Re: [secdir] Benjamin Kaduk's Discuss on draft-ietf-payload-tsvcis-03: (with DISCUSS and COMMENT)

Barry Leiba <barryleiba@computer.org> Mon, 24 February 2020 05:34 UTC

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From: Barry Leiba <barryleiba@computer.org>
Date: Sun, 23 Feb 2020 21:33:45 -0800
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To: Benjamin Kaduk <kaduk@mit.edu>
Cc: Ali Begen <ali.begen@networked.media>, Catherine Meadows <catherine.meadows@nrl.navy.mil>, "Dave Satterlee (Vocal)" <Dave.Satterlee@vocal.com>, IETF SecDir <secdir@ietf.org>, IETF discussion list <ietf@ietf.org>, "Roni Even (A)" <roni.even@huawei.com>, The IESG <iesg@ietf.org>, avt@ietf.org, avtcore-chairs@ietf.org, draft-ietf-payload-tsvcis@ietf.org, draft-ietf-payload-tsvcis.all@ietf.org, victor.demjanenko@vocal.com
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Subject: Re: [secdir] Benjamin Kaduk's Discuss on draft-ietf-payload-tsvcis-03: (with DISCUSS and COMMENT)
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Hi, Victor... your turn now...

Barry

On Fri, Feb 14, 2020 at 11:43 AM Benjamin Kaduk <kaduk@mit.edu> wrote:

> Hi Barry,
>
> As Victor notes, this one was/is waiting on me; he did reply (offlist) on
> 15 January but I seem to have missed it amid a deluge of other mail that
> arrived at that time.  Thanks for the reminder, and thanks Victor for
> re-sending the comments.
> (inline)
>
> On Fri, Feb 14, 2020 at 08:20:54AM -0500, victor.demjanenko@vocal.com
> wrote:
> > HI Barry,
> >
> > Thanks for recalling this was still outstanding.  I had emailed Ben just
> after the holidays and did not realize we had no response.  The below is
> what we suggested to Ben to address concerns he raised.
> >
> > --------------------
> > Hi Ben,
> >
> > Hope your holidays were good.  Our were both good and busy.  Deliveries
> for two NASA projects and the holidays kept us from responding sooner.  But
> we do want to get this draft completed.
> >
> > With your permission, I’d like to address your comments directly,
> resolve what changes we should make and then publish a new version with a
> summary of our out-of-band discussions.  We don’t have a lot of experience
> with drafting such documents and would like to know exactly what is needed
> to make this draft acceptable.
> >
> > I believe there are two comments/issues to address:
> >
> > 1)    CODA, CODB
> >
> > Your comment ends by stating:  “(Or, of course, the use of CODB as an
> alternating 1/0 bit as the framing usage could be documented instead.)”  We
> can do this as follows:
> >
> > (original)
> > It should be noted that CODB for MELPe 600 bps mode MAY deviate from
> >    the value in Table 1 when bit 55 is used as an end-to-end framing
> >    bit. Frame decoding would remain distinct as CODA being zero on its
> >    own would indicate a 7-byte frame for either 2400 or 600 bps rate and
> >    the use of 600 bps speech coding could be deduced from the RTP
> >    timestamp (and anticipated by the SDP negotiations).
> >
> > (adding “alternating 1/0”)
> > It should be noted that CODB for MELPe 600 bps mode MAY deviate from
> >    the value in Table 1 when bit 55 is used as an alternating 1/0
> end-to-end framing
> >    bit. Frame decoding would remain distinct as CODA being zero on its
> >    own would indicate a 7-byte frame for either 2400 or 600 bps rate and
> >    the use of 600 bps speech coding could be deduced from the RTP
> >    timestamp (and anticipated by the SDP negotiations).
> >
> > I think this change would be sufficient to address your concern about
> what to expect for CODB.
>
> This looks like the minimal sufficient change, yes.  (I use "minimal"
> because I would say more if I was writing it, but I don't think I can
> insist that you write it the way I would -- it's your document after all!)
>
> > 2.    Packing and unpacking
> >
> > You are correct that I am trying to vaguely describe a middle layer shim
> that is neither RTP nor speech coder.  So it definitely does need to be
> clear.  The vagueness comes from the speech coder description being a FOUO
> document.  Its now unclassified so I can potentially say more (and I did
> make some enhancements of the parameter description already).
> >
> > So I am trying to understand exactly what you think is vague in our
> current description:
> >
> > TSVCIS augmented speech data is derived from the signal processing
> >    and data already performed by the MELPe speech coder.  For the
> >    purposes of this specification, only the general parameter nature of
> >    TSVCIS will be characterized.  Depending on the bandwidth available
> >    (and FEC requirements), a varying number of TSVCIS-specific speech
> >    coder parameters need to be transported.  These are first byte-packed
> >    and then conveyed from encoder to decoder.
> >
> >    Byte packing of TSVCIS speech data into packed parameters is
> >    processed as per the following example:
> >
> >       Three-bit field: bits A, B, and C (A is MSB, C is LSB)
> >       Five-bit field: bits D, E, F, G, and H (D is MSB, H is LSB)
> >
> >            MSB                                              LSB
> >             0      1      2      3      4      5      6      7
> >         +------+------+------+------+------+------+------+------+
> >         |   H  |   G  |   F  |   E  |   D  |   C  |   B  |   A  |
> >         +------+------+------+------+------+------+------+------+
> >
> >    This packing method places the three-bit field "first" in the lowest
> >    bits followed by the next five-bit field.  Parameters may be split
> >    between octets with the most significant bits in the earlier octet.
> >    Any unfilled bits in the last octet MUST be filled with zero.
>
> [not actually relevant to the Discuss part, but if there is always exactly
> one 3-bit parameter and one 5-bit parameter, then this text allowing
> splitting across octets will never be used and is potentially confusing to
> mention.]
>
> >    In order to accommodate a varying amount of TSVCIS augmented speech
> >    data, it is only necessary to specify the number of octets containing
> >    the packed TSVCIS parameters.  The encoding to do so is presented in
>
> I think the "only necessary to specify the number of octets" is the key
> stumbling point, for me -- I need to know the number of octets as well as
> the order of the parameters within the list, which is more information than
> just the number of octets.
>
> >    Section 3.2.  TSVCIS specifically uses the NRL VDR in two
> >    configurations using 15 and 35 packed octet parameters [TSVCIS].
>
> I think I failed to internalize the "two configurations using 15 and 35
> packed octet parameters" the first time I read the document, as this does
> help give the reader a clue that [TSVCIS] gives a good picture of what
> parameters go where.  So it seems like we could easily append to that, for
> "using a fixed set of 15 and 35 packed octet parameters in a fixed order
> [TSVCIS]" and that would resolve my concerns.
>
> > The speech coder description of the parameters is the following:
> >
> >
> >
> > So the three bit pitch is first (bits 56 to 58), followed by a five bit
> amplitude (bits 59 to 63) and then an array of spectral components, each
> 8-bit wide (starting at bit 64).
>
> [And maybe TSVCIS specifes that the spectral components are derived from
> some fundamental harmonic decomposition that naturally quantizes to a
> number-of-parameters/accuracy tradeoff with a natural order.  If so, we
> could also rely on that instead of my proposed change above; let me know if
> you want to explore that path further.]
>
> > Based on this information, I’m not sure what we should add to our draft
> to make the description of packing/unpacking clearer.  Can you make any
> suggestions or does this table help you with what you did not know?  (I
> don’t think I should put this table into the draft RFC however.)
>
> Hopefully the above helps to clarify.
>
> Thanks, and sorry for the delay.
>
> -Ben
>
> > Thanks for your attention and comments.
> >
> > Victor & Dave
> >
> >
> >
> > -----Original Message-----
> > From: Barry Leiba <barryleiba@computer.org>
> > Sent: Friday, February 14, 2020 7:38 AM
> > To: Benjamin Kaduk <kaduk@mit.edu>
> > Cc: victor.demjanenko@vocal.com; Roni Even (A) <roni.even@huawei.com>om>;
> The IESG <iesg@ietf.org>rg>; Catherine Meadows <
> catherine.meadows@nrl.navy.mil>gt;; IETF SecDir <secdir@ietf.org>rg>;
> draft-ietf-payload-tsvcis@ietf.org; Ali Begen <ali.begen@networked.media>ia>;
> avtcore-chairs@ietf.org; avt@ietf.org; Dave Satterlee (Vocal) <
> Dave.Satterlee@vocal.com>gt;; IETF discussion list <ietf@ietf.org>rg>;
> draft-ietf-payload-tsvcis.all@ietf.org
> > Subject: Re: Benjamin Kaduk's Discuss on draft-ietf-payload-tsvcis-03:
> (with DISCUSS and COMMENT)
> >
> > This is still outstanding, since November.  Victor, where are we on this
> one?
> >
> > Barry
> >
> > On Mon, Nov 25, 2019 at 1:46 AM Benjamin Kaduk <kaduk@mit.edu> wrote:
> > >
> > > Hi Victor,
> > >
> > > On Tue, Nov 19, 2019 at 03:14:21PM -0500, victor.demjanenko@vocal.com
> wrote:
> > > > Hi Ben,
> > > >
> > > > Sorry I overlooked sending you a response.  I would like to address
> > > > the two concerns you have by explaining what the speech coders are
> doing.
> > >
> > > Thanks for the extra clarifications.  To supply one of my own: I'm not
> > > concerned that the protocol doesn't work as implemented, but just want
> > > to make sure that the document includes enough information to admit
> > > new implementations without guesswork.  That is to say, "either tell
> > > me how to do it or tell me where to look that tells me how to do it".
> > >
> > > > WRT to 600 bps MELP, there is one TSVCIS mode that uses one bit
> > > > beyond the 54-bit frame for MELP 600 as a frame sync which
> alternates between frames.
> > > > With two or more MELP 600bps frames in one RTP packet, if any frame
> > > > indicates 600 bps by CODA being 0 and CODB being 1, then we know the
> > > > stream is 600bps.  If there is a single frame in an RTP packet, you
> > > > can still deduce this by looking at every other RTP packet (every
> > > > other MELP 600bps
> > > > frame) and by the timestamp advance.  Most likely the two ends would
> > > > negotiate 600 bps in SDP anyways so there really should not be a
> > > > problem.  I know it's not pretty but its workable.  I hope this
> > > > explanation helps you with the concerns for this issue.
> > >
> > > In this case, the use as an "end-to-end framing bit" (i.e., the
> > > alternating behavior you describe above) is not explicitly stated; one
> > > might imagine a scheme where the framing usage is to have the bit
> > > cycle through 1, 1, 0, and 0, or some other scheme.  I'd suggest to
> > > note in the document that if any instance of (CODA, CODB) == (0, 1) is
> > > observed, then the 600bps mode is in use.  It might also be helpful to
> > > include the observation that two successive MELPe payloads with CODA
> > > == CODB == 0 indicates the 2400bps mode (and that seeing them in a
> > > single RTP packet is decisive, whereas additional information about
> > > packet non-loss would be needed in the one-MELPe-frame-per-RTP-packet
> > > case), but that would be a fair bit of additional text and might be
> > > diminishing returns.  (Or, of course, the use of CODB as an
> > > alternating 1/0 bit as the framing usage could be documented
> > > instead.)
> > >
> > > > As for the TSVCIS parameter packing/unpacking, this is really
> > > > simple.  There is exactly on three bit parameter, exactly one five
> > > > bit parameter and a variable number of eight bit parameters.  In our
> > > > view, the speech coder itself (or a wrapper for it) is responsible
> > > > for preparing the block of octets.  RTP then just transports it.  On
> > > > receive, the complementary wrapper reverses the packing operation.
> > > > I hope this clarifies and explains the simplicity.
> > >
> > > That's exactly what I expected to happen; however, it's not what I
> > > believe the current text of the document is describing.  Specifically,
> > > I think that the current text implies that the "preparing the block of
> > > octets" and "complementary wrapper reverses the packing operation" are
> > > supposed to be part of the RTP payload format that this document
> > > describes, but this document does not have enough information to
> > > actually perform those operations reversibly.  If the packing is to be
> > > done in the speech coder, then this document doesn't need to talk
> > > about the packing at all (e.g., at the end of Section 2); if we need
> > > to keep the packing/wrapper in this document then we need to indicate
> > > that there's a defined priority order for the (8-octet) TSVCIS
> > > parameters in the TSVCIS references, to allow the packing/unpacking to
> be deterministic.
> > >
> > > Thanks,
> > >
> > > Ben
> > >
> > > >
> > > > -----Original Message-----
> > > > From: Benjamin Kaduk <kaduk@mit.edu>
> > > > Sent: Thursday, October 31, 2019 8:12 PM
> > > > To: Barry Leiba <barryleiba@computer.org>
> > > > Cc: victor.demjanenko@vocal.com; Roni Even (A)
> > > > <roni.even@huawei.com>om>; The IESG <iesg@ietf.org>rg>; Catherine Meadows
> > > > <catherine.meadows@nrl.navy.mil>il>; IETF SecDir <secdir@ietf.org>rg>;
> > > > draft-ietf-payload-tsvcis@ietf.org; Ali Begen
> > > > <ali.begen@networked.media>ia>; avtcore-chairs@ietf.org; avt@ietf.org;
> > > > Dave Satterlee (Vocal) <Dave.Satterlee@vocal.com>om>; IETF discussion
> > > > list <ietf@ietf.org>rg>; draft-ietf-payload-tsvcis.all@ietf.org
> > > > Subject: Re: Benjamin Kaduk's Discuss on
> > > > draft-ietf-payload-tsvcis-03: (with DISCUSS and COMMENT)
> > > >
> > > > I don't think so, unfortunately.
> > > >
> > > > I do see the clarification about CODB's potential for deviation from
> > > > Table 1, that only the 600 bps MELPe is allowed to deviate, and that
> > > > CODA gets us to "it's one of 2400 or 600 bps" and the RTP timestamp
> > > > disambiguates that
> > > > 600 bps is in use.  But, it seems that this means that the recipient
> > > > in general should not rely on CODB to differentiate 600 from 2400
> > > > bps, and instead is more robustly implemented by *always* using the
> > > > RTP timestamp to detect 600 bps, since that will always work and
> > > > CODB will sometimes not work under conditions not fully specified
> > > > here.  So, if we are unwilling or unable to clarify what those
> > > > conditions are (e.g., whether at a minimum mutual agreement is
> > > > required), then I think we need to describe this procedure of
> > > > consulting the RTP timestamp as the default behavior and avoid
> giving the impression that CODB should be used to do so.
> > > >
> > > > Additionally, I don't see anything to address my concern about
> > > > TSVCIS parameter decoding.  To be clear, the procedure I see this
> > > > document describing is that:
> > > > - TSVCIS gives parameters (and their lengths in bits) to the codec
> > > >   described in this document
> > > > - this document specifies how to densely encode those parameters
> into a
> > > >   byetstream
> > > > - RTP transmits that encoded bytestream to the peer
> > > > - the codec specified by this is responsible for turning that encoded
> > > >   bystream back into a list of TSVCIS parameters (and their length
> > > > in bits)
> > > >
> > > > I don't see how that last step is attainable with only the
> > > > information provided by this document.  I *assume* that one of the
> > > > TSVCIS specifications has a canonical (ordered) listing of
> > > > parameters, and that the list of parmeters given to this codec in
> > > > the first step will always be an initial prefix of that list, but
> > > > that's just me guessing at how to make sense of the stated procedure
> > > > given insufficient information.  I don't think it's appropriate to
> > > > make the reader of an RFC guess at what to do; we need to either say
> > > > how to do it or give a pointer to an external reference that does.
> > > >
> > > > -Ben
> > > >
> > > > On Tue, Oct 29, 2019 at 02:26:09PM -0400, Barry Leiba wrote:
> > > > > Ben, does the -04 version address everything?
> > > > >
> > > > > Barry
> > > > >
> > > > > On Thu, Oct 24, 2019 at 1:42 PM <victor.demjanenko@vocal.com>
> wrote:
> > > > > >
> > > > > > I forgot to address security comments in one email.  The changes
> are:
> > > > > >
> > > > > > Section 8, second paragraph - Suggested edit by reviewer
> > > > > >
> > > > > > (was)
> > > > > >    This RTP payload format and the TSVCIS decoder do not exhibit
> any
> > > > > >    significant non-uniformity in the receiver-side computational
> > > > > >    complexity for packet processing and thus are unlikely to
> pose a
> > > > > >    denial-of-service threat due to the receipt of pathological
> data.
> > > > > >    Additionally, the RTP payload format does not contain any
> active
> > > > > >    content.
> > > > > >
> > > > > > (now)
> > > > > >    This RTP payload format and the TSVCIS decoder, to the best
> of our
> > > > > >    knowledge, do not exhibit any significant non-uniformity in
> the
> > > > > >    receiver-side computational complexity for packet processing
> and thus
> > > > > >    are unlikely to pose a denial-of-service threat due to the
> receipt of
> > > > > >    pathological data. Additionally, the RTP payload format does
> not
> > > > > >    contain any active content.
> > > > > >
> > > > > >
> > > > > > Section 8, third paragraph - Suggested edit by reviewer
> > > > > >
> > > > > > (was)
> > > > > >    Please see the security considerations discussed in [RFC6562]
> > > > > >    regarding VAD and its effect on bitrates.
> > > > > >
> > > > > > (now)
> > > > > >    Please see the security considerations discussed in [RFC6562]
> > > > > >    regarding Voice Activity Detect (VAD) and its effect on
> bitrates.
> > > > > >
> > > > > > Victor
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: victor.demjanenko@vocal.com <victor.demjanenko@vocal.com>
> > > > > > Sent: Thursday, October 24, 2019 10:05 AM
> > > > > > To: 'Roni Even (A)' <roni.even@huawei.com>om>; 'Benjamin Kaduk'
> > > > > > <kaduk@mit.edu>du>; 'The IESG' <iesg@ietf.org>
> > > > > > Cc: draft-ietf-payload-tsvcis@ietf.org; 'Ali Begen'
> > > > > > <ali.begen@networked.media>ia>; avtcore-chairs@ietf.org;
> > > > > > avt@ietf.org; 'Dave Satterlee (Vocal)'
> > > > > > <Dave.Satterlee@vocal.com>
> > > > > > Subject: RE: Benjamin Kaduk's Discuss on
> > > > > > draft-ietf-payload-tsvcis-03: (with DISCUSS and COMMENT)
> > > > > >
> > > > > > Hi Everyone,
> > > > > >
> > > > > > First we want to thank everyone for their review and comments
> > > > > > for this
> > > > draft RFC.  We believe we reviewed all the comments and suggestions
> > > > and incorporated them adequately in the next draft (04).  We'd like
> > > > to send out this list of exact changes in case anyone has additional
> > > > comments or thinks the clarifications are inadequate.  We would be
> > > > most happy to address concerns before publishing draft 04 tomorrow.
> > > > > >
> > > > > > With so many emails from a half dozen or more reviewers, we
> > > > > > apologize
> > > > that we cannot address each sender individually.  We hope this
> > > > detail is sufficient for everyone.
> > > > > >
> > > > > > Again, many thanks to all.
> > > > > >
> > > > > > Victor & Dave
> > > > > >
> > > > > > ----------------------------------------------------------------
> > > > > > ----
> > > > > > --------------------------
> > > > > >
> > > > > > Section 1.1 - Suggested reference to RFC 8088 added.
> > > > > >
> > > > > > (was)
> > > > > >    Best current practices for writing an RTP payload format
> > > > > >    specification were followed [RFC2736].
> > > > > >
> > > > > > (now)
> > > > > >    Best current practices for writing an RTP payload format
> > > > > >    specification were followed [RFC2736] [RFC8088].
> > > > > >
> > > > > >
> > > > > > Section 2, paragraphs 3 and 4 - Suggested edits by reviewers
> > > > > >
> > > > > > (was)
> > > > > >    In addition to the augmented speech data, the TSVCIS
> specification
> > > > > >    identifies which speech coder and framing bits are to be
> encrypted,
> > > > > >    and how they are protected by forward error correction (FEC)
> > > > > >    techniques (using block codes).  At the RTP transport layer,
> only the
> > > > > >    speech coder related bits need to be considered and are
> conveyed in
> > > > > >    unencrypted form.  In most IP-based network deployments,
> standard
> > > > > >    link encryption methods (SRTP, VPNs, FIPS 140 link encryptors
> or Type
> > > > > >    1 Ethernet encryptors) would be used to secure the RTP speech
> > > > > >    contents.  Further, it is desirable to support the highest
> voice
> > > > > >    quality between endpoints which is only possible without the
> overhead
> > > > > >    of FEC.
> > > > > >
> > > > > >    TSVCIS augmented speech data is derived from the signal
> processing
> > > > > >    and data already performed by the MELPe speech coder.  For the
> > > > > >    purposes of this specification, only the general parameter
> nature of
> > > > > >    TSVCIS will be characterized.  Depending on the bandwidth
> available
> > > > > >    (and FEC requirements), a varying number of TSVCIS specific
> speech
> > > > > >    coder parameters need to be transported.  These are first
> byte-packed
> > > > > >    and then conveyed from encoder to decoder.
> > > > > >
> > > > > > (now)
> > > > > >    In addition to the augmented speech data, the TSVCIS
> specification
> > > > > >    identifies which speech coder and framing bits are to be
> encrypted,
> > > > > >    and how they are protected by forward error correction (FEC)
> > > > > >    techniques (using block codes).  At the RTP transport layer,
> only the
> > > > > >    speech-coder-related bits need to be considered and are
> conveyed in
> > > > > >    unencrypted form.  In most IP-based network deployments,
> standard
> > > > > >    link encryption methods (SRTP, VPNs, FIPS 140 link encryptors
> or Type
> > > > > >    1 Ethernet encryptors) would be used to secure the RTP speech
> > > > > >    contents.
> > > > > >
> > > > > >    TSVCIS augmented speech data is derived from the signal
> processing
> > > > > >    and data already performed by the MELPe speech coder.  For the
> > > > > >    purposes of this specification, only the general parameter
> nature of
> > > > > >    TSVCIS will be characterized.  Depending on the bandwidth
> available
> > > > > >    (and FEC requirements), a varying number of TSVCIS-specific
> speech
> > > > > >    coder parameters need to be transported.  These are first
> byte-packed
> > > > > >    and then conveyed from encoder to decoder.
> > > > > >
> > > > > >
> > > > > > Section 3, last sentence paragraph 3 - Suggested edit by
> > > > > > reviewer
> > > > > >
> > > > > > (was)
> > > > > >    When more than one codec data frame is
> > > > > >    present in a single RTP packet, the timestamp is, as always,
> that of
> > > > > >    the oldest data frame represented in the RTP packet.
> > > > > >
> > > > > > (now)
> > > > > >    When more than one codec data frame is
> > > > > >    present in a single RTP packet, the timestamp specified is
> that of
> > > > > >    the oldest data frame represented in the RTP packet.
> > > > > >
> > > > > >
> > > > > > Section 3.1, last paragraph - Clarified permission for MELP 600
> > > > > > end-to-end framing bit
> > > > > >
> > > > > > (was)
> > > > > >    It should be noted that CODB for both the 2400 and 600 bps
> modes MAY
> > > > > >    deviate from the values in Table 1 when bit 55 is used as an
> end-to-
> > > > > >    end framing bit.  Frame decoding would remain distinct as
> CODA being
> > > > > >    zero on its own would indicate a 7-byte frame for either rate
> and the
> > > > > >    use of 600 bps speech coding could be deduced from the RTP
> timestamp
> > > > > >    (and anticipated by the SDP negotiations).
> > > > > >
> > > > > > (now)
> > > > > >    It should be noted that CODB for MELPe 600 bps mode MAY
> deviate from
> > > > > >    the value in Table 1 when bit 55 is used as an end-to-end
> framing
> > > > > >    bit. Frame decoding would remain distinct as CODA being zero
> on its
> > > > > >    own would indicate a 7-byte frame for either 2400 or 600 bps
> rate and
> > > > > >    the use of 600 bps speech coding could be deduced from the RTP
> > > > > >    timestamp (and anticipated by the SDP negotiations).
> > > > > >
> > > > > >
> > > > > > Section 3.2, first paragraph - Clarifications requested by
> > > > > > reviewers
> > > > > >
> > > > > > (was)
> > > > > >    The TSVCIS augmented speech data as packed parameters MUST be
> placed
> > > > > >    immediately after a corresponding MELPe 2400 bps payload in
> the same
> > > > > >    RTP packet.  The packed parameters are counted in octets
> (TC).  In
> > > > > >    the preferred placement, shown in Figure 6, a single trailing
> octet
> > > > > >    SHALL be appended to include a two-bit rate code, CODA and
> CODB,
> > > > > >    (both bits set to one) and a six-bit modified count (MTC).
> The
> > > > > >    special modified count value of all ones (representing a MTC
> value of
> > > > > >    63) SHALL NOT be used for this format as it is used as the
> indicator
> > > > > >    for the alternate packing format shown next.  In a standard
> > > > > >    implementation, the TSVCIS speech coder uses a minimum of 15
> octets
> > > > > >    for parameters in octet packed form.  The modified count
> (MTC) MUST
> > > > > >    be reduced by 15 from the full octet count (TC).  Computed
> MTC = TC-
> > > > > >    15.  This accommodates a maximum of 77 parameter octets
> (maximum
> > > > > >    value of MTC is 62, 77 is the sum of 62+15).
> > > > > >
> > > > > > (now)
> > > > > >    The TSVCIS augmented speech data as packed parameters MUST be
> placed
> > > > > >    immediately after a corresponding MELPe 2400 bps payload in
> the same
> > > > > >    RTP packet.  The packed parameters are counted in octets
> (TC).  The
> > > > > >    preferred placement SHOULD be used for TSVCIS payloads with
> TC less
> > > > > >    than or equal to 77 octets, is shown in Figure 6.  In the
> preferred
> > > > > >    placement, a single trailing octet SHALL be appended to
> include a
> > > > > >    two-bit rate code, CODA and CODB, (both bits set to one) and
> a six-
> > > > > >    bit modified count (MTC).  The special modified count value
> of all
> > > > > >    ones (representing a MTC value of 63) SHALL NOT be used for
> this
> > > > > >    format as it is used as the indicator for the alternate
> packing
> > > > > >    format shown next.  In a standard implementation, the TSVCIS
> speech
> > > > > >    coder uses a minimum of 15 octets for parameters in octet
> packed
> > > > > >    form.  The modified count (MTC) MUST be reduced by 15 from
> the full
> > > > > >    octet count (TC).  Computed MTC = TC-15.  This accommodates a
> maximum
> > > > > >    of 77 parameter octets (maximum value of MTC is 62, 77 is the
> sum of
> > > > > >    62+15).
> > > > > >
> > > > > >
> > > > > > Section 3.3, first paragraph - Suggested edit by reviewer
> > > > > >
> > > > > > (was)
> > > > > >    A TSVCIS RTP packet consists of zero or more TSVCIS coder
> frames
> > > > > >    (each consisting of MELPe and TSVCIS coder data) followed by
> zero or
> > > > > >    one MELPe comfort noise frame.  The presence of a comfort
> noise frame
> > > > > >    can be determined by its rate code bits in its last octet.
> > > > > >
> > > > > > (now)
> > > > > >    A TSVCIS RTP packet payload consists of zero or more
> consecutive
> > > > > >    TSVCIS coder frames (each consisting of MELPe 2400 and TSVCIS
> coder
> > > > > >    data), with the oldest frame first, followed by zero or one
> MELPe
> > > > > >    comfort noise frame.  The presence of a comfort noise frame
> can be
> > > > > >    determined by its rate code bits in its last octet.
> > > > > >
> > > > > >
> > > > > > Section 3.3, fourth paragraph - Clarification requested by
> > > > > > reviewers
> > > > > >
> > > > > > (was)
> > > > > >    TSVCIS coder frames in a single RTP packet MAY be of
> different coder
> > > > > >    bitrates.  With the exception for the variable length TSVCIS
> > > > > >    parameter frames, the coder rate bits in the trailing byte
> identify
> > > > > >    the contents and length as per Table 1.
> > > > > >
> > > > > > (now)
> > > > > >    TSVCIS coder frames in a single RTP packet MAY have varying
> TSVCIS
> > > > > >    parameter octet counts.  Its packed parameter octet count
> (length) is
> > > > > >    indicated in the trailing byte(s).  All MELPe frames in a
> single RTP
> > > > > >    packet MUST be of the same coder bitrate.  For all MELPe coder
> > > > > >    frames, the coder rate bits in the trailing byte identify the
> > > > > >    contents and length as per Table 1.
> > > > > >
> > > > > >
> > > > > > Section 4.1 - Editor note removed
> > > > > >
> > > > > >
> > > > > > Section 4.1 - Change controller is now
> > > > > >
> > > > > > (now)
> > > > > >    Change controller: IETF, contact <avt@ietf.org>
> > > > > >
> > > > > >
> > > > > > Section 5, first paragraph - Suggested edits by reviewers
> > > > > >
> > > > > > (was)
> > > > > >    A primary application of TSVCIS is for radio communications
> of voice
> > > > > >    conversations, and discontinuous transmissions are normal.
> When
> > > > > >    TSVCIS is used in an IP network, TSVCIS RTP packet
> transmissions may
> > > > > >    cease and resume frequently.  RTP synchronization source
> (SSRC)
> > > > > >    sequence number gaps indicate lost packets to be filled by
> PLC, while
> > > > > >    abrupt loss of RTP packets indicates intended discontinuous
> > > > > >    transmissions.
> > > > > >
> > > > > > (now)
> > > > > >    A primary application of TSVCIS is for radio communications
> of voice
> > > > > >    conversations, and discontinuous transmissions are normal.
> When
> > > > > >    TSVCIS is used in an IP network, TSVCIS RTP packet
> transmissions may
> > > > > >    cease and resume frequently.  RTP synchronization source
> (SSRC)
> > > > > >    sequence number gaps indicate lost packets to be filled by
> Packet
> > > > > >    Loss Concealment (PLC), while abrupt loss of RTP packets
> indicates
> > > > > >    intended discontinuous transmissions.  Resumption of voice
> > > > > >    transmission SHOULD be indicated by the RTP marker bit (M)
> set to 1.
> > > > > >
> > > > > >
> > > > > > Section 10 - Added reference
> > > > > >
> > > > > > (added)
> > > > > >    [RFC8088]  Westerlund, M., "How to Write an RTP Payload
> Format",
> > > > > >               RFC 8088, DOI 10.17487/RFC8088, May 2017,
> > > > > >               <http://www.rfc-editor.org/info/rfc8088>.
> > > > > >
> > > > > > ----------------------------------------------------------------
> > > > > > ----
> > > > > > -----------------------------
> > > > > >
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: Roni Even (A) <roni.even@huawei.com>
> > > > > > Sent: Sunday, October 6, 2019 2:09 AM
> > > > > > To: victor.demjanenko@vocal.com; 'Benjamin Kaduk'
> > > > > > <kaduk@mit.edu>du>; 'The IESG' <iesg@ietf.org>
> > > > > > Cc: draft-ietf-payload-tsvcis@ietf.org; 'Ali Begen'
> > > > > > <ali.begen@networked.media>ia>; avtcore-chairs@ietf.org;
> > > > > > avt@ietf.org; 'Dave Satterlee (Vocal)'
> > > > > > <Dave.Satterlee@vocal.com>
> > > > > > Subject: RE: Benjamin Kaduk's Discuss on
> > > > > > draft-ietf-payload-tsvcis-03: (with DISCUSS and COMMENT)
> > > > > >
> > > > > > Hi,
> > > > > > About the reference to TSVCIS.
> > > > > > The RTP payload is about how to encapsulate the payload in an
> > > > > > RTP
> > > > packet. The objective is to define how an RTP stack can insert the
> > > > tsvcis frames and  extract the tsvcis frames from the RTP packet.
> > > > Typically it is not required to understand the payload structure in
> > > > order to be able to perform the encapsulation.
> > > > > > This is why the reference to the payload is Informational and we
> > > > > > did not require to have it publically available.  If there is a
> > > > > > need to understand the payload itself for the encapsulating than
> > > > > > we need more information in the RTP payload specification and a
> > > > > > publically available normative reference. I think this is not
> > > > > > the case here
> > > > > >
> > > > > > Roni Even
> > > > > >
> > > > > > AVTCore co-chair (ex Payload)
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: victor.demjanenko@vocal.com
> > > > > > [mailto:victor.demjanenko@vocal.com]
> > > > > > Sent: Saturday, October 05, 2019 12:18 AM
> > > > > > To: 'Benjamin Kaduk'; 'The IESG'
> > > > > > Cc: draft-ietf-payload-tsvcis@ietf.org; 'Ali Begen';
> > > > avtcore-chairs@ietf.org; avt@ietf.org; 'Victor Demjanenko, Ph.D.';
> > > > 'Dave Satterlee (Vocal)'
> > > > > > Subject: RE: Benjamin Kaduk's Discuss on
> > > > > > draft-ietf-payload-tsvcis-03: (with DISCUSS and COMMENT)
> > > > > >
> > > > > > Everyone,
> > > > > >
> > > > > > Thanks for the comments.  I think I mis-understood the ambiguity
> > > > > > with
> > > > respect to to changing rates within a RTP packet.  That was not
> > > > plan.  An RTP packet must have MELP speech frames of the same rate.
> > > > What is possible is that the amount of augmented TSVCIS speech data
> > > > may vary from one speech frame to the next.  This allows for a
> > > > dynamic VDR as suggested by the NRL paper.  So an RTP packet may
> > > > have varying TSVCIS data but must always have MELPe 2400 data.
> > > > > >
> > > > > > Again backwards parsing is necessary but the timestamp uniformly
> > > > increments 22.5msec per combined MELP/TSVCIS speech frame.
> > > > > >
> > > > > > The NRL is a good public reference on the VDR aspects.  The
> > > > > > actual
> > > > TSVCIS spec we had was FOUO so we could not replicate its detail.
> > > > (I believe a later spec is public or at least partially public.  I
> > > > am trying to get this.)  The opaque data is pretty obvious with the
> TSVCIS spec in hand.
> > > > > >
> > > > > > We will address the issues/concerns raised next week.  Other
> > > > > > business
> > > > had priority.
> > > > > >
> > > > > > Thank you and enjoy the weekend.
> > > > > >
> > > > > > Regards,
> > > > > >
> > > > > > Victor & Dave
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: Benjamin Kaduk via Datatracker <noreply@ietf.org>
> > > > > > Sent: Wednesday, October 2, 2019 10:40 PM
> > > > > > To: The IESG <iesg@ietf.org>
> > > > > > Cc: draft-ietf-payload-tsvcis@ietf.org; Ali Begen
> > > > > > <ali.begen@networked.media>ia>; avtcore-chairs@ietf.org;
> > > > > > ali.begen@networked.media; avt@ietf.org
> > > > > > Subject: Benjamin Kaduk's Discuss on
> draft-ietf-payload-tsvcis-03:
> > > > > > (with DISCUSS and COMMENT)
> > > > > >
> > > > > > Benjamin Kaduk has entered the following ballot position for
> > > > > > draft-ietf-payload-tsvcis-03: Discuss
> > > > > >
> > > > > > When responding, please keep the subject line intact and reply
> > > > > > to all email addresses included in the To and CC lines. (Feel
> > > > > > free to cut this introductory paragraph, however.)
> > > > > >
> > > > > >
> > > > > > Please refer to
> > > > > > https://www.ietf.org/iesg/statement/discuss-criteria.html
> > > > > > for more information about IESG DISCUSS and COMMENT positions.
> > > > > >
> > > > > >
> > > > > > The document, along with other ballot positions, can be found
> here:
> > > > > > https://datatracker.ietf.org/doc/draft-ietf-payload-tsvcis/
> > > > > >
> > > > > >
> > > > > >
> > > > > > ----------------------------------------------------------------
> > > > > > ----
> > > > > > --
> > > > > > DISCUSS:
> > > > > > ----------------------------------------------------------------
> > > > > > ----
> > > > > > --
> > > > > >
> > > > > > I support Magnus' point about the time-ordering of adjacent
> > > > > > frames in a
> > > > packet.
> > > > > >
> > > > > > Additionally, I am not sure that there's quite enough here to be
> > > > interoperably implementable.  Specifically, we seem to be lacking a
> > > > description of how an encoder or decoder knows which TSVCIS
> > > > parameters, and in what order, to byte-pack or unpack,
> respectively.
> > > > One might surmise that there is a canonical listing in [TSVCIS], but
> > > > this document does not say that, and furthermore [TSVCIS] is only
> listed as an informative reference.
> > > > (I couldn't get my hands on my copy, at least on short notice.)  If
> > > > we limited ourselves to treating the TSVCIS parameters as an
> > > > entirely opaque blob (codec, convey these N octets to the peer with
> > > > the appropriate one- or two-byte trailer for payload type
> > > > identification and framing), that would be interoperably
> > > > implementable, since the black-box bits are up to some other codec
> to interpret.
> > > > > >
> > > > > > In a similar vein, we mention but do not completely specify the
> > > > potential for using CODB as an end-to-end framing bit, in Section
> > > > 3.1 (see Comment), which is not interoperably implementable without
> further details.
> > > > > >
> > > > > >
> > > > > > ----------------------------------------------------------------
> > > > > > ----
> > > > > > --
> > > > > > COMMENT:
> > > > > > ----------------------------------------------------------------
> > > > > > ----
> > > > > > --
> > > > > >
> > > > > > Where is [TSVCIS] available?
> > > > > >
> > > > > > Is [NRLVDR] the same as
> > > > > > https://apps.dtic.mil/dtic/tr/fulltext/u2/a588068.pdf ?  A URL
> > > > > > in the
> > > > references would be helpful.
> > > > > >
> > > > > > Is additional TSVCIS data only present after 2400bps MELPe and
> > > > > > the first
> > > > thing to get dropped under bandwidth pressure?  The abstract and
> > > > introduction imply this by calling out MELPe 2400 bps speech
> > > > parameters explicitly, but Section 3 says that TSVCIS augments
> > > > standard 600, 1200, and
> > > > 2400 bps MELP frames.
> > > > > >
> > > > > > It's helpful that Section 3.3 gives some general guidance for
> > > > > > decoding
> > > > this payload type ("[t]he way to determine the number of
> > > > TSVCIS/MELPe frames is to identify each frame type and length"), but
> > > > I think some generic considerations would be very helpful to the
> > > > reader much earlier, along the lines of "MELPe and TSVCIS data
> > > > payloads are decoded from the end, using the CODA and CODB (and, if
> > > > necessary, CODC and others) bits to determine the type of payload.
> > > > For MELPe payloads the type also indicates the payload length,
> > > > whereas for TSVCIS data an additional length field is present, in
> > > > one of two possible formats.  A TSVCIS coder frame consists of a
> > > > MELPe data payload followed by zero or one TSVCIS data payload;
> > > > after the TSVCIS payload's presence/length is determined, then the
> > > > preceding MELPe payload can be determined and decoded.  Per Section
> > > > 3.3, multiple TSVCIS frames can be present in a single RTP packet."
> > > > This (or something like it) would also serve to clarify the role of
> the COD* bits, which is otherwise only implicitly introduced.
> > > > > >
> > > > > > Section 1.1
> > > > > >
> > > > > > RFC 2736 is BCP 36 (but it's updated by RFC 8088 which is for
> > > > > > some
> > > > reason an Informational document and not part of BCP 36?!).
> > > > > >
> > > > > > Section 2
> > > > > >
> > > > > >    In addition to the augmented speech data, the TSVCIS
> specification
> > > > > >    identifies which speech coder and framing bits are to be
> encrypted,
> > > > > >    and how they are protected by forward error correction (FEC)
> > > > > >    techniques (using block codes).  At the RTP transport layer,
> only the
> > > > > >    speech coder related bits need to be considered and are
> conveyed in
> > > > > >    unencrypted form.  In most IP-based network deployments,
> > > > > > standard
> > > > > >
> > > > > > Am I reading this correctly that this text is just summarizing
> > > > > > what's in
> > > > the TSVCIS spec in terms of what needs to be in unencrypted form, so
> > > > the "only the speech coder related bits[...]" is not new information
> > > > from this document?  I'm not sure I agree with the conclusion,
> > > > regardless -- won't the
> > > > (MELPe) speech coder bits be enough to convey the semantic content
> > > > of the audio stream, something that one might desire to keep
> confidential?
> > > > > >
> > > > > >    link encryption methods (SRTP, VPNs, FIPS 140 link encryptors
> or Type
> > > > > >    1 Ethernet encryptors) would be used to secure the RTP speech
> > > > > >    contents.  Further, it is desirable to support the highest
> voice
> > > > > >    quality between endpoints which is only possible without the
> overhead
> > > > > >    of FEC.
> > > > > >
> > > > > > I think I'm missing a step in how this conclusion was reached.
> > > > > >
> > > > > >    TSVCIS will be characterized.  Depending on the bandwidth
> available
> > > > > >    (and FEC requirements), a varying number of TSVCIS specific
> speech
> > > > > >    coder parameters need to be transported.  These are first
> byte-packed
> > > > > >    and then conveyed from encoder to decoder.
> > > > > >
> > > > > > Per the Discuss point, how do I know which parameters need to be
> > > > transported, and in what order?
> > > > > >
> > > > > >    Byte packing of TSVCIS speech data into packed parameters is
> > > > > >    processed as per the following example:
> > > > > >
> > > > > >       Three-bit field: bits A, B, and C (A is MSB, C is LSB)
> > > > > >       Five-bit field: bits D, E, F, G, and H (D is MSB, H is
> > > > > > LSB)
> > > > > >
> > > > > >            MSB                                              LSB
> > > > > >             0      1      2      3      4      5      6      7
> > > > > >         +------+------+------+------+------+------+------+------+
> > > > > >         |   H  |   G  |   F  |   E  |   D  |   C  |   B  |   A  |
> > > > > >
> > > > > > +------+------+------+------+------+------+------+------+
> > > > > >
> > > > > >    This packing method places the three-bit field "first" in the
> lowest
> > > > > >    bits followed by the next five-bit field.  Parameters may be
> split
> > > > > >    between octets with the most significant bits in the earlier
> octet.
> > > > > >    Any unfilled bits in the last octet MUST be filled with zero.
> > > > > >
> > > > > > I agree with Adam that this is very unclear.  A is the MSB of
> > > > > > the
> > > > three-bit field but the LSB of the octet overall?
> > > > > > We probably need an example of splitting a parameter across
> > > > > > octets as
> > > > well, to get the bit ordering right.
> > > > > >
> > > > > > Section 3.1
> > > > > >
> > > > > >    It should be noted that CODB for both the 2400 and 600 bps
> modes MAY
> > > > > >    deviate from the values in Table 1 when bit 55 is used as an
> end-to-
> > > > > >    end framing bit.  Frame decoding would remain distinct as
> > > > > > CODA being
> > > > > >
> > > > > > Where is the use of CODB as an end-to-end framing bit defined?
> > > > > > If we're
> > > > going to provide neither a complete description of how to do it nor
> > > > a reference to a better description, we probably shouldn't mention
> it at all.
> > > > > >
> > > > > > Section 3.2
> > > > > >
> > > > > >    RTP packet.  The packed parameters are counted in octets
> (TC).  In
> > > > > >    the preferred placement, shown in Figure 6, a single trailing
> octet
> > > > > >    SHALL be appended to include a two-bit rate code, CODA and
> > > > > > CODB,
> > > > > >
> > > > > > I'd consider saying something about this being the preferred
> > > > > > format
> > > > > > ("placement") due to its shorter length than the alternative,
> > > > > > and say
> > > > that it "SHOULD be used for TSVCIS payloads with TC less than or
> > > > equal to 77 octetes".
> > > > > >
> > > > > > Section 3.3
> > > > > >
> > > > > > When a longer packetization interval is used, is that indicated
> > > > > > by
> > > > signaling or RTP timestamps or otherwise?
> > > > > >
> > > > > >    TSVCIS coder frames in a single RTP packet MAY be of
> different coder
> > > > > >    bitrates.  With the exception for the variable length TSVCIS
> > > > > >    parameter frames, the coder rate bits in the trailing byte
> identify
> > > > > >    the contents and length as per Table 1.
> > > > > >
> > > > > > Maybe also note that the penultimate octet gives the length
> there?
> > > > > >
> > > > > >    Information describing the number of frames contained in an
> RTP
> > > > > >    packet is not transmitted as part of the RTP payload.  The
> way to
> > > > > >    determine the number of TSVCIS/MELPe frames is to identify
> each frame
> > > > > >    type and length thereby counting the total number of octets
> within
> > > > > >    the RTP packet.
> > > > > >
> > > > > > terminology nit: if a frame is the combination of MELPe and
> > > > > > TSVCIS
> > > > payload data units then there are two layres of decoding to get a
> > > > length for the frame, since we have to get the TSVCIS length and
> then the MELPe length.
> > > > > >
> > > > > > Section 4.2
> > > > > >
> > > > > >    Parameter "ptime" cannot be used for the purpose of
> > > > > > specifying the
> > > > > >
> > > > > > nit: missing article ("The parameter")
> > > > > >
> > > > > >    will be impossible to distinguish which mode is about to be
> used
> > > > > >    (e.g., when ptime=68, it would be impossible to distinguish
> if the
> > > > > >    packet is carrying one frame of 67.5 ms or three frames of
> 22.5 ms).
> > > > > >
> > > > > > So how is the operating mode determined, then?
> > > > > > (I think this is the same question I asked above)
> > > > > >
> > > > > > Section 4.4
> > > > > >
> > > > > >    For example, if offerer bitrates are "2400,600" and answer
> bitrates
> > > > > >    are "600,2400", the initial bitrate is 600.  If other
> bitrates are
> > > > > >    provided by the answerer, any common bitrate between the
> offer and
> > > > > >    answer MAY be used at any time in the future.  Activation of
> these
> > > > > >    other common bitrates is beyond the scope of this document.
> > > > > >
> > > > > > It seems important to specify whether this requires a new O/A
> > > > > > exchange
> > > > or can be done "spontaneously" by just encoding different frame
> types.
> > > > > > (It seems like the latter is possible, on first glance, and this
> > > > > > is implied by Section 3.3's discussion of mixing them in a
> > > > > > single
> > > > > > packet.)
> > > > > >
> > > > > > Section 5
> > > > > >
> > > > > > Please expand PLC at first use (not second).
> > > > > >
> > > > > > Section 6
> > > > > >
> > > > > > I don't understand the PLC usage.  Is the idea that a receiver,
> > > > > > on
> > > > seeing an SSRC gap, constructs fictitious PLC frames to "fill the
> gap"
> > > > > > and passes the resulting stream to the decoder?
> > > > > >
> > > > > > Section 8
> > > > > >
> > > > > >    and important considerations in [RFC7201].  Applications
> SHOULD use
> > > > > >    one or more appropriate strong security mechanisms.  The rest
> of this
> > > > > >    section discusses the security-impacting properties of the
> payload
> > > > > >    format itself.
> > > > > >
> > > > > > I thought we described TSVCIS itself (much earlier in the
> > > > > > document) as
> > > > requiring encryption for some data; wouldn't that translate to a
> "MUST"
> > > > > > here and not a "SHOULD"?
> > > > > >
> > > > > >
> > > > > >
> > > >
> >
>
>