that are expected to change very infrequently, or not at all. For example, downloadable resources such as PDF documents and executable files.

• Setting the Maximum Test Duration, as well as the Delays Between Tests While: Up, Warn, Down, Lost fields to 28800 seconds will result in the Monitor requesting the file three times a day (every eight hours).
• Setting the Accumulated Failures per Alert field to 1 will result in an Alert being sent as soon as the Monitor detects a change in the resource.
• Setting the Maximum Alerts to Send field to 1 will result in only one Alert being sent before the Monitor enters a Lost state.

TIP Ensure that the Monitor is assigned to a Profile, and that Alerts have been configured for that Profile. Otherwise, the Monitor will be unable to generate an Alert when a failure occurs.

In addition to bandwidth considerations, the length of time required to download the target file must also be taken into account when setting timing parameters.

If the time period specified in the Maximum Test Duration field is less than the length of time it would take the HTTP - QA or FTP - QA Monitor to download the resource, the test will fail, triggering any configured Alerts.

• File size: 4 MB
• Download speed: 128 kbps
• Estimated download time: 4 minutes

The Maximum Test Duration field should be set to at least 240 seconds. We recommend increasing the minimum required time period to ensure that the timing parameter is flexible enough to account for heightened network traffic and other causes of increased download times.

For more information regarding the HTTP - QA and FTP - QA Monitors, refer to the Monitors section of the Context-Sensitive Help system. Click Monitor Types, then select HTTP - QA or FTP - QA. The Context-Sensitive Help can be accessed by clicking the Help link located in the top right corner of ipMonitor's Administration web interface.

For information on other features and concepts related to those discussed in this article, refer to the following ipMonitor resources:

< Back

Last Updated: April 3, 2006 | What did you think of this topic?