On Tue, 21 Dec 2021 at 08:11, Hank Nussbacher <hank@interall.co.il> wrote:
Out of curiosity - does anyone know why Google is truncating ICMP responses ?
As Google has stated in many forums and I quote: "Google Public DNS is a Domain Name System service, not an ICMP network testing service."
The core issue is that many watchdogs implemented in all kinds of devices use ICMP for health checking (and just one host), as opposed to DNS or HTTP services of multiple hosts. Those users have to point their watchdogs somewhere, and "ping.crappy-iot-vendor.com" just sounds less reliable (and probably is), then one of those quad8. quad1 or quad9 services. It's obvious that it's not a DNS Servers job to respond to ICMP requests, and under DoS they'd probably rate-limit it. I think Google choice makes sense, at least it does not allow 1:1 reflection at big sizes. Nobody is interested in running reliable anycast ICMP responders on the internet, after all, no useful data can be collected with it. Device vendors will keep shipping code with watchdogs that can only ping a single host, so users will keep putting DNS servers in there. Lukas