Re: [Bier] John Scudder's No Objection on draft-ietf-bier-evpn-11: (with COMMENT)

["Jeffrey (Zhaohui) Zhang" <[e-mail]>]

Hi John,

Thanks for your review and comments! I posted the -12 revision that address comments from you, Warren, and Zaheduzzaman: https://author-tools.ietf.org/iddiff?url1=draft-ietf-bier-evpn-11&url2=draft-ietf-bier-evpn-12&difftype=--html

Please see zzh> below for some clarifications. If I don't say anything about a comment, it means it's been fixed as you suggested.


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COMMENT:
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# John Scudder, RTG AD, comments for draft-ietf-bier-evpn-11 CC @jgscudder

Thanks for this document. As usual with multicast documents, I largely am taking it on faith that the authors and WG know what they're doing, but I still have a few non-blocking comments, below.

## COMMENTS

### Section 1.1

- You define "AC", but only use it once, IMO the definition isn't needed in this case (for that matter the abbreviation isn't needed in Section 2.2.2.1, you can just use your words).

- "Sets of C-flows can be identified by the use of the "C-*" wildcard" -- I wonder if "denoted" would be a better term than "identified" in this context.

- "A multicast tunnel through the network of one or more SPs" -- presumably by "SPs" you mean "service providers". Probably better to write it out.

### Section 2.2.1

I can't understand what this sentence means: "Only when selectively forwarding is for all flows without tunnel segmentation, SMET routes are used without the need for S-PMSI A-D routes." Specifically, I can't parse the first clause. I would propose a rewrite if I had a solid guess as to what it meant, but alas.

Zzh> Perhaps adding an "and" would help? "Only when selectively forwarding is for all flows *and* without tunnel segmentation" - if selective forwarding is used only for some flows, or if tunnel segmentation is used then we have to use S-PMSI routes together with SMET routes.

### Section 2.2.2.1

I'm guessing that when you write, "It may be desired that SMET routes are not used to reduce the burden of explicit tracking", what you mean is "It may be desired that SMET routes are not used, in order to reduce the burden of explicit tracking"?

Zzh> Yes.

(See also https://urldefense.com/v3/__https://en.wikipedia.org/wiki/Eats,_Shoots_*26_Leaves__;JQ!!NEt6yMaO-gk!BvDIszB2LMoegy8Nm-CGMImTzct3kwWAjkELszv8ZDt5m7EwRHJaIA22y8L-DGErmA1xx8CN7filEx4$ )

### Section 3

Please expand "DF".

### Section 4.1.1, best match

I trust/hope that other documents in the BIER/EVPN/MVPN set clearly define what "best match" means in this context. It's not intuitively obvious what things like "best match the source and destination IP address" mean, absent a definition.

Zzh> The SMET and S-PMSI route all have source/group address fields. The match is based on that. I added "whose source and group address fields".

### Section 4.1.2

"Each instance of the re-advertised route for a downstream region has a PTA that specifies tunnel information that is the same as or different from that of the route for a different region."

Possibly this is just my lack of expertise in the subject area and appreciation for your subtlety, but I don't see how the second half of the sentence conveys any information. Couldn't you rewrite it as "Each instance of the re-advertised route for a downstream region has a PTA."?

Zzh> I guess I was just trying to say that the tunnel information for different downstream regions may be different or the same. I see your point - I changed it to "... a PTA that specifies the tunnel for that region."

Thanks!
Jeffrey

## Notes

This review is in the ["IETF Comments" Markdown format][ICMF], You can use the [`ietf-comments` tool][ICT] to automatically convert this review into individual GitHub issues.

[ICMF]: https://urldefense.com/v3/__https://github.com/mnot/ietf-comments/blob/main/format.md__;!!NEt6yMaO-gk!BvDIszB2LMoegy8Nm-CGMImTzct3kwWAjkELszv8ZDt5m7EwRHJaIA22y8L-DGErmA1xx8CNXrwcMOA$
[ICT]: https://urldefense.com/v3/__https://github.com/mnot/ietf-comments__;!!NEt6yMaO-gk!BvDIszB2LMoegy8Nm-CGMImTzct3kwWAjkELszv8ZDt5m7EwRHJaIA22y8L-DGErmA1xx8CNf-0Wo80$