Web censorship measurements of HTTP/3 over QUIC

In China (AS45090), HTTP/3 over QUIC has a lower overall failure rate (27.1%) than HTTPS over TCP (37.3%), but hosts that time out during the TCP handshake (TCP-hs-to, indicating IP blocking) always also fail over QUIC — while hosts blocked via TLS-hs-to or conn-reset (SNI-based methods) nearly always succeed over QUIC.

§5.1, Table 1, Figure 3a evaluation ip-blockingsni-blockinghttp3-quic-block cn

In India (AS55836), TCP and QUIC failure rates closely track each other (15.0% vs 12.0%), with every TCP-hs-to and route-err failure matched by a corresponding QUIC failure, confirming IP-based blocking affects both protocols equally. In contrast, India AS14061 (VPS) shows 16.3% TCP failure entirely from route-err but only 0.1% QUIC failure, suggesting the VPS vantage point sits outside the censored path.

§5.1, Table 1, Figure 3b detection ip-blockinghttp3-quic-block in

In Iran (AS62442), HTTPS connections fail at 34.4% (mostly TLS-hs-to, consistent with SNI filtering), while HTTP/3 over QUIC fails at only 16.2%. SNI spoofing reduces TCP failure from 60.1% to 10.2% but has zero effect on QUIC (20.1% both with real and spoofed SNI), indicating Iranian censors apply separate UDP endpoint blocking to QUIC rather than SNI-based identification.

§5.2, Table 3 detection sni-blockinghttp3-quic-blockport-blocking ir

Only approximately 5% of domains from the combined Citizen Lab and Tranco Top-4000 test lists supported QUIC in early 2021, heavily skewing the measurable set toward large global .com domains (e.g., Google properties). This bias means the study predominantly captures censorship of internationally targeted sites rather than country-specific domains.

§4.3 evaluation http3-quic-blockmeasurement-platform cnirinkz

Across all four studied countries (China, Iran, India, Kazakhstan), HTTP/3 over QUIC had consistently lower failure rates than HTTPS over TCP: 27.1% vs 37.3% in China, 16.2% vs 34.4% in Iran, and 12.0% vs 15.0% in India (AS55836). The only QUIC-specific interference method observed was black-holing during the QUIC handshake (QUIC-hs-to); no RST injection or SNI-based QUIC filtering was detected.

§5, Table 1 evaluation http3-quic-blockip-blocking cnirinkz