Port migration question

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Ceyhun Atacan

Nov 10, 2022, 11:18:29 AM11/10/22
to proto...@chromium.org
Greetings all,
I have a question regarding what I suppose is a port migration case where a connection switches to a different client port. When the migration occurs, the client seems to use a DCID that's ever so slightly different from the original DCID.
For example, in the connection depicted below (a lenghthy YouTube session), the client DCID is c4b4fd09b581ede9 until the migration happens at frame# 101915 (client port changes from 50734 to 52158). The DCID seems to change to c5b4fd09b581ede9 for the next 2 packets (frame#101915 and 101919). And then the client seems to start using c4b4fd09b581ede9 again, starting at frame #101922.
I looked into the connection migration part of the QUIC RFC but I think I'm missing something about that bit in that second byte of the payload. I keep assuming it to be the first byte of the DCID but there's probably something else going on.
I'd appreciate it if anyone could point me to some resources to understand this behaviour.



Ceyhun Atacan

Nov 10, 2022, 11:30:00 AM11/10/22
to proto...@chromium.org
Ugh..Please disregard the "switching back to using the old DCID at frame #101922" part. It's just a packet from the original connection.
It seems we're switching to a new client port with a new DCID.
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