Re: [AVTCORE] Genart last call review of draft-ietf-avtcore-multi-party-rtt-mix-14

Gunnar Hellström <> Thu, 06 May 2021 21:14 UTC

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To: Peter Yee <>,
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Date: Thu, 6 May 2021 23:14:06 +0200
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Subject: Re: [AVTCORE] Genart last call review of draft-ietf-avtcore-multi-party-rtt-mix-14
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Thank you for the thorough review. Please see comments inline.

I will split the answers, and start here with answers and change 
proposals for the minor issues:

Den 2021-05-06 kl. 05:41, skrev Peter Yee via Datatracker:
> Reviewer: Peter Yee
> Review result: Ready with Issues
> I am the assigned Gen-ART reviewer for this draft. The General Area
> Review Team (Gen-ART) reviews all IETF documents being processed
> by the IESG for the IETF Chair.  Please treat these comments just
> like any other last call comments.
> For more information, please see the FAQ at
> <>.
> Document: draft-ietf-avtcore-multi-party-rtt-mix-14
> Reviewer: Peter Yee
> Review Date: 2021-05-05
> IETF LC End Date: 2021-05-03
> IESG Telechat date: Not scheduled for a telechat
> Summary: This draft specifies updates to RFC 4103 to allow real-time text
> mixing for both multiparty-aware and multiparty-unaware participants. It has
> some minor issues that should be addressed before publication. [Ready with
> issues]
> Major issues: None
> Minor issues:
> Page 7, 1st block, 13th sentence: what constitutes a “reasonable effort”? It
> might be best to drop this sentence.

[GH] This reason is important for the desicion on technology selection.

I suggest a change from:

"For best deployment opportunity, it should be possible to upgrade 
existing endpoint solutions to be multi-party aware with a reasonable 


"For best deployment opportunity, it should be feasible to upgrade 
existing endpoint solutions to become multiparty-aware."

> Page 7, 2nd block, 2nd sentence, “300 ms”: would it make sense to append
> “period” or “timeout” after this value?

[GH] I suggest to change from "every 300 ms." to "with 300 ms intervals."

> Page 13, section 3.4, 2nd paragraph, 1st sentence: in regards to “only part”,
> how is this calculated?

[GH] I suggest to change from "If the "CPS" value is reached, longer 
transmission intervals SHALL be applied and only part of the text queued 
for transmission sent at end of each transmission interval, until the 
transmission rate falls under the "CPS" value again."


"If the "CPS" value is reached, longer transmission intervals SHALL be 
applied and only as much of the text queued for transmission sent at end 
of each transmission interval that can be allowed without exceeding the 
"CPS" value, until the transmission rate falls under the "CPS" value 
again. Division of text for partial transmission MUST then be made at 
T140block borders. "

> Page 15, section 3.12, 2nd paragraph, 1st sentence: The placing of all
> available redundant levels in the packet is presumably subject to a maximum
> packet size or the “CPS” limit, if there are obnoxious levels of redundancy
> specified?

[GH] Thanks, a good observation. It is already covered in section 3.10, 
but it could be more emphasized there. In 3.12 we are only dealing with 
the redundancy, which must be possible to send and is not included in 
the "CPS" value.

I suggest that the following part of 3.10 is improved from:

"Redundant text SHALL also be included.  See Section 3.12"

"Redundant text SHALL also be included, and the assessment of how much 
new text can be included within the maximum packet size MUST take into 
account that the redundancy has priority to be transmitted in its 
entirety.  See Section 3.12."

> Page 17, section 3.17.2, 4th paragraph, 2nd sentence: “SHALL prefer” seems odd.
> It doesn’t say that the marking will actually be done. It’s just preferred. If
> you’re not going to require the marking in that sentence, then perhaps change
> “SHALL” to “SHOULD”.
[GH] Agreed. Done as proposed.
> Page 19, section 3.20, 2nd paragraph, 2nd sentence: I don’t find the “something
> specific” particularly enlightening. Like what? An identifier for the method?

[GH] Proposed to be changed from:

" In that case, the
    SDP of the offer will include something specific for that method, and
    an answer acknowledging the use of that method would accept it by
    something specific included in the SDP."


"In that case, the
    SDP of the offer will include something specific for that method, 
e.g. an SDP attribute or another media format. An answer selecting the 
use of that method would accept it by
    a corresponding acknowledgement included in the SDP."

> Page 27, section 4.2.2, 4th paragraph: can you elaborate on these “Integrity
> considerations”? Otherwise, it’s difficult to comply with the SHALL in any
> meaningful way.

[GH] The sentence was inserted after discussions with emergency service 
providers, who had an example that it would be valuable to have a 
detailed personalized label of an emergency service agent shown to other 
agents while a less personal label should be used when sent to the 
calling users in emergency.

The security aspects on the label are quite similar to the security 
aspects on the <display-text> elements specified in RFC 4575. Its 
security aspects are specified in

You are right that that example contains mainly SHOULD and RECOMMENDED 
and no SHALL.

I suggest changing:

"Integrity considerations SHALL be taken when composing the label."


"Information available to the mixer for composing the label may contain 
sensitive personal information that SHOULD not be revealed in sessions 
not securely authenticated and protected. Integrity considerations 
regarding how much personal information is included in the label SHOULD 
therefore be taken when composing the label."

> Page 33, 3rd paragraph, 1st sentence: any reason for the change from “T.140” in
> the previous and following paragraphs to “t140” in this one?
[GH] No, they should be "T.140 data channels" for all cases in that 
I have changed.
> Page 33, 6th paragraph: how is disappearance determined?
[GH]The disappearance may be signaled by the SIP conference system RFC 
4353, RFC 4575 etc. as a conference notification if that system is used, 
or simply by removal of the text media in an RTP session modification. 
There may also be a malfunction detected by keep-alive transactions not 
being maintained. I suggest to not detail how it disappears.
> Page 35, section 11, 3rd paragraph, 2nd sentence before creating a new sentence
> (see nits, below): I’m having troubles tying the adjective “secure” to each of
> the nouns in the sentence. It works for “signaling” and perhaps “media”, but
> for “authentication”, one sort of assumes that authentication mechanism is
> secure and helping to provide the security. Perhaps you could reword that
> sentence?

[GH] I propose to change the sentence from:

"Counteractions should be to require
    secure signaling, media and authentication, and to provide higher
    level conference functions e.g. for blocking and expelling


"Counteractions should be to require authentication, secure session 
signaling and secure media. Higher level conference functions should 
also be used e.g., for blocking and expelling participants who caused 
security concerns."


Gunnar Hellstrom

Gunnar Hellström