Hi Thomas and other authors,
Thank you for responding to all of our questions! We have updated the document
accordingly.
Note that we updated Figure 5 per your response to our question #10; please
review the TXT output (ascii-art) and the HTML/PDF outputs (svg) to make sure
that the figure appears as desired.
Also, regarding these questions:
> We hava couple of questions re: RFC8446bis and RFC8447bis references.
>
> We make normative references to RFC8446 and RFC8447.
>
> Their "bis" documents are:
> - draft-ietf-tls-rfc8447bis (PUB as RFC 9847)
> - draft-ietf-tls-rfc8446bis (currently in AUTH48, to become RFC 9846)
>
> These documents are in the same publication cluster (C430) as RRC, and
> respectively update and obsolete their counterparts.
>
> Two questions:
> 1. Should the references in RRC be updated (at least, RFC8447 to RFC9847)?
> 2. Should RRC wait for RFC-to-be 9846 to be published?
For #1, we did update instances of [I-D.ietf-tls-rfc8447bis] in the original to
[RFC9847]. The only instance of [RFC8447] is in following sentence. Would you
like to remove the reference to RFC 8447 here and only cite RFC 9847?
Current:
Recommended:
Indication of whether the message is recommended for
implementations to support. The semantics for this field is
defined in Section 5 of [RFC8447] and updated in Section 3 of
[RFC9847].
Perhaps:
Recommended:
Indication of whether the message is recommended for
implementations to support. The semantics for this field is
defined in Section 3 of [RFC9847].
For #2, note that RFC-to-be 9846 has been in AUTH48 for over two months, and
the author is working through some issues that may take additional time (see
https://www.rfc-editor.org/auth48/rfc9846). The decision to either 1) keep the
reference to [RFC8446] in this document or 2) update to [RFC9846] and wait to
publish together is up to you as authors. The document shepherd and AD may also
provide input. Please let us know how you would like to proceed.
FILES (please refresh):
Updated XML file:
https://www.rfc-editor.org/authors/rfc9853.xml
Updated output files:
https://www.rfc-editor.org/authors/rfc9853.txt
https://www.rfc-editor.org/authors/rfc9853.pdf
https://www.rfc-editor.org/authors/rfc9853.html
Diff files showing all changes made during AUTH48:
https://www.rfc-editor.org/authors/rfc9853-auth48diff.html
https://www.rfc-editor.org/authors/rfc9853-auth48rfcdiff.html (side by side)
Diff files showing all changes:
https://www.rfc-editor.org/authors/rfc9853-diff.html
https://www.rfc-editor.org/authors/rfc9853-rfcdiff.html (side by side)
https://www.rfc-editor.org/authors/rfc9853-alt-diff.html (diff showing
changes where text is moved or deleted)
For the AUTH48 status of this document, please see:
https://www.rfc-editor.org/auth48/rfc9853
Thank you,
Rebecca VanRheenen
RFC Production Center
> On Feb 20, 2026, at 4:44 AM, Thomas Fossati <[email protected]> wrote:
>
> Dear Rebecca and Sandy,
>
> Authors,
>
> On Fri, 13 Feb 2026 at 18:56, <[email protected]> wrote:
>> While reviewing this document during AUTH48, please resolve (as necessary)
>> the following questions, which are also in the source file.
>>
>> 1) <!-- [rfced] Because this document updates RFC 9147, please
>> review the errata reported for RFC 9147
>> (https://www.rfc-editor.org/errata/rfc9147)
>> and let us know if you confirm our opinion that none of them
>> are relevant to the content of this document.
>> -->
>
> Confirmed.
>
>> 2) <!-- [rfced] Please note that the title of the document has been updated
>> as follows.
>>
>> Original:
>> Return Routability Check for DTLS 1.2 and DTLS 1.3
>>
>> Current:
>> Return Routability Check for DTLS 1.2 and 1.3
>> -->
>
> OK
>
>
>> 3) <!-- [rfced] Is this sentence in the abstract correct as is, or should
>> it include the word "subprotocol" (which is used in a similar sentence in
>> the Introduction)?
>>
>> Original:
>> This document specifies a return routability check for use in context
>> of the Connection ID (CID) construct for the Datagram Transport Layer
>> Security (DTLS) protocol versions 1.2 and 1.3.
>>
>> Current:
>> This document specifies a Return Routability Check (RRC) for use in
>> the context of the Connection ID (CID) construct for the Datagram
>> Transport Layer Security (DTLS) protocol versions 1.2 and 1.3.
>>
>> Perhaps:
>> This document specifies a Return Routability Check (RRC) subprotocol for
>> use in the context of the Connection ID (CID) construct for the Datagram
>> Transport Layer Security (DTLS) protocol versions 1.2 and 1.3.
>> -->
>
> Both Current and Perhaps are correct.
> Perhaps the "Perhaps" is slightly better.
>
>> 4) <!-- [rfced] Should "return routability check" here be updated to "basic
>> return routability check" in these instances in Section 5.2?
>>
>> Original:
>> * When a return_routability_check message of type path_drop was
>> received, the initiator MUST perform a return routability
>> check on the observed new address, as described in
>> Section 5.1.
>> ...
>> 5. If T expires the peer address binding is not updated. In this
>> case, the initiator MUST perform a return routability check on
>> the observed new address, as described in Section 5.1.
>>
>> Perhaps:
>> * When a return_routability_check message of type path_drop was
>> received, the initiator MUST perform a basic return routability
>> check on the observed new address, as described in
>> Section 5.1.
>> ...
>> 5. If T expires the peer address binding is not updated. In this
>> case, the initiator MUST perform a basic return routability check on
>> the observed new address, as described in Section 5.1.
>> -->
>
>
> OK
>
>> 5) <!-- [rfced] For clarity, may we update "cater for"?
>>
>> Original:
>> * The initiator MAY send multiple return_routability_check messages
>> of type path_challenge to cater for packet loss on the probed
>> path.
>>
>> ...
>>
>> Note that RRC does not cater for PMTU discovery on the reverse path.
>>
>>
>> Perhaps:
>> * The initiator MAY send multiple return_routability_check messages
>> of type path_challenge to account for packet loss on the probed
>> path.
>>
>> ...
>>
>> Note that RRC does not account for PMTU discovery on the reverse path.
>> -->
>
> OK
>
>> 6) <!-- [rfced] We see the following phrasing with the message types
>> defined in this document (i.e., path_challenge, path_response, and
>> path_drop). Please review and let us know if any updates are needed for
>> consistency.
>>
>> return_routability_check message of type path_response
>> return_routability_check message of type path_challenge
>> return_routability_check message of type path_drop
>>
>> path_challenge message
>> path_response message
>> path_drop message
>>
>> path_challenge
>> path_response
>> path_drop
>>
>> Some examples:
>> 3. The peer (i.e., the responder) cryptographically verifies the
>> received return_routability_check message of type path_challenge
>> and responds by echoing the cookie value in a
>> return_routability_check message of type path_response.
>> ...
>> Each path_challenge message MUST contain random data.
>> ...
>> * The responder MUST send the path_response or the path_drop to the
>> address from which the corresponding path_challenge was received.
>> ...
>> -->
>
> These are all correct and consistent with the surrounding context.
>
>> 7) <!-- [rfced] Please review "use padding using...up to". Would updating
>> as follows improve readability of this sentence?
>>
>> Original:
>> * The initiator MAY use padding using the record padding mechanism
>> available in DTLS 1.3 (and in DTLS 1.2, when CID is enabled on the
>> sending direction) up to the anti-amplification limit to probe if
>> the path MTU (PMTU) for the new path is still acceptable.
>>
>> Perhaps:
>> * The initiator MAY use the record padding mechanism
>> available in DTLS 1.3 (and in DTLS 1.2, when CID is enabled on the
>> sending direction) to add padding up to the anti-amplification limit
>> to probe if the Path MTU (PMTU) for the new path is still acceptable.
>> -->
>
> Your proposal is correct and reads much better.
>
>> 8) <!-- [rfced] FYI - We updated "1s" to "1 second" for clarity.
>>
>> Original:
>> If an implementation has no way to obtain information regarding the
>> RTT of the active path, T SHOULD be set to 1s.
>>
>> Perhaps:
>> If an implementation has no way to obtain information regarding the
>> RTT of the active path, T SHOULD be set to 1 second.
>> -->
>
> OK
>
>> 9) <!-- [rfced] How may we clarify this sentence, especially "increasing
>> capabilities" and the text starting with "partly following
>> terminology..."?
>>
>> Original:
>> Two classes of attackers are considered, off-path and on-path, with
>> increasing capabilities (see Figure 4) partly following terminology
>> introduced in QUIC (Section 21.1 of [RFC9000]):
>>
>> Perhaps:
>> This model includes two classes of attackers, off-path and on-path, with
>> various capabilities (see Figure 4). The following
>> descriptions of these attackers are based on those
>> introduced in QUIC (Section 21.1 of [RFC9000]):
>> -->
>
> Using "various" instead of "increasing" is not wrong, but drops some
> of the intended semantics.
>
> OK for "based on those" instead of "partly following terminology".
>
>> 10) <!-- [rfced] Please review the use of "(1)" in the sentences below.
>> Figure 5 does not include a "1". Should "1" be removed from these sentences
>> or added to Figure 5? Or does "(1)" in these sentences refer to Figure 6?
>> Let us know how to clarify. Also, should "timeout of (1)" be updated to
>> "timeout of the path_challenge message (1)"?
>>
>> Original:
>> Figure 5 illustrates the case where a receiver receives a packet with
>> a new source address. In order to determine that this path change
>> was not triggered by an off-path attacker, the receiver will send an
>> RRC message of type path_challenge (1) on the old path.
>>
>> <Figure 5>
>>
>> Case 1: The old path is dead (e.g., due to a NAT rebinding), which
>> leads to a timeout of (1).
>>
>> As shown in Figure 6, a path_challenge (2) needs to be sent on the
>> new path. If the sender replies with a path_response on the new path
>> (3), the switch to the new path is considered legitimate.
>>
>> <Figure 6>
>> -->
>
> Good catch, thanks!
>
> We should edit Figure 5 to include the message number and an arrow, like this:
>
> ~~~ aasvg
> new old
> path .----------. path
> | |
> .-----+ Receiver +-----.
> | | | |
> | '----------' |
> | 1
> | |
> | |
> .----+------. v
> / Attacker? / |
> '------+----' |
> | |
> | |
> | |
> | .----------. |
> | | | |
> '-----+ Sender +-----'
> | |
> '----------'
> ~~~~
>
>> 11) <!-- [rfced] Would it be helpful to update "path_challenge" here to
>> "path_challenge (1)"?
>>
>> Original:
>> The receiver sends a path_challenge on the old
>> path and the sender replies with a path_response (2) on the old path.
>> The interaction is shown in Figure 8.
>>
>> Perhaps:
>> As shown in Figure 8, the receiver sends a
>> path_challenge (1) on the old path, and the sender replies with a
>> path_response (2) on the old path.
>> -->
>
> Yes, please.
>
>> 12) <!-- [rfced] Font styling
>>
>> a) The terms enclosed in <tt> in this document are listed below. Please
>> review to ensure the usage of <tt> is correct and consistent. Let us know
>> if any updates are needed. Note that <tt> produces fixed-width font in the
>> HTML and PDF outputs but no changes in the TXT output.
>>
>> <tt>connection_id</tt>
>> <tt>extension_data</tt>
>> <tt>extension_type</tt>
>> <tt>msg_type</tt>
>> <tt>path_challenge</tt>
>> <tt>path_drop</tt>
>> <tt>path_response</tt>
>> <tt>return_routability_check</tt>
>> <tt>rrc</tt>
>> <tt>tls12_cid</tt>
>>
>>
>> b) The following sentence includes <em>, which produces underscores in the
>> TXT output and italics in the HTML and PDF outputs. Please review to ensure
>> that this is a correct use of <em>.
>>
>> Original:
>> To prevent this, RRC cookies
>> must be _freshly_ generated using a reliable source of entropy
>> [RFC4086].
>> -->
>
> Both a) and b) look good.
>
>> 13) <!-- [rfced] Please review the "type" attribute of the sourcecode
>> element in Section 4, as "tls-msg" is not part of the current list of
>> preferred values
>> (https://www.rfc-editor.org/rpc/wiki/doku.php?id=sourcecode-types).
>>
>> Perhaps "tls-presentation" would be acceptable? This was used for similar
>> sourcecode in RFCs 9420 and 9458.
>>
>> If the current list of preferred values for "type" does not contain an
>> applicable type, then feel free to suggest a new one. Also, it is
>> acceptable to leave the "type" attribute not set.
>> -->
>
> tls-presentation seems like the right one.
>
> We weren't aware of its existence - thanks!
>
>> 14) <!-- [rfced] Terminology
>>
>> a) We see both "Cookie" and "cookie" used in this document. Should these be
>> uniform? If so, please let us know which form is preferred.
>
> No, the current usage is correct.
>
> Perhaps, we should wrap the capital Cookie in <tt/> (since it's a
> protocol element).
>
>> b) We see the following forms used in the document? Please review and let
>> us know if any updates are needed for correctness and consistency.
>>
>> Return Routability Check message
>> RRC message
>> return_routability_check message
>
> "RRC message" and "Return Routability Check message" are equivalent.
> If you prefer, for consistency we could always use "Return Routability
> Check message".
>
> return_routability_check is an alias when we discuss protocol elements.
>
>> c) Is "CID-address binding" correct, or should this be updated to "CID
>> address binding" (no hyphen)?
>
> The binding is between a CID and an IP/UDP address, so I guess
> "CID-address binding" is the correct way to express that.
>
>> d) We see that "return routability check" and its acronym "RRC" are used
>> throughout the document. Would you like to expand the first instance and
>> then use the acronym in the remainder of the document? Or do you prefer the
>> current arrangement?
>> -->
>
> The current arrangement is OK.
>
>> 15) <!-- [rfced] FYI - We have added expansions for the following
>> abbreviations per Section 3.6 of RFC 7322 ("RFC Style Guide"). Please
>> review each expansion in the document carefully to ensure correctness.
>>
>> Constrained Application Protocol (CoAP)
>> cryptographically secure pseudorandom number generator (CSPRNG)
>> -->
>
> Thank you!
>
>> 16) <!-- [rfced] Please review the "Inclusive Language" portion of the
>> online Style Guide
>> <https://www.rfc-editor.org/styleguide/part2/#inclusive_language>
>> and let us know if any changes are needed. Updates of this nature typically
>> result in more precise language, which is helpful for readers.
>>
>> Note that our script did not flag any words in particular, but this should
>> still be reviewed as a best practice.
>> -->
>
> On rereading it, nothing stood out.
>
> We hava couple of questions re: RFC8446bis and RFC8447bis references.
>
> We make normative references to RFC8446 and RFC8447.
>
> Their "bis" documents are:
> - draft-ietf-tls-rfc8447bis (PUB as RFC 9847)
> - draft-ietf-tls-rfc8446bis (currently in AUTH48, to become RFC 9846)
>
> These documents are in the same publication cluster (C430) as RRC, and
> respectively update and obsolete their counterparts.
>
> Two questions:
> 1. Should the references in RRC be updated (at least, RFC8447 to RFC9847)?
> 2. Should RRC wait for RFC-to-be 9846 to be published?
>
> cheers, thanks!
>
> Achim, Hannes, Thomas
>
>> Thank you.
>>
>> Rebecca VanRheenen and Sandy Ginoza
>> RFC Production Center
>
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