This page collects the results of an informal survey of implementations’ approaches to MTU matters. It captures what default size an implementation picks to start, whether they support (DPL)PMTUD, and whether they advertise a max_udp_payload_size to their peer. Many implementations support configurability of these options, so the values may not represent any specific deployment.

Implementation Default start packet size (DPL)PMTUD supported Default max_udp_payload_size
google quiche 1250 No -
MsQuic 1240 Yes Based on MTU of the socket/interface
mvfst 1232 No (experimented with and subsequently removed) -
neqo 1200 Yes -
ngtcp2 1200 Yes -
pico-quic 1252 (IPv4), 1232 (IPv6) Yes 1440
quinn 1200 Yes -
quiche 1200 Yes -
s2n-quic 1200 Yes -

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