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

From: "Ali Sajassi (sajassi)" <[email-masked]>
Date: Mon, 31 Aug 2020 22:25:04 +0000

Hi Eric,

Thanks for your review and your comments, please refer to my replies inline marked with [AS].

On 7/14/20, 5:32 AM, "Éric Vyncke via Datatracker" <[email-masked]> wrote:

    Éric Vyncke has entered the following ballot position for
    draft-ietf-bess-evpn-inter-subnet-forwarding-09: No Objection

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    ----------------------------------------------------------------------
    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).

[AS] the above quoted text is provided as an example and it should be clear enough
Without making the sentence to verbose. 

    -- 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.

[AS] I don't think the IRB interface MAC address in the initial ARP reply can be used 
In RA because it is a multicast packet - i.e., the MAC address of old IRB interface and the
New IRB interface cannot be sent in a single multicast packet.

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

[AS] Done.

    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] Done.

    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)."

[AS] for IPv6, the NLRI has 12 additional bytes.

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

[AS] Done.

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

AS] Done.

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

[AS] Done.

    -- 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 ;-)

[AS] yes, the quoted sentence already exist. 

    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?

[AS] duplicate MACs are covered in RFC 7432.

    == 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).

[AS] Added clarification that "subnet" means "IP subnet".