ngtcp2 — Datagrams arriving from a second server address

Pass

Tolerated it and continued. The specification permits this but does not require it; a client that rejected it would also be conformant.

The client did what the clause requires.

What was measured

Client

ngtcp2 — ngtcp2 + nghttp3 (direct), 3c23148

Test

Datagrams arriving from a second server address — q-connection-migration

Clause

RFC 9000 §9.6 (SHOULD)

Class

discretionary — The RFC permits either behaviour; the report says which was chosen.

Required behaviour

Keep using the address you are already talking to. §9.6 says a client "SHOULD ignore packets received from a server address other than the one it is currently using for sending packets" — a SHOULD, so quietly discarding them and objecting are both conformant. Following the new address is not: nothing is listening there, and a server may only move a client to an address it advertised as its preferred one.

Measured

2026-09-18

Reproduce it

The suite is the judge, so the reproduction is to point the same client at the same test and let the server report what it saw.

SESSION=$(curl -sX POST https://conformance.pqcrypta.com/session | jq -r .id)
# then drive ngtcp2 at the test URL and read the verdict:
curl -s https://conformance.pqcrypta.com/report/$SESSION.json | jq '.results["q-connection-migration"]'