Re: [Bier] I-D Action: draft-ietf-bier-te-isis-01.txt

[Huaimo Chen <[e-mail]>]

Hi Toerless,

    Thanks much for your comments.
    My responses are inline below with [HC].

Best Regards,
Huaimo
________________________________
From: BIER <[e-mail]> on behalf of Toerless Eckert <[e-mail]>
Sent: Friday, August 12, 2022 11:52 AM
To: [e-mail] <[e-mail]>
Subject: Re: [Bier] I-D Action: draft-ietf-bier-te-isis-01.txt

A)

> No Sub-Sub-TLV is defined so far.

are ?
[HC]: No Sub-Sub-TLV is defined so far.

B)

> Note that if each of BitPosition and DrEndBitPosition uses more
> than 2 octets, we use 4 or more octets for each of them.

I do not understand what this means. Are you implying that the field
BitPosition in your Sub-TLV could be longer than the indicated 16 bit
in Figure 1 ? If so, how would a recipient know that it is not 16 bit long ?
[HC]:  The BitPosition assigned to (or configured for) an adjacency of
the network topology is distributed in the Sub-TLV.
If the number of adjacencies is greater than 64k in the network,
it cannot be represented by 16 bits directly.

I also don't think the BIER/BIER-TE architecture would permit this
field to be longer than 16 bits, we (BIER/BIER-TE) only support 64k in both.
[HC]: If BIER-TE architecture does not permit this and only supports 64k
adjacencies, then the distribution of the bit positions for the adjacencies
in this draft will follow it.

C) I think the word BitPosition and DrEndBitPosition are not correct.

What you do seemingly want to encode is what BIER (and RFC8401) calls BFR-id,
and BIER-TE unfortunately weaseled out giving a new name (unfortunately,
bfr-id does not make sense for BIER-TE even though the values themselves
do make equally sense). I guess we should have given it a name like ADJ-id,
and that is what i would suggest calling this field. Maybe add simple
explanation:

   ADJ-id = BitPosition + SI * BSL (like BFR-id in BIER)

Or else, we can also just call it bfr-id like RFC8401, just noting that
the semantic of the indicated bit is not that of a BIER bfr-id, but of
a BIER-TE foward_connected() adjacency.

In any case, bit position / BitPosition is consistently used in rfc8279 and
BIER-TE to solely refer to bits within a BitString in a packet (<= 4096), not
across all the BitString bits spossible for an SD (<= 64k).
[HC]: This draft just distributes the bit position configured for or assigned to
an adjacency.

D) I still don't think i have seen an answer giving an exxample of what
DrEndBitPosition could be. Still curious.
[HC]: Draft "BIER-TE for Broadcast Link" describes it in detail.

Cheers
    Toerless


On Fri, Jul 29, 2022 at 12:13:19PM -0700, [e-mail] wrote:
>
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the Bit Indexed Explicit Replication WG of the IETF.
>
>         Title           : IS-IS Extensions for BIER-TE
>         Authors         : Huaimo Chen
>                           Mike McBride
>                           Aijun Wang
>                           Gyan S. Mishra
>                           Yanhe Fan
>                           Lei Liu
>                           Xufeng Liu
>   Filename        : draft-ietf-bier-te-isis-01.txt
>   Pages           : 7
>   Date            : 2022-07-29
>
> Abstract:
>    This document describes IS-IS extensions for distributing
>    BitPositions configured on the links in "Bit Index Explicit
>    Replication Traffic Engineering" (BIER-TE) domain.
>
>
>
> The IETF datatracker status page for this draft is:
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-ietf-bier-te-isis%2F&amp;data=05%7C01%7Chuaimo.chen%40futurewei.com%7C18da4fa2fc66453333b908da7c7abbf4%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637959163847747562%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=VcsW5ozVjbFNZIo%2BBxHJPzAuMlM1puXxE0NsRBfA7CI%3D&amp;reserved=0
>
> There is also an htmlized version available at:
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-ietf-bier-te-isis-01&amp;data=05%7C01%7Chuaimo.chen%40futurewei.com%7C18da4fa2fc66453333b908da7c7abbf4%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637959163847747562%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=TSJ%2BADJv2yT6tcL7UKuCi%2F8t0%2BMYfP%2Fpm7R28KnPHek%3D&amp;reserved=0
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> A diff from the previous version is available at:
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ietf.org%2Frfcdiff%3Furl2%3Ddraft-ietf-bier-te-isis-01&amp;data=05%7C01%7Chuaimo.chen%40futurewei.com%7C18da4fa2fc66453333b908da7c7abbf4%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637959163847747562%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=HtA2iK%2FdNH551QWCSRfkalgkFnGBgxDbCRkV8wb02Nk%3D&amp;reserved=0
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>
> Internet-Drafts are also available by rsync at rsync.ietf.org::internet-drafts
>

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