[lp-wan] Shepherd review of draft-ietf-lpwan-schc-over-nbiot-09.txt

["Pascal Thubert (pthubert)" <[e-mail]>]

Dear authors and all:

Many thanks for this great document! 

I find it well-written and very informative, though a few sentences should be re-edited. In particular, the drawings in section 4.2 are just great.

In prep for publication please find my review for draft-ietf-lpwan-schc-over-nbiot-09, can you please consider the following suggestions and publish a version 10:

1) Terminology: missing  Requirements Language (BCP 14) - please add, see example in the Yang model draft.

2) Terminology: define PLMN; also NGW-SGW is defined but the figure uses NGW-CSGW: please align.

3) References: make but RFC 8724, RFC 8376, RFC 2119, and RFC 8174 normative references; and move all other references to the informative reference section - unless this document cannot be implemented without details specified the reference.

4) References: typo in the title of TR33203. Also add references to OMA and OneM2M

5) "The signaling data uses a different path with specific protocols". The use of "data" while understandable could be misleading since we usually associate with user data as opposed to signaling data; so maybe saying signaling without saying data is more readable, or "control signaling" as you do elsewhere in the document? Also, is it the same signaling as in the previous sentence or is this one not in band? I got confused.  

6) "The maximum recommended 3GPP MTU size is 1358 Bytes." Should we make that the IPv6 MTU for the link that SCHC provides in the UE? Should we say that the IPv6 min MTU of 1280 is always to be used in SCHC over NB IOT links like 6LoWPAN does? 

7) "The SCHC functionalities can only be used over the radio transmission between the Dev-UE and the RGW-eNB. ". Do you mean: "In one form of deployment, the SCHC functionalities may be used over the radio transmission between the Dev-UE and the RGW-eNB only"? Note that though I try and have a feeling of what you mean to say, I cannot really parse the rest of the paragraph. Please consider rewriting the whole paragraph for clarity; possibly indicating where the SCHC GW is positioned. Please add references to the next sections where the cases are discussed in more details (like say "more in ..." or "see .. for more").

8) section " 4.1.  Use of SCHC over the Radio link ". I understand that the constraints of the radio link apply even if the SCHC GW is located further down in the core, correct? So most of the text in that section is generic.

9) "However, given the case in the future, SCHC fragmentation may be used.  " does not parse either.

10) " The Appendix gives more details". This formulation or similar is used without a link to the section in the appendix where the additional information is given. A forward link would be useful.

11) " 4.2.1.  SCHC Entities Placing" title is half informative. Maybe add " in the SCHC over NAS case" or something?

12)  In this scenario, SCHC may reside in the Non-Access Stratum (NAS) protocol layer.  "
why "may" ? I thought the whole section 5.2 is a about this? So it just does not may do, correct?

13) " Because the NAS protocol already uses RoHC it can adapt SCHC for header compression too. ". Please rephrase. Who is it? what adaptation is needed? Or do you mean use/adopt?

14) " SCHC for IoT applications MUST be considered to improve the device's ". This seems to indicate what 3GPP MUST do. Certainly you mean something else? Please rephrase.

15) "SCHC Context initialization RRC (Radio Resource Control)". Aren't you missing a ":" sign? The whole item is unreadable without it, true for all the next listed items.

16) "Implying that" -> "This implies"; " might use provision sets": Might? What if not?

17) " The minimum physical" -> "The smallest physical" otherwise you have different minimum values.

18) Since a TB of 88bits has very little room for SCHC, is that room enough to ensure that " SCHC overhead should not exceed the available number of effective bits of the smallest physical TB available "? How should we read that "should" written in lowercase? Do you mean that it is preferable? Is it a MUST? What happens if not?


19) 4.2.2. applied to 4.1 and 4.2 so it is weirdly placed. Maybe it should be 4.3? also the title seems to be missing "cases" in the end. Note my remark on 4.1.1 where the same is mostly true as well.

20) 4.3.2, same comment on the listed items that we're missing ":" though in some cases there is a "."

21) "capillarity gateway" -> "capillary gateway"

22) " mode is even desirable ": what do you mean by "even" ?

23) " is recommended": lowercase? Also a formulation like " WINDOW_SIZE is recommended to be 2^N-1. " (multiple cases) feels strange. Whazt about " a WINDOW_SIZE of 2^N-1 is RECOMMENDED. "

24) "Table 10.5.163a in {3GPP-TS_24.088}": Link failure, probably an issue with the source markup.



Voila! Many thanks for the appendices as well, they are really useful. Please make sure they remain in the final version.

Keep safe;

Pascal (shepherd hat on)