Re: [xrblock] Adam Roach's No Objection on draft-ietf-xrblock-rtcweb-rtcp-xr-metrics-09: (with COMMENT)
Ben Campbell <ben@nostrum.com> Thu, 24 May 2018 19:26 UTC
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Date: Thu, 24 May 2018 14:26:33 -0500
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To: "draft-ietf-xrblock-rtcweb-rtcp-xr-metrics@ietf.org" <draft-ietf-xrblock-rtcweb-rtcp-xr-metrics@ietf.org>, "Huangyihong (Rachel)" <rachel.huang@huawei.com>
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Subject: Re: [xrblock] Adam Roach's No Objection on draft-ietf-xrblock-rtcweb-rtcp-xr-metrics-09: (with COMMENT)
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Hi, It looks like the discussion on Adam’s comments have reached resolution, and I think that is also mostly true for the other IESG comments. Authors; Please submit a new revision when you are ready. Thanks! Ben. > On May 21, 2018, at 10:20 PM, Adam Roach <adam@nostrum.com> wrote: > > Thanks! Your proposed resolutions look good to me. > > /a > > On 5/21/18 10:18 PM, Huangyihong (Rachel) wrote: >> Hi Adam, >> >> Thanks for the comments. Please see inline. >> >> BR, >> Rachel >> >>> -----Original Message----- >>> From: Adam Roach [mailto:adam@nostrum.com] >>> Sent: Tuesday, May 22, 2018 8:56 AM >>> To: The IESG >>> Cc: draft-ietf-xrblock-rtcweb-rtcp-xr-metrics@ietf.org; Shida Schubert; >>> xrblock-chairs@ietf.org; shida.at.ietf@gmail.com; xrblock@ietf.org >>> Subject: Adam Roach's No Objection on >>> draft-ietf-xrblock-rtcweb-rtcp-xr-metrics-09: (with COMMENT) >>> >>> Adam Roach has entered the following ballot position for >>> draft-ietf-xrblock-rtcweb-rtcp-xr-metrics-09: No Objection >>> >>> 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-xrblock-rtcweb-rtcp-xr-metrics/ >>> >>> >>> >>> ---------------------------------------------------------------------- >>> COMMENT: >>> ---------------------------------------------------------------------- >>> >>> Thanks to the authors and contributors on this document. I have two >>> substantive >>> comments, and a handful of minor nits. >>> >>> --------------------------------------------------------------------------- >>> >>> §5.3.1: >>> >>>> application can use these metrics to calculate the Mean Opinion Score >>>> (MoS) values or Media Delivery Index (MDI) for their services. >>> "...calculate Estimated Mean Opinion Score (eMOS) values..." >>> >>> (MOS scores necessarily require human subjective evaluation of audio under >>> carefully controlled circumstances -- any computer-generated metrics are >>> inherently estimations, and should not be called MOS scores.) >>> >> [Rachel]: You're right. Will change to "estimated Mean Opinion Score (MOS)" in the next version. >> >>> --------------------------------------------------------------------------- >>> >>> §5.3.1: >>> >>>> Error-resilience mechanisms, like RTP retransmission or FEC, are >>>> optional in RTCWEB because the overhead of the repair bits adding to >>>> the original streams. >>> This is a little misleading. draft-ietf-rtcweb-rtp-usage says: >>> >>> WebRTC endpoints MUST follow the recommendations for FEC use given in >>> [I-D.ietf-rtcweb-fec]. >>> >>> And, in turn, draft-ietf-rtcweb-fec says: >>> >>> To support the functionality recommended above, implementations MUST >>> be able to receive and make use of the relevant FEC formats for their >>> supported audio codecs, and MUST indicate this support, as described >>> in Section 4. Use of these formats when sending, as mentioned above, >>> is RECOMMENDED. >>> >>> Rather than trying to reiterate this somewhat nuanced situation in *this* >>> document, I recommend removing the entire sentence and fixing the rest of >>> the >>> paragraph. If you choose to keep it, please make sure it more clearly explains >>> the level of FEC support required of RTCWEB implementations. >>> >> [Rachel]: Your concern makes sense to me. I'll delete it as following: >> >> OLD >> >> " >> Error-resilience mechanisms, like RTP retransmission or FEC, are >> optional in RTCWEB because the overhead of the repair bits adding to >> the original streams. But they do help to greatly reduce the impact >> of packet loss and enhance the quality of transmission. Web >> applications could support certain repair mechanism after negotiation >> between both sides of browsers when needed. >> " >> >> NEW >> " >> Web applications could support certain RTP error-resilience mechanisms following the recommendations specified in [draft-ietf-rtcweb-rtp-usage]. >> " >> >>> ================================================================ >>> =========== >>> >>> The remainder of my comments are grammatical or editorial nits that should >>> be >>> fixed before progressing the document. >>> >>> --------------------------------------------------------------------------- >>> >>> §3: >>> >>>> The RTCP Sender Reports (SRs) and Receiver Reports (RRs) [RFC3550] >>>> exposes the basic metrics... >>> "expose" >>> >>>> However, these metrics provides... >>> "provide" >>> >>> >>>> For example, it may be useful to distinguish between >>>> packets lost and packets discarded due to late arrival, even though >>>> they have the same impact on the multimedia quality, it helps in >>>> identifying and diagnosing issues. >>> This is a run-on sentence. Suggest: "...due to late arrival. Even though..." >>> >>>> The WebRTC application extracts the statistic from the browser by >>>> querying the getStats() API [W3C.WD-webrtc-20161124], but the browser >>>> currently only reports the local variables i.e., the statistics >>>> related to the outgoing RTP media streams and the incoming RTP media >>>> streams. >>> I don't think the "currently" in this sentence is actually true any longer; and >>> I expect it to get increasingly less true as time goes on. Consider rephrasing. >>> >>>> [I-D.ietf-rtcweb-rtp-usage] does not mandate the use of >>>> any RTCP XRs and since their usage is optional. >>> This is not a sentence. Maybe remove "since"? >>> >>> --------------------------------------------------------------------------- >>> >>> §4: >>> >>>> For example, an application may choose >>>> to poll the stack for statistics every 1 second, in this case the >>>> underlying stack local will return the current snapshot of the local >>>> statistics (for incoming and outgoing media streams). >>> This is a comma splice. Consider: "...every second. In this case..." >>> >>>> However it may >>>> return the same remote statistics as before for the remote >>>> statistics >>> Add a comma after "However". >>> >>> --------------------------------------------------------------------------- >>> >>> §5: >>> >>>> Since following metrics are all defined in RTCP XR which is not >>>> mandated in WebRTC, all of them are local. >>> "Since the following..." >>> ^^^ >>> >>> "...RTCP XR, which is..." >>> ^ >>> >>>> However, if RTCP XR is >>>> supported by negotiation between two browsers, following metrics can >>>> also be generated remotely and be sent to local by RTCP XR packets. >>> "...two browsers, the following..." >>> ^^^ >>> >>>> Following metrics are classified into 3 categories: network impact >>> "The following metrics..." >>> ^^^ >>> >>> >>>> viewpoint of application, e.g., bit rate, frames rate or jitter >>> "...frame rate..." >>> >>>> WebRTC >>>> application can use these metrics to calculate the Mean Opinion Score >>> "applications" >>> >>> >>> --------------------------------------------------------------------------- >>> >>> §5.1.1: >>> >>>> lost and duplicated packets. Lost packets counts are useful for >>> "Lost packet counts..." >>> >>> --------------------------------------------------------------------------- >>> >>> §5.1.3: >>> >>>> the two run length vectors to identify congestion-related losses, >>>> i.e., a router queue became overloaded causing delays and then >>> Replace "i.e." ("that is") with "e.g." ("for example"). >>> >>> --------------------------------------------------------------------------- >>> >>> §5.2.1: >>> >>>> The metric reports the cumulative size of the packets discarded in >>>> the interval, it is complementary to number of discarded packets. >>> "...the interval. It is complementary..." >>> >>> --------------------------------------------------------------------------- >>> >>> §5.2.2: >>> >>>> For >>>> audio streams, a single RTP packet may contain one or multiple audio >>>> frames, each of which has a fixed length. >>> I don't think this is generally true. Even in the case of WebRTC, I believe the >>> default mode of operation for Opus is VBR, which results in frame sizes that >>> vary from frame to frame. >>> >>>> The metrics in this category includes: number of discarded key >>> "...category include:..." >>> >>> --------------------------------------------------------------------------- >>> >>> >>> §5.3.1: >>> >>>> The un-repaired packets count and repaired loss count defined in >>> "...unrepaired packet count..." >>> >>>> packets to lost packets. Including this kind of metrics helps the >>> Choose either "...these kinds of metrics..." or "...this kind of metric..." >>> >>> --------------------------------------------------------------------------- >>> >>> §5.3.2: >>> >>>> related losses, i.e., a router queue became overloaded causing delays >>> Replace "i.e." with "e.g." >>> >>> --------------------------------------------------------------------------- >>> >>> §6: >>> >>>> identifiers relevant to RTP media in WebRTC. These group of >>>> identifiers are defined on a ReportGroup corresponding to an >>>> Synchronization source (SSRC). In practice the application need to >>> "This group of identifiers..." >>> ^^^^ >>> >>> "...corresponding to a synchronization source..." >>> ^ >>> >>> "...the application needs to..." >>> ^^^^^ >>> >>>> For XR metrics, it depends on >>>> two factors: 1) if it measured at the endpoint, 2) if it reported by >>>> the endpoint in an XR report. >>> "...if it is measured..." >>> ^^ >>> >>> "...if it is reported..." >>> ^^ >>> >>> --------------------------------------------------------------------------- >>> >>> §11.2: >>> >>>> [W3C.WD-webrtc-20161124] >>>> Sporny, M. and D. Longley, "WebRTC 1.0: Real-time >>>> Communication Between Browsers", World Wide Web >>> Consortium >>>> WD WD-webrtc-20161124, November 2016, >>>> <https://www.w3.org/TR/2016/WD-webrtc-20161124>. >>> The authorship of this document is incorrect (neither Sporny nor Longley are >>> authors on WebRTC). >>> >>> The URL points to an outdated version of the specification. Please update to >>> https://www.w3.org/TR/2017/CR-webrtc-20171102/ >>> >>> >>>> [W3C.WD-webrtc-stats-20161214] >>>> Alvestrand, H. and V. Singh, "Identifiers for >>>> WebRTC's Statistics API", World Wide Web Consortium >>>> WD WD-webrtc-stats-20161214, December 2016, >>>> <https://www.w3.org/TR/2016/WD-webrtc-stats-20161214>. >>> Please replace "'" with an apostrophe. >>> >>> Please update the URL to >>> https://www.w3.org/TR/2018/WD-webrtc-stats-20180519/ >>> >> [Rachel]: They'll be fixed in the next version. Thanks. > >
- [xrblock] Adam Roach's No Objection on draft-ietf… Adam Roach
- Re: [xrblock] Adam Roach's No Objection on draft-… Adam Roach
- Re: [xrblock] Adam Roach's No Objection on draft-… Huangyihong (Rachel)
- Re: [xrblock] Adam Roach's No Objection on draft-… Adam Roach
- Re: [xrblock] Adam Roach's No Objection on draft-… Ben Campbell
- Re: [xrblock] Adam Roach's No Objection on draft-… Huangyihong (Rachel)