  QUIC is a performance-optimized secure transport protocol and a building
block of the upcoming HTTP/3 standard. To protect against denial-of-service
attacks, QUIC servers need to validate the IP addresses claimed by their
clients. So far, the QUIC protocol conducts address validation for each
hostname separately using validation tokens. In this work, we review this
practice and introduce a new QUIC transport parameter to allow a shared address
validation across hostnames. This parameter indicates to the client, that an
issued validation token can be used to abbreviate the address validation when
connecting to specific other hostnames. Based on trust-relations between
real-world hostnames we evaluate the performance benefits of our proposal. Our
results suggest that a shared address validation saves a round-trip time on
almost 60% of the required handshakes to different hosts during the first
loading of an average website. Assuming a typical transatlantic connection with
a round-trip time of 90ms. We find that deploying our proposal reduces the
delay overhead to establish all required connections for an average website by
142.2ms.
