  In this paper, we study the potentials of passive measurements to gain
advanced knowledge about QUIC deployments. By analyzing one month backscatter
traffic of the /9 CAIDA network telescope, we are able to make the following
observations. First, we can identify different off-net deployments of
hypergiants, using packet features such as QUIC source connection IDs (SCID),
packet coalescence, and packet lengths. Second, Facebook and Google configure
significantly different retransmission timeouts and maximum number of
retransmissions. Third, SCIDs allow further insights into load balancer
deployments such as number of servers per load balancer. We bolster our results
by active measurements.
