Subject: [avtext] Mirja Kühlewind's No Objection on draft-ietf-avtext-splicing-notification-07: (with COMMENT)

From: "Mirja Kuehlewind" <[email-masked]>
Date: Thu, 16 Jun 2016 06:21:05 -0700

Mirja Kühlewind has entered the following ballot position for
draft-ietf-avtext-splicing-notification-07: No Objection

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COMMENT:
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I moved my discuss points into the comment now assuming that the
discussed changes will be applied in the next version. I still support
Alia's discuss, as this point must be addressed carefully, and I would
like to review the next before final publications.

- The following action does not seem to be appropriate for a
specification of an end-to-end protocol:
"And if the splicer wishes to prevent the downstream receivers from
detecting splicing, it MUST
   NOT forward the message."
I guess if a middlebox decides to drop the message, there is not much we
can do. But I definitely would prefer to not see this specified in an
RFC.

- Why is just having the RTCP message not sufficient? Why are the RTP
extensions needed as well?

- And is the RTCP message send only once or multiple time? This is not
specified.

- There is some discussion about the implementation of the slicer in
section 5 (where btw. the title "Failure Cases" seems inappropriate),
while there is one sentence saying: "If the splicer is implemented
following [RFC6828], it will have its
   own SSRC and will send its own RTCP reports, and will forward
   translated RTCP reports from the receivers."
Why are alternatives discussed here, if there is already a recommendation
given in RFC6828? And how would proper congestion handling be ensure in
the other setups not described in RFC6828?

- As a general comment, I found it quite hard to read this doc without
reading RFC6828 which is only listed as a informative reference as it is
informational only. I think it is wrong. Further, RFC6828 describes some
action that a slicers has to perform. However, all language in RFC6828 is
non normative. This is slightly confusing to me as well. I would further
recommend to briefly give an overview of the assumed scenario is this
document.

- Minor comment: The definition of the new SDP grouping semantic should
be mentioned in the abstract and RFC4566 should be referenced. And I
don't think the SDP grouping registry requires a contact.

- Quick question: Maybe I'm missing something here but why do you need a
splicer in a scenario where "the
   substitutive sender is implemented together with the main RTP sender
inside a single device" (as written in section 2)?