Subject: [bess] Éric Vyncke's No Objection on draft-ietf-bess-evpn-inter-subnet-forwarding-09: (with COMMENT)

From: Éric Vyncke via Datatracker <[email-masked]>
Date: Tue, 14 Jul 2020 05:32:45 -0700

Éric Vyncke has entered the following ballot position for
draft-ietf-bess-evpn-inter-subnet-forwarding-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-bess-evpn-inter-subnet-forwarding/

----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------

Thank you for the work put into this document.

Please find below a couple of non-blocking COMMENTs (and I would appreciate a
reply to each of my COMMENTs).

I hope that this helps to improve the document,

Regards,

-éric

PS: as a side note, I found that this document uses too many acronyms even for
short words (e.g., "SN" instead of "Subnet"). There are also very long
sentences that, when combined with acronyms, make reading difficult.

== COMMENTS ==

-- Section 2 --
About "to bridge non-IP and intra-subnet traffic and to route inter-subnet IP
traffic": suggest to clarify the text when the IP-VRF is IPv6 only, then, (I
assume) that IPv4 packets will be bridged and not IP-forwarded (and vice-versa).

-- Section 4.1 --
Suggest to replace "then the IRB interface MAC address MUST be the one used in
the initial ARP reply or ND Neighbor Advertisement (NA) for that TS." by "then
the IRB interface MAC address MUST be the one used in the initial ARP reply or
ND Neighbor Advertisement (NA) or Router Advertisement (RA) for that TS"
because routers MAC addresses are also advertised by Router Advertisements.

-- Section 5.1 --
Should also mention NDP when writing "(via an ARP request)" in the first
paragraph.

In the same vein, please add "NDP cache" to "Furthermore, it adds this TS's MAC
and IP address association to its ARP table".

As I am not an expert in EVPN, I am puzzled by the math about the Length field
"either 40 (if IPv4 address is carried) or 52 (if IPv6 address is carried)."

-- Section 5.2 --
This section also only mentions IPv4 ARP table, please add IPv6 NDP cache.

-- Section 6.1 --
Same comments as for section 5.1

-- Section 6.2 --
Same comments as for section 5.2

-- Section 7 --
Good to state "Although the language used in this section is for IPv4 ARP, it
equally applies to IPv6 ND."; even if I would have preferred to use by default
IPv6 ND ;-)

Please note that in IPv6 there are often at least TWO IPv6 addresses per MAC
(one link-local fe80::... and one global); so, "In the following subsections,
it is assumed that the MAC and IP addresses of a TS have one-to-one
relationship (i.e., there is one IP address per MAC address and vice versa). "
is obviously never the case for IPv6. I understand that the rest of the
paragraph explains how to handle the case but it could be easier to treat IPv6
in a separate sentence.

-- Section 7.1 --
While about mobility, this section appears to be also applicable to Duplicate
Address Detection but is unclear on what to do when the same IP but different
MAC (i.e., an actual IP address collision). Or is it covered in other documents?

== NITS ==

-- Section 1 --
"BD and subnet are equivalent terms" while in the rest of the document "IP
subnet" is often used. If "subnet IP" and "subnet" are synonyms, then I suggest
to keep using one for consistency or at least mention that "IP subnet" and
"subnet" are the same concept (or explain the difference if they are not
identical).