What service is used to serve the same ad in multiple locations on a single page load?
It appears in this example Google is serving the ads, however I don't see an option for this in Google Adsense.
Questions on Web Applications Stack Exchange are expected to relate to web applications within the scope defined in the FAQ. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about closed questions here.
It sometimes happens in AdSense by chance, but the publisher cannot control it. Well ordinary AdSense publishers cannot - I don't know if it's possible for the premium account folks, who have a lot more options.
And sorry, but I don't know any services that offer multiple ad-units from the same campaign per page.