Final Version • Issued July 28, 2008

Content creation continues to grow to meet consumer interest in on-demand and portable media delivery. New independent podcasters and vidcasters come online every day; traditional media companies begin to offer their content in downloadable formats; and new media publishers and aggregators continue to enter the market. Marketers see a greenfield opportunity to reach consumers in this burgeoning industry.

In order to support comparable reporting of audience traffic, measurement guidelines must be created. Advertising media buyers need confidence in the metrics to include portable media in their mix. The ADM is focused on creating standards and guidelines to support the continued and increasing monetization of downloadable media. These guidelines provide a set of specific and vetted measurement methods and techniques that are supported across the industry both by sellers and buyers of portable media.

A standard set of filters is necessary for analysis and accurate reporting of downloaded content. Audience or traffic reporting that is not analyzed with a certain set of filters can be astronomically inflated, resulting in unrealistic and unsubstantial measurements that overstate audience numbers. Therefore, the Association for Downloadable Media recognizes two methods of download measurement: Native Server Measurement and Third Party Measurement.

In order to comply with these guidelines, publishers would clearly state their download measurement methodologies thereby achieving high levels of confidence to buyers. Buyers seeking to work with ADM-compliant publishers would be entitled to request and receive these download methodologies. The goal is to achieve high levels of confidence around the metrics for both parties.

Native Server Measurement (NSM)
The Native Server is the actual end point where the media is hosted. Native Server Measurement refers to the log files derived from the Native Server. It may include the amount of data that was transferred in each log entry, and therefore may provide information to derive more than simple download statistics.

Third Party Measurement (TPM)
A Third Party server is the intermediary between the Native Server and another Third Party Server. Third Party Measurement refers to the files measuring the initial download requests as received by a third party server to be delivered to the requester. Because the Third Party server is a constant, it may uniformly measure download statistics across multiple hosting services.

Both types of measurement require analysis to measure downloads. These analytic techniques are used to determine the validity of each log file entry and report on actual downloads (versus duplicated or aborted download attempts for any number of reasons).

Below is a breakdown of the data collected and analytic factors used for download measurement.

Data Contained in Log Files

Log Files from Native Server

Data logged by native servers include request information about the media being downloaded as well as the amount of bytes transferred during the download transaction. Each logged entry may contain the following data.

• IP Address – Unique Internet address of the user consuming the media file.
• Time Stamp – Time at which the request was made for the media file.
• Request – The request specifies the media file requested and provides the method at which the request should be handled.
• HTTP Status Code – A technical code defined by the HTTP protocol that determines the status of the request.
• Referrer – Location where the request came from.
• User Agent – A unique value that identifies the service or application making the request. e.g. web browser such as Internet Explorer, podcatching agent such as iTunes, a web bot such as Google.
• Byte Range – This is the range of start and end bytes requested by the media consumer.
• Bytes Served – This is the amount of bytes that have been transferred to the media consumer in a given request. Depending on the type of request made, the bytes served may be less than or equal to the size of media file.

Log Files from Third Party Server

Data logged by third party servers include request information about the media being downloaded. Each logged entry may contain the following data.

• IP Address – Unique Internet address of the user consuming the media file.
• Time Stamp – Time at which the request was made for the media file.
• Request – The request specifies the media file requested and provides the method at which the request should be handled.
• HTTP Status Code – A technical code defined by the HTTP protocol that determines the status of the request.
• Referrer – Location where the request came from.
• User Agent – A unique value that identifies the service or application making the request. e.g. web browser such as Internet Explorer, podcatching agent such as iTunes, a web bot such as Google.
• Byte Range – This is the range of start and end bytes requested by the media consumer.

The data contained in either native or third party server log files does not necessarily mean that the data is analyzed. The method of analysis used varies.

Analysis Techniques and Factors

There are a number of factors used in any given technique to analyze log files. These techniques can be combined to create a very powerful set of download metrics. Recognized as the core factor of analysis, the IP Address must be included in any technique in order to comply with these guidelines.

• IP Address – The IP address is used to determine if the request is unique or a duplicate. It may also be used to determine geographical information of the media consumer.
• Time Stamp – The date and time may be used to determine if the request should be counted.
• HTTP Status Code – The appropriate HTTP status code is examined to determine if the request should be counted.
• Bytes Served – The value may be used to determine if the media was completely downloaded. (Note: This information is only available from native server log files.)
• Referrer – The origin of the download may be used to determine if the request should be counted. e.g. media that is auto played upon loading a web page may be removed or reported.
• User Agent – The identifier of the application or service consuming the media may be analyzed to determine if the request is unique.
• Byte Range – The range of bytes requested in a given request may be used to determine what portion of the media is requested. When analyzed across multiple requests, the information may provide an accurate assessment to determine if the media was completely downloaded.