Packet Clearing House (PCH) is the international organization charged with providing operational support and security to critical Internet infrastructure, including Internet exchange points and the core of the domain name system. In the fulfillment of these responsibilities, we operate public looking-glasses and routing data-collection facilities at approximately a third of the world’s public Internet Exchange Points (IXPs). We also operate the world’s largest anycast DNS network, hosting three of the DNS root letters, and more than 400 top-level domains. While the traffic normally generated by each of these services is small, each provides a unique and necessary service to the Internet infrastructure community and their criticality requires that we provision each with sufficient interconnection bandwidth to protect them against distributed denial of services (DDoS) attacks.

https://www.pch.net/about/peering

https://en.wikipedia.org/wiki/Root_name_server