Re: [Bier] early AD review of draft-ietf-bier-ospf-bier-extensions-07

["Acee Lindem (acee)" <[e-mail]>]

Hi Alia,

I spoke to Peter and I think the OSPFv3 Bier Extensions should go into a separate OSPFv3 draft. Heretofore, all the work has been done in the BIER working group and it seems it would make sense to do it here rather than mix much into the overflow draft. As for the OSPF WG, the priority needs to be to publish the OSPFv3 Extended LSA draft. I’ll ask Abhay to start the WG last call and concurrently post the implementation information.

Thanks,
Acee

From: Alia Atlas <[e-mail]<mailto:[e-mail]>>
Date: Monday, October 2, 2017 at 2:32 PM
To: "Peter Psenak (ppsenak)" <[e-mail]<mailto:[e-mail]>>, Acee Lindem <[e-mail]<mailto:[e-mail]>>
Cc: "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, OSPF WG List <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: Re: early AD review of draft-ietf-bier-ospf-bier-extensions-07



On Mon, Oct 2, 2017 at 2:26 PM, Peter Psenak <[e-mail]<mailto:[e-mail]>> wrote:
Hi Alia,

please see inline:

On 02/10/17 17:33 , Alia Atlas wrote:
On Mon, Oct 2, 2017 at 11:07 AM, Peter Psenak <[e-mail]<mailto:[e-mail]>
<mailto:[e-mail]<mailto:[e-mail]>>> wrote:

    Hi Alia,

    please see inline:

    On 02/10/17 16:41 , Alia Atlas wrote:

        Hi Peter,

        On Mon, Oct 2, 2017 at 10:05 AM, Peter Psenak <[e-mail]<mailto:[e-mail]>
        <mailto:[e-mail]<mailto:[e-mail]>>
        <mailto:[e-mail]<mailto:[e-mail]> <mailto:[e-mail]<mailto:[e-mail]>>>> wrote:

             Hi Alia,

             please see inline:


             On 27/09/17 00:12 , Alia Atlas wrote:

                 I have done an early AD review of
                 draft-ietf-bier-ospf-bier-extensions-07 in preparation
        for the
                 publication request.

                 First, I would like to thank the many authors for their
        work on this
                 draft. Given that there are currently 7 authors listed, I'd
                 recommend
                 appointing a few editors or otherwise reducing down to 5 or
                 fewer. Of
                 course, I am also willing to consider extraordinary
                 circumstances where
                 the shepherd can explain to me privately the deep technical
                 contribution
                 made by each author.

                 I do see a number of major issues.

                 Major Issues:

                 1)  RFC7684 is just for OSPFv2.  How is the information
        carried for
                 OSPFv3? We need a mechanism that works for IPv6 also.


             BIER extension for OSPFv3 will be covered in a separate
        draft. It
             will be based on draft-ietf-ospf-ospfv3-lsa-extend draft.
        This is
             similar to what we did for SR and other extensions.


        I understand that theory - but I think it is getting less tractable.
        How far along is that draft? I'll need to at least
        reference it and discuss the IPv6 support in the write-up.  Once
        draft-ietf-ospfv3-lsa-extend is published as an RFC, I would really
        expect this to stop happening.


    given that the encoding of the OSPFv3 is way different to OSPFv2 and
    the fact that the draft-ietf-ospfv3-lsa-extend is still a work in
    progress I would tend to keep the v2 and v3 extensions separate.


Given the second, that's ok - but usually the difference in encoding
isn't enough to require a different draft.
Please do talk to Acee about this. He's collecting OSPFv3 LSA extensions
to add to a separate draft when
draft-ietf-osfpv3-lsa-extend progresses - and that draft is just waiting
on the implementations (and there are
finally 2 of them) so I expect it to move along soon.

    When you say "discuss the IPv6 support in the write-up" do you mean
    to mention it in draft-ietf-bier-ospf-bier-extensions? If yes, why?
    This documents only specifies OSPFv2 extension.


No - I mean in the shepherd's write-up - though an informative reference
to an OSPFv3 draft or a common one would help.  At the moment, there's
NOTHING about IPv6 and that's going to make it harder to get IESG
agreement on.

would stating in this document that OSPFv3 BIER extension will be covered in a separate draft help?

It would need more than that.  Let's see what Acee thinks is a reasonable approach.
My tendency would be to reference the draft that is collecting OSPV3 Extended LSA TLVs - but I'm not
sure if that draft is still merely conceptual.

        I don't know if you noticed that draft-ietf-sunset4-ipv6-ietf-01
        ("IETF:
        End Work on IPv4") is in IETF Last Call.
        Of course, it has lots of caveats and is getting a number of
        concerned
        comments - but the trend is obvious
        as is the deployment of IPv6 and the need for feature parity.


    not that I disagree, but let's not get into that discussion here :)


Just calling your attention to the current atmosphere :-)

                 2) In Sec 2.1, the Length is defined as variable and
        the figure
                 includes
                 additional sub-TLVs. Please clarify in the text what other
                 sub-TLVs can
                 be carried & how the length is calculated (yes, same as
        always - but
                 clarity helps with interoperability).


             will change to "Variable, dependent on sub-TLVs" language
        as we did
             in SR draft.


        Sounds good - Variable, 4 + length of sub-TLVs  I think.  I.e.,
        be clear
        on the length
        contributed by this TLV as well as the included sub-TLVs.


    not that I care too much, but I would like to keep the language same
    between documents. Unless you insist otherwise, keeping the
    "Variable, dependent on sub-TLVs" would make it consistent with
    other docs.


Well, I don't deeply care either (beyond bike-shed painting) - but there
is content to the TLV so it has length to be included in the calculation.

                 3) Sec 2.2 "The size of the label range is determined
        by the
                 number of Set
                         Identifiers (SI) (section 1 of
                 [I-D.ietf-bier-architecture]) that
                         are used in the network.  Each SI maps to a
        single label
                 in the
                         label range.  The first label is for SI=0, the
        second
                 label is for
                         SI=1, etc.:

                 This implies that there is no way to indicate only a
        label for
                 SI=1 or a
                 range for SI=1 to 3. That seems unfortunate and assumes
        that the
                 BFR-ids
                 are always allocated from SI=0 up.   Is there a reason
        not to
                 use some
                 of the reserved bits to indicate the starting SI value?


             I hope this has been clarified by Andrew and Tony already.


        Sure - I'm fine with what the WG wants here - and labels aren't too
        limited. My concern
        was about efficiency and future flexibility.


                 4) Sec 2.3: The Tree type is a 1 octet value - that doesn't
                 appear to
                 have any IANA allocation or meaning clearly indicated -
        beyond the
                 parenthetical that 0=SPF.  Please fix this.


             will add description for value 0. Will also add the need
        for new
             registry in "IANA Considerations" section.


        Cool - unless there's a reason, could it be a BIER-related
        registry that
        both the IS-IS work and OSPF work
        can refer to?


    right, that make sense. In such case, it should be defined outside
    of IGP BIER drafts, shouldn't it?


It's ok to have it here.  This is a BIER WG draft and it isn't needed
until this or the ISIS one.
Either can work.  It could be in the mpls-encap draft, but that's ready
for IETF Last Call and it isn't
used there - so it would need more explanation.

ok, I define it here.

Sounds good.  Thanks!

Alia


thanks,
Peter


                 5) Sec 2.5: This section could benefit greatly from a
        diagram -
                 showing
                 the advertising router for a prefix, the ABR, and what
        is then
                 flooded
                 for the BIER MPLS Sub-TLV for the new areas.


             can you please clarify what type of diagram do you have in
        mind?


        A fairly simple one :-) where there are 3 areas - with the
        middle being
        the backbone.
        Have a BFER in each area.  Describe what is advertised by each
        BFER and
        then by
        the ABR.

             I tend to agree with Andrew that we have similar section in
        many
             other documents and we've never included any diagram
        really. Anyway,
             I don't have a problem adding it if it helps.


        Frankly, the language/phrasing was such that I had to stop and think
        about it for 5 minutes or so to be
        confident that I understood and agreed with what was there.  That's
        generally my sign that added clarity
        could be useful - but it could just be me or a bad day.


    let me try.


Thanks,
Alia

    thanks,
    Peter





                 Minor:

                 4) Sec 2.3: "Label Range Base: A 3 octet field, where
        the 20
                 rightmost
                 bits represent the first label in the label range."
        What about
                 the top
                 4 bits?  Are they Must Be Zero (MBZ)?  How about making
        that
                 explicit?
                 Are they potential future flags?/


             top for bits are ignored. I'll spell that out explicitly.


        Sounds good.

        I look forward to getting these from the WG.  If I can put them into
        IETF Last Call by the end of the
        week, then we can have them on the Oct 26 telechat and hopefully
        approved before IETF 100.

        Regards,
        Alia

             thanks,
             Peter


                 Thanks,
                 Alia