Web consumers are getting smarter and installing ad blockers. These ad blockers prevent third party content from appearing on the visited website. Ad blockers can decrease the number of http requests and total downloaded bytes, improving web performance for end users.
Catchpoint has a matched pair of last-mile nodes to monitor page performance with and without an ad blocker. The node names are LM-Adblock ON and LM-Adblock OFF. Both nodes are on the internet service provider Time Warner, Los Angeles. The ad blocker that is used is called Pi-Hole.
Pi-Hole is an ad blocking software/hardware solution which acts as a DNS server and resolver. It has 1.6 million ad server domains stored. If one of these domains is requested, the request is redirected to the Pi instead of the actual server. Ads will show an IP address of the Pi server, 192.168.1.4. Since the ad content is not located on the Pi server, this ensures the ad server is never contacted, and prevents the download from the third party host, providing a 404 response in the waterfall:
Please note that relocating these third-party HTTP requests can affect the DNS, connect, wait, and response time metrics. On average each ad requests takes about 40 ms.
For more information on last-mile node testing and the effects of ad blocking, please read this article Understanding Last Mile Node Testing and Blog Ad-Blocking on Apple iOS9