Original text:
The value of the Destination Connection ID field from the first Initial packet sent by the client.  This transport parameter is <del> only sent by a server.  A server MUST include the original_connection_id transport parameter if it sent a Retry packet. </del>  The idle timeout is a value in milliseconds that is encoded as an integer; see (idle-timeout).  If this parameter is absent or zero opening.  If the transport parameter is absent, streams of that type start with a flow control limit of 0. <del> A client MUST NOT include an original connection ID, a stateless reset token, or a preferred address.  A server MUST treat receipt of any of these transport parameters as a connection error of type </del>  TRANSPORT_PARAMETER_ERROR. 19.

Reviewer comments:
Note that may want to change the phrasing of the ODCID field, depending on which PR lands first.
End of section 18, transport It seems the term is "initial connection ID" not "original connection ID", at least I can't find it defined anywhere in transport.
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 .) 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.
I think that we already concluded this in .
This is a separate issue, about definition of these terms; is about whether these need to be separate concepts depending on the outcome of other issues. NAME notes that the term "original connection ID" appears only to say that a client MUST NOT send one, and that literal string appears nowhere else in the document except the changelog. This refers to the transport parameter , whose definition matches the description of the "Original Destination Connection ID" field in Retry and references Retry, but doesn't use that term. I'd suggest using the names of the prohibited TPs in stating the client restriction, and referencing the "Original Destination Connection ID" field by name from the TP definition.

Revised text:
The value of the Destination Connection ID field from the first Initial packet sent by the client.  This transport parameter is  <ins> only sent by a server.  This is the same value sent in the "Original Destination Connection ID" field of a Retry packet (see packet-retry).  A server MUST include the original_connection_id transport parameter if it sent a Retry packet. </ins> The idle timeout is a value in milliseconds that is encoded as an integer; see (idle-timeout).  If this parameter is absent or zero opening.  If the transport parameter is absent, streams of that type start with a flow control limit of 0.  <ins> A client MUST NOT include server-only transport parameters (original_connection_id, stateless_reset_token, or preferred_address).  A server MUST treat receipt of any of these transport parameters as a connection error of type </ins> TRANSPORT_PARAMETER_ERROR. 19.