You are required to request the resource file for any included impression tracking elements. The use of multiple impression elements enables the sharing of impression-tracking information with many ad serving systems, such as a vendor or partner ad server employed by the advertiser. When multiple impression elements are included in a VAST response, the publisher is required to request all impressions at the same time, or as close as possible to the same time. Any significant delay between impression requests may result in count discrepancies between ad serving systems.
Each of these elements contains a reference to a server-side resource, which historically has been a 1x1 pixel image but may also be a script or document reference, although you are not required to do anything with the response that is returned. In a Server-to-server environment, it is not possible to support an "Audio Ad Impression" as defined in the Impression Measurement Guidelines (the document does acknowledge the server-to-server case, but does not provide guidelines for impression reporting in that context). Triton Digital recommends firing the impression as close as possible to the opportunity to be played, ideally after the ad has buffered. Also, the following HTTP headers need to be provided:
X-Device-IP: set to the IP address of the device on whose behalf this request is being made.
X-Device-User-Agent: set to the User-Agent of the client on whose behalf the request is being made.
X-Device-IP and X-Device-User-Agent need to match the values you passed in the ad request.
Impression Delay
In order for the impression to be recorded, you must call the impression within the time defined in the expiry field of the ad response.
For TAP Programmatic, the maximum is 1680 seconds (28 minutes) unless defined as lower by the DSP. If not defined, then expiry is 1680 seconds.
For TAP, the maximum is 3600 seconds (60 minutes).