Re: [Gen-art] [Bier] Genart last call review of draft-ietf-bier-tether-04

Thank you Jeffrey.  On the major item, the proposed text addresses my 
concern.

On the minor issue, thank you.  I had failed to put the pieces together 
in my head, and you are correct.  Bier operation will take care of the 
problem and there is nothing to specify here. (In fact, that is the 
point.  It just works.)

Yours,

Joel

On 2/15/2024 11:04 PM, Jeffrey (Zhaohui) Zhang wrote:
> Hi Joel,
>
> Thanks for your review and comments.
> Please see zzh> below.
>
>
> Juniper Business Use Only
> -----Original Message-----
> From: BIER <bier-bounces@ietf.org> On Behalf Of Joel Halpern via Datatracker
> Sent: Thursday, February 15, 2024 6:10 PM
> To: gen-art@ietf.org
> Cc: bier@ietf.org; draft-ietf-bier-tether.all@ietf.org; last-call@ietf.org
> Subject: [Bier] Genart last call review of draft-ietf-bier-tether-04
>
> [External Email. Be cautious of content]
>
>
> Reviewer: Joel Halpern
> Review result: Ready with Issues
>
> I am the assigned Gen-ART reviewer for this draft. The General Area Review Team (Gen-ART) reviews all IETF documents being processed by the IESG for the IETF Chair.  Please treat these comments just like any other last call comments.
>
> For more information, please see the FAQ at
>
> <https://urldefense.com/v3/__https://wiki.ietf.org/en/group/gen/GenArtFAQ__;!!NEt6yMaO-gk!HnoMr9CvW2ImbH6LVeQkh-4CIMEuSojS_TOKsafTWXlzUP7cmGEeUOIn5afkDw9ceS4tFN9KrmjCnaQ$ >.
>
> Document: draft-ietf-bier-tether-04
> Reviewer: Joel Halpern
> Review Date: 2024-02-15
> IETF LC End Date: 2024-02-29
> IESG Telechat date: Not scheduled for a telechat
>
> Summary: This document is almost ready for publication as a proposed standard
>
> Major issues:
>      Section 3.1 on IGP Signaling states "The helper node (BFRx) MUST advertise
>      one or more BIER Helped Node sub-sub-TLVs".  However, I only find a vague
>      outline of this sub-sub TLV.  The code point for it is requested in the
>      IANA considerations section, but the description is a single sentence
>      easily misread and lacking the conventional diagrams and precision that is
>      used to define routing TLVs (and sub or sub-sub TLVs.)
>
> zzh> Point taken. How about the following?
>
>     Suppose that the BIER domain uses BIER signaling extensions to ISIS
>     [RFC8401] or OSPF [RFC8444].  The helper node (BFRx) MUST advertise
>     one or more BIER Helped Node sub-sub-TLVs in the BIER Info sub-TLV in
>     the case of ISIS or BIER Helped Node sub-TLVs in the BIER sub-TLV in
>     the case of OSPF, one for each helped node:
>
>          0                   1                   2                   3
>          0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
>         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>         |    Type       |   Length      |    Priority   |   Reserved    |
>         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>         |              Address of the Helped Node                       |
>         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>     The Type is TBD1 (in the case of ISIS) or TBD2 (in the case of OSPF).
>     The Value field starts with a one-octet Priority field, followed by a
>     one-octet Reserved field, and then the Address of the Helped Node
>     (X).  The Length is 6 for IPv4 and 18 for IPv6 respectively.
>
>
> Minor issues:
>      In the paragraph about multiple helpers helping a single non-supporting
>      router, I think I missed how one case works properly.  (Section 2,
>      additional considerations, paragraph 6).  The text says that the sending
>      BFR (BFR1 can choose to use multiple helpers if they are available.
>      Assuming that BFR1 chooses to use BFR2 and BFR 3 to reach BFRs 4 .. BFR N,
>      the text is clear that this results in BFR2 and BFR 3 both sending copies
>      of the packet to Router X.  That is fine.  It is load, but it is a
>      tradeoff.  However, it appears that both BFR2 and BFR 3 would send packets
>      to BFR4, and to all the other BFR children of X.  This results in duplicate
>      packets in the rest of the tree.  Is there some assumption I missed that
>      prevents this?
>
> Zzh> The BIER forwarding algorithm ensures that the two copies of the same packet that a BFR sends out never have overlapping bits in the BitString. Therefore, no duplication will happen.
> Zzh> Thanks!
> Zzh> Jeffrey
>
> Nits/editorial comments:
>
>
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