Re: [quicwg/base-drafts] ICID or OCID? (#2926)

[Mike Bishop <[e-mail]>]

Two different things, but you're probably right that they should both be explicitly defined:

- The "Original destination connection ID" is the DCID used in the client's very first Initial packet.  If the server responded with a Retry, the server needs to:
    - include the ODCID in the Retry packet to verify the Retry packet came from something on-path
    - include the ODCID in the eventual handshake's transport parameters to verify that the Retry packet originated from the server or something cooperating with it, not a MITM
- The "Initial connection ID" is the DCID used in the client's Initial packet to which the server responded with an Initial.  This CID determines the keys used for Initial packets throughout the handshake. (But see #2823.)  This CID might have been server-chosen (from a Retry) or client-chosen (no Retry).

If there's no Retry packet, they refer to the same CID, but I don't think there's a reference to the ODCID outside the context of a Retry.

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