Re: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments
Christer Holmberg <christer.holmberg@ericsson.com> Fri, 08 November 2019 03:59 UTC
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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Gunnar Hellström <gunnar.hellstrom@omnitor.se>, Bo Burman <bo.burman@ericsson.com>, "mmusic (mmusic@ietf.org)" <mmusic@ietf.org>
Thread-Topic: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments
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Date: Fri, 08 Nov 2019 03:59:31 +0000
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Subject: Re: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments
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Hi, I will modify as suggested. Regards, Christer ________________________________ From: Gunnar Hellström <gunnar.hellstrom@omnitor.se> Sent: Thursday, November 7, 2019 10:35 PM To: Christer Holmberg <christer.holmberg@ericsson.com>; Bo Burman <bo.burman@ericsson.com>; mmusic (mmusic@ietf.org) <mmusic@ietf.org> Subject: Re: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments Den 2019-11-07 kl. 19:04, skrev Christer Holmberg: Hi, I guess we can reference RFC 1459 - how often does that happen nowadays? :) It is not easy to find specification of the label in RFC 1459. And IRC is not important. Let us change wording from: "and e.g., include IRC style text labels in the real-time text in order for the receiver to present real-time text from different sources separated. " to "and e.g., include human readable text labels in the real-time text stream indicating the source when shift of source occurs. This would be done in order to enable the receiver to present real-time text from different sources separated. " Regards Gunnar Regards, Christer ________________________________ From: Gunnar Hellström <gunnar.hellstrom@omnitor.se><mailto:gunnar.hellstrom@omnitor.se> Sent: Thursday, November 7, 2019 6:51:19 PM To: Christer Holmberg <christer.holmberg@ericsson.com><mailto:christer.holmberg@ericsson.com>; Bo Burman <bo.burman@ericsson.com><mailto:bo.burman@ericsson.com>; mmusic (mmusic@ietf.org<mailto:mmusic@ietf.org>) <mmusic@ietf.org><mailto:mmusic@ietf.org> Subject: Re: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments Hi, I am sorry, I have not yet found a reference for the common look of messages with a leading source label that I called "IRC style". Anyone knows? Regards Gunnar Den 2019-11-07 kl. 16:01, skrev Christer Holmberg: > Hi, > > I have updated the pull request based on Bo's technical comments. Please take a look. > > https://protect2.fireeye.com/v1/url?k=e0987931-bc4c728f-e09839aa-86742d02e7e2-df3d38683e05ec32&q=1&e=9c7cc8f6-262c-4fc4-a624-42d361ef532b&u=https%3A%2F%2Fgithub.com%2Fcdh4u%2Fdraft-datachannel-t140%2Fpull%2F52 > > Gunnar, which RFC should I add as reference for the IRC labels? > > Regards, > > Christer > > > > On 07/11/2019, 15.34, "Bo Burman" <bo.burman@ericsson.com><mailto:bo.burman@ericsson.com> wrote: > > Yes, I agree that should resolve the issue I had with the text. > Thanks, > /Bo > > > -----Original Message----- > > From: Gunnar Hellström <gunnar.hellstrom@omnitor.se><mailto:gunnar.hellstrom@omnitor.se> > > Sent: den 7 november 2019 14:13 > > To: Christer Holmberg <christer.holmberg@ericsson.com><mailto:christer.holmberg@ericsson.com>; Bo Burman > > <bo.burman@ericsson.com><mailto:bo.burman@ericsson.com>; mmusic (mmusic@ietf.org<mailto:mmusic@ietf.org>) > > <mmusic@ietf.org><mailto:mmusic@ietf.org> > > Subject: Re: [MMUSIC] Starting shepherd's review of draft-ietf-mmusic-t140- > > usage-data-channel-07 - Bo's technical comments > > > > Hi, > > > > Christer, I accept your proposal below. With the remaining text it should be > > apparent for all that the solution has limitations. > > > > I hope also Bo thinks that the issues are solved now. > > > > Regards > > > > Gunnar > > > > > > Den 2019-11-07 kl. 14:06, skrev Christer Holmberg: > > > Hi, > > > > > >>> In the first paragraph we say that one needs to use separate data > > >>> channels, so it sounds strange to then have a note saying that is not true. > > Also, the way you suggest the text makes it look like you are defining a > > mechanism for using a single channel. > > >> Yes, I realized the conflict and tried to avoid it by the words > > >> "limited functionality multi-party RTT presentation in one display area", > > and "This presentation style does not meet all RTT requirements". > > >> > > >> But maybe that was not obvious. So, I accept your proposal below with > > >> some modifications > > >> > > >>> Maybe something like this: > > >>> > > >>> "The usage of a single T.140 data channel, without any protocol > > extensions, would require the conference server to only forward > > >>> real-time text from one source at any given time, and e.g., include IRC > > style text labels in the real-time text in order for the receiver > > >>> to separate real-time text from different sources. The procedures of > > such mechanism is outside the scope of this document." > > >> Yes, quite good, I suggest a few modifications to: > > >> > > >> "The usage of a single T.140 data channel, without any protocol > > >> extensions, would require the conference server to only forward > > >> real-time text from one source at any given time, and e.g., include > > >> IRC style text labels in the real-time text in order for the receiver to > > present real-time text from different sources separated. The procedures of > > such mechanisms cause functional limitations and are outside the scope of > > this document." > > > I am ok to replace 'separate' with 'present', but with the modification to the > > last sentence you would still have the question what those 'functional > > limitations' are, and we would need to include additional text... > > > > > > So, I suggest that we remove the text about functional limitations. > > > > > > Regards, > > > > > > Christer > > > > > > > > > > > > > > > > > > From: Gunnar Hellström mailto:gunnar.hellstrom@omnitor.se > > > Sent: Wednesday, November 6, 2019 9:44 PM > > > To: Christer Holmberg mailto:christer.holmberg@ericsson.com; Bo Burman > > > mailto:bo.burman=40ericsson.com@dmarc.ietf.org; mmusic > > > (mailto:mmusic@ietf.org) mailto:mmusic@ietf.org > > > Subject: Re: [MMUSIC] Starting shepherd's review of > > > draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments > > > > > > Hi, > > > Even if I accepted to delete the last sentence in section 5 on multi-party, I > > want to propose a solution that might better address the original issue 5. > > > > > > So, this is a proposal for new wording of the last sentence in 5, as a solution > > on issue 5: > > > "Conference mixers that use a single T.140 data channel > > > to transmit real-time text towards clients might however without any > > protocol extensions produce a limited functionality multi-party RTT > > presentation in one display area. Only one source at a time can be presented > > in real-time, but switch of source of text to display in real-time can be made > > automatically by the mixer and at suitable points in the text streams. Sources > > could be identified by inline text labels in IRC style. This presentation style > > does not meet all RTT requirements and if used, should be a temporary > > fallback method for conference-unaware clients." > > > > > > This wording is a self sustained description on what is possible and would > > also match better the recently revived work on multi-party rtt. > > > > > > Regards > > > > > > Gunnar > > > > > > > > > > > > Den 2019-11-06 kl. 17:29, skrev Christer Holmberg: > > > Bo, are you ok with the proposals? > > > > > > Regards, > > > > > > Christer > > > > > > > > > From: Gunnar Hellström mailto:gunnar.hellstrom@omnitor.se > > > Sent: Wednesday, November 6, 2019 5:16 PM > > > To: Christer Holmberg mailto:christer.holmberg@ericsson.com; Bo Burman > > > mailto:bo.burman=40ericsson.com@dmarc.ietf.org; mmusic > > > (mailto:mmusic@ietf.org) mailto:mmusic@ietf.org > > > Cc: 'mailto:mmusic-chairs@tools.ietf.org' > > > mailto:mmusic-chairs@tools.ietf.org > > > Subject: SV: [MMUSIC] Starting shepherd's review of > > > draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments > > > > > > Christer, > > > I agree with your proposals. > > > > > > Regards > > > Gunnar > > > > > > ---------------------------------------------------------------------- > > > Gunnar Hellström > > > Omnitor > > > mailto:gunnar.hellstrom@omnitor.se > > > +46 708 20 42 88 > > > > > > Från: Christer Holmberg mailto:christer.holmberg@ericsson.com > > > Skickat: den 6 november 2019 09:58:30 > > > Till: Gunnar Hellström mailto:gunnar.hellstrom@omnitor.se; Bo Burman > > > mailto:bo.burman=40ericsson.com@dmarc.ietf.org; mmusic > > > (mailto:mmusic@ietf.org) mailto:mmusic@ietf.org > > > Kopia: 'mailto:mmusic-chairs@tools.ietf.org' > > > mailto:mmusic-chairs@tools.ietf.org > > > Ämne: Re: [MMUSIC] Starting shepherd's review of > > > draft-ietf-mmusic-t140-usage-data-channel-07 - Bo's technical comments > > > > > > Hi, > > > > > > --- > > > 3) In section 4.2.1, it says that “If the 'fmtp' attribute is not included, it > > indicates that no maximum character transmission rate is indicated. It does > > not mean that the default value of 30 applies”; >why is this deviation from > > RFC 4103 chosen? Does it introduce a risk for interoperability problems with > > systems that also doesn’t use fmtp but interprets it as maximum 30 cps? > > > Gunnar? > > > [GH] I don't know why this deviation was chosen. But I have not > > commented it. You are right that it may introduce an increased risk for > > interoperability problems. But RFC 4103 has a precaution. In chapter 6, where > > the cps is introduced, it is said: > > > " > > > receivers of text/t140 MUST be designed so they can handle temporary > > > reception of characters at a higher rate than this parameter > > > specifies. As a result malfunction due to buffer overflow is avoided > > > for text conversation with human input." > > > > > > (the reason for this note is for backward compatibility with RFC 2793, > > > the obsoleted predecessor of RFC 4103, so it is not exactly our case, but still > > valid.) We have discussed the risk that implementations may not implement > > setting or reading the dcsa attributes because of the complexity to do so > > alongside with the WebRTC API. That situation may cause a situation where a > > sent cps parameter is not obeyed. So the case is quite similar to the case in > > RFC 4103, and applications would be required to prepare for handling > > temporary reception at high rates. > > > The intention of T.140 is to handle real-time text conversation between > > humans. Huge cut and paste chunks of text cannot be required to be > > handled rapidly. The highest speed human interaction would be with speech- > > to-text applications. A very rapid speaker may produce 200 words per > > minute. That is 17 characters per second. The speech-to-text applications > > often makes corrections by long backspaces and resendings. That may add 10 > > characters per second in the total. That results in a practical need of up to 27 > > characters per second for one stream. > > > This calculation shows that for two-party calls, it would not hurt to use the > > same convention regarding cps default as RFC 4103 (30). > > > For centralized conference solutions with just one data channel from the > > conference server discussed in section 5.5, the need would be a multiple of > > that rate (27) corresponding to the number of simultaneous text senders. In > > well managed conferences this multiple is very close to one. > > > The figures above are extremes. Currently most use of RTT is typing at > > maximum speeds of about 7 characters per second. > > > Leaving the default to unrestricted might attract some misuse by > > implementations or users trying to use the T.140 data channel for data > > transmission of data totally different from the intended real-time text. > > > Conclusion after all this discussion: > > > Neither leaving the default to unlimited, nor changing to a default of 30 cps > > as in RFC 4103 seems very critical. Any solution will do. > > > > > > [Christer] I am pretty sure IESG would ask about this too, I suggest that we > > change the default to 30 cps. > > > > > > --- > > > 5) In section 5.5, in the note, it says ‘…with limitations in real-time > > performance and presentation style’; I think it would be helpful to briefly > > elaborate on what type of limitations would be >expected and why. > > > I think it is explained in the other text of the section. For example, using a > > single data channel without any protocol extensions would not allow to > > separate the sources etc. > > > [GH] I think we can offer a bit more text at the end of the note to clarify. > > How about this: > > > "T.140 shows two examples of presentation layout for real-time text, one > > being column oriented, with one column per participant, another being > > arranged in one column with labels identifying the beginning of text from > > each participant and text from a number of participants received and placed > > in places corresponding to these different participants. With a conference > > mixer using one text stream and not applying any presentation protocol > > extension would only be able to produce a string for presentation in one > > column, including a source label in the beginning of text from one participant > > and only show text in real time from one participant at a time, shifting real- > > time presented participant at suitable points in the text stream. (end of > > phrase, end of sentence, line separator, long delay etc.). This presentation > > style may not be preferred by the user and it may cause delay before > > presentation of text from other than the currently presenting participant." > > > Pew, maybe too long and detailed.... > > > > > > [Christer] Or, could we simply remove the last sentence ("Conference > > mixers that...")? The 1st paragraph already says why separate channels are > > needed, and the note says that future extensions may allow usage of a single > > channel, so I think it is pretty clear that using a single channel without any > > such extensions would come with limitations. > > > > > > --- > > > > > > 6) In section 6, bullet “If the gateway detects or suspects loss of data on the > > RTP stream…”; shouldn’t it await possible redundancy first and missing text > > marker is inserted only when the used >redundancy is not capable to repair > > the loss? > > > Gunnar? > > > [GH]The intention was that it would mean "after using possibly received > > redundant data". You could interpret "loss of data" to mean that (instead of > > "loss of packets"), but let me try an improvement: "If the gateway detects or > > suspects loss of data on the RTP stream, after use of possibly received > > redundant data, …" > > > > > > [Christer] What about? > > > > > > > > > "If the gateway detects or suspects loss of data on the RTP stream, and the > > lost data has not been retrieved using a redundancy mechanism, the > > gateway SHOULD insert the T.140 missing text marker [T140ad1] in the data > > sent on the outgoing T.140 data channel." > > > --- > > > > > > 12) In section 11.1, in the [T140ad1] reference, is “aEUR” really part of the > > name? The name I find listed on the ITU-T web is “ITU-T T.140 (1998) Add. 1 > > (02/2000)”, and the title in the document >itself seems to be “Protocol for > > multimedia application text conversation; Addendum 1”. > > > Interesting. There is no "aEUR" in the XML file, so this seems to be > > something created by XML2RFC. > > > > > > The intended title is: > > > > > > Recommendation ITU-T.140 – Addendum 1 (02/2000), "Protocol for > > multimedia application text conversation" > > > > > > I will fix it. > > > [GH] I chased a number of such occurrences earlier. I think it was because > > your editor inserted an unusual slanting quotation mark. Note that there is > > also a double quotation mark on the third line of the same reference. > > > > > > [Christer] I will double check. > > > > > > --- > > > > > > Regards, > > > > > > Christer > > > > > > > > -- > > > > + + + + + + + + + + + + + + > > > > Gunnar Hellström > > Omnitor > > gunnar.hellstrom@omnitor.se<mailto:gunnar.hellstrom@omnitor.se> > > +46 708 204 288 > > > -- + + + + + + + + + + + + + + Gunnar Hellström Omnitor gunnar.hellstrom@omnitor.se<mailto:gunnar.hellstrom@omnitor.se> +46 708 204 288 -- + + + + + + + + + + + + + + Gunnar Hellström Omnitor gunnar.hellstrom@omnitor.se<mailto:gunnar.hellstrom@omnitor.se> +46 708 204 288
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg
- Re: [MMUSIC] Starting shepherd's review of draft-… Gunnar Hellström
- Re: [MMUSIC] Starting shepherd's review of draft-… Gunnar Hellström
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg
- Re: [MMUSIC] Starting shepherd's review of draft-… Gunnar Hellström
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg
- Re: [MMUSIC] Starting shepherd's review of draft-… Gunnar Hellström
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg
- Re: [MMUSIC] Starting shepherd's review of draft-… Gunnar Hellström
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg
- Re: [MMUSIC] Starting shepherd's review of draft-… Gunnar Hellström
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg
- Re: [MMUSIC] Starting shepherd's review of draft-… Gunnar Hellström
- Re: [MMUSIC] Starting shepherd's review of draft-… Bo Burman
- Re: [MMUSIC] Starting shepherd's review of draft-… Bo Burman
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg
- Re: [MMUSIC] Starting shepherd's review of draft-… Bo Burman
- Re: [MMUSIC] Starting shepherd's review of draft-… Gunnar Hellström
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg
- Re: [MMUSIC] Starting shepherd's review of draft-… Gunnar Hellström
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg
- Re: [MMUSIC] Starting shepherd's review of draft-… Christer Holmberg