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

Toerless Eckert <> Fri, 12 August 2022 15:52 UTC

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From: Toerless Eckert <>
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Subject: Re: [Bier] I-D Action: draft-ietf-bier-te-isis-01.txt
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> No Sub-Sub-TLV is defined so far.

are ?


> 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 ?

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.

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

   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).

D) I still don't think i have seen an answer giving an exxample of what
DrEndBitPosition could be. Still curious.


On Fri, Jul 29, 2022 at 12:13:19PM -0700, 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:
> There is also an htmlized version available at:
> A diff from the previous version is available at:
> Internet-Drafts are also available by rsync at