Re: [Mops] AD review of draft-ietf-mops-ar-use-case-14

[Renan Krishna <[e-mail]>]

Hi Eric,

Many Thanks for your review. We have folded in your comments in "-15". Please see our replies/actions in detail inline below.

Regards,
Renan 

-----Original Message-----
From: Eric Vyncke (evyncke) <evyncke=[e-mail]> 
Sent: Friday, January 5, 2024 4:41 PM
To: [e-mail]; Renan Krishna <[e-mail]>; [e-mail]
Cc: [e-mail]
Subject: AD review of draft-ietf-mops-ar-use-case-14

Hello and Happy New Year,

As usual, I have done my AD review of draft-ietf-mops-ar-use-case-14 before processing with the publication process (i.e., IETF Last Call).

All the comments (except when noted otherwise) must be either replied to (and feel free to disagree with me of course) or acted upon (e.g., with new text).

# Shepherd's write-up

For Stephan (the shepherd), the shepherd’s write-up would benefit if the answers were clearly delineated from the questions. Else, I find the shepherd well written, thank you.

# Generic

The I-D has many typos in it and uses wrong punctuation marks (e.g., no space char after a comma or a dot, or missing a comma after lead complement, or missing a '-' between two words), please use a spell checker (for your convenience, I have attached a MS-Word copy of the I-D so you can use Word spell checkers).
>Renan: Fixed

The text often uses ‘we’, and this is quite unusual for an IETF documents. Consider rephrasing all sentences having “we”.
>Renan: Rephrased all the sentences having "we"

# Abstract

`different form factors`, unsure whether it is the right term here (my non-English reading assumes physical format).
>Renan: Added: '(such as different physical sizes and shapes)'

# Section

`Reality` or `Realty` ?
> Renan: Fixed

# Section 1

Some middle parts are 'hand waving', e.g., unsure what SDN has to do here as in `with open interfaces using SDN`.
> Renan: rephrased as: '(using SDN to break vertically integrated systems into independent components- these components can have open interfaces which are standard, well documented and not proprietary)'

# Section 2

Consider removing section 2 as there is no normative language in the I-D (usual for an informative I-D) and the template is the old one.
>Renan: Removed section 2

`Such techniques enable XR applications requiring low-latency and high bandwidth to be delivered by mini-clouds running on proximate edge devices` really looks like a marketing statement. Consider adding justification (with references) or removing it.
>Renan: added the justification with reference: 'This is because the disaggregated components can run on proximate edge devices rather than on remote cloud several hops away and deliver low latency, high bandwidth service to offloaded applications [EDGE_2].'

Unsure what `GPS` is doing here... Also, do not use "GPS" as it is a commercial offering by a US company, let's be global and GNSS (global navigation satellite systems).
>Renan: Modified to: 'location sensing capabilities using systems such as a global navigation satellite system (GNSS) are another example of such devices.'

Please explain ` heavy-tailed` in this context.
>Renan: Added: 'Heaviness of tails is defined as the difference from the normal distribution in the proportion of the values that fall a long way from the mean [HEAVY_TAIL_3].'

Please expand "QoE" at first use.
> Renan: Added 'Quality Of Experience (QoE)'

# Section 3

This section is about AR while the I-D is about XR. Suggest to rename the document.
>Renan: Replaced 'AR' with 'XR' as the use case has elements of both AR and VR. So, we have used the more general term XR which subsumes both AR and VR in the new '-15' version.

# Section 3.1

Please explain ` annotated point cloud based model` to the reader.
>Renan: Added 'annotated point cloud (a set of points in space that are annotated with descriptors)'

You may also expand 2D, 3D, 5D, ... in a generic way (and for myself, I have no clue what 5D represents).
>Renan: Rephrased as: 'Such a 2D lightfield is stored as a two-dimensional table. Assuming distant light sources, the single point is approximately valid for small scenes. For larger scenes, many 3D positions are additionally stored making the table 5D [AUGMENTED].'

# Section 4

The section title "requirements" only vaguely relates to the first paragraph (i.e., "Technical challenges and solutions" would be better) *and* do not really fit the 2nd paragraph, which is more about solution/workaround.
>Renan: Renamed the section as "Technical challenges and Solutions"

Has " 360 degree streaming" been defined before ?
>Renan: Added:' 360 degree streaming (streaming of video that represents a view in every direction in 3D space) '

`the 3GPP requires and supports an Ultra Reliable Low Latency` while the 3GPP reference is only a study and not a specification.
>Renan: Rephrased as 'Towards this end, a 3GPP study indicates an Ultra Reliable Low Latency of 0.1ms to 1ms for communication between an Edge server and User Equipment (UE) [URLLC].'

Is there any justification for the assertion ` This is because with such distributions, law of large numbers works too slowly, the mean of sample does not equal the mean of distribution,`?
>Renan: Added the appropriate references: 'This is because with such distributions, law of large numbers works too slowly [HEAVY_TAIL_2], the mean of sample does not equal the mean of distribution [HEAVY_TAIL_2], and as a result standard deviation and variance are unsuitable as metrics for such operational parameters [HEAVY_TAIL_1].'

# Section 5.1

`parameters that capture the characteristics of XR application behavior are heavy-tailed` but the section title is about "AR" ?
>Renan: Replaced 'AR' by 'XR' in the section title

The term ` UE device` is more suitable for a 3GPP document, for IETF suggest to use "user device".
> Renan: Replaced 'UE' by 'user device'

Is there a previous definition of ` 6DoF`?
>Renan: expanded 6DoF to '6 degrees of freedom (6DoF)'

The 2nd paragraph has many assertations without any reference or justification.
> Renan: Added references and rephrased throughout 2nd paragraph.

# Section 5.2

Is `when operationalizing a network` correct English ?
> Renan: Yes, according to Oxford Online dictionary 😊

s/ The following issues were identified.:/ The following characteristics were identified:/ ?
>Renan: Changed to: ' The following characteristics were identified:'

I would refrain using a 2002 reference for ` The packet loss rates in wireless links between XR devices and the Edge server can be as high as 2% or more [WIRELESS_1].` and the actual current number is probably better. I.e., this paragraph can probably be removed.
>Renan: removed.

I do not see a matching row in table 2 for the assertion `the required bandwidth for our use case as discussed in section 5.2 is 200Mbps-1000Mbps`.
> Renan:  corrected to ' as discussed in section 5.1, Table 1,'

# Section 8

Oxford comma is probably required in the list of names.
>Renan: Agreed, changed to Oxford comma.