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

[Huaimo Chen <[e-mail]>]

Hi Les,

    Thank you very much for your valuable comments and suggestions.
    My responses are inline below with [HC3].

Best Regards,
Huaimo
________________________________
From: Les Ginsberg (ginsberg) <[e-mail]>
Sent: Monday, August 8, 2022 1:02 PM
To: Huaimo Chen <[e-mail]>; Les Ginsberg (ginsberg) <ginsberg=[e-mail]>; [e-mail] <[e-mail]>
Subject: RE: [Bier] I-D Action: draft-ietf-bier-te-isis-01.txt


Huaimo –



In order to support a variable length bit field, you will need to change the format of the sub-TLV. So, while you may not need to support more larger scale today, you do not want to standardize a format that will have to be changed.

I think you need to revise the format now. And if you are advertising a bit string, this could become quite large. RFC 8296 defines support for up to 4K bits – which would require 512 bytes – not feasible in IS-IS in a 255 byte TLV.

I suggest you advertise this as a 0-based bit number. This means that a 16 bit field (2 octets) is sufficient to cover Bits 0-65535.

[HC3]: The BitPosition field of 16 bits (2 octets) is to store a Bit Position (or Bit Number) assigned to a link. The maximum Bit Position (or Bit Number) is the maximum number of links in a network if one Bit Position is assigned to two ends of a link. For a very large network, its total number of links may be greater than 65535. The BitPosition field of 3 octets in maximum is enough.



I also question why you need to include the DisEndBitPosition. For this to be correct, it needs to match the value locally assigned on the DIS – which means it is safer to retrieve the value from the corresponding advertisement by the DIS itself.

Otherwise, the non-DIS nodes would have to update their advertisements whenever they see a change in what is advertised by the DIS. This is not desirable.

[HC3]: I will remove this field accordingly.



So the sub-TLV format becomes:



Type:  1 octet

Length:  1 octet

sub-domain-id:  1 octet

BAR:  1 octet

IPA:  1 octet

BitNumber :  2-octets Specifies the local bit position (0 based) assigned to this link/neighbor

[HC3]: BitNumber field is extended as follows:

the first bit (from left to right) is used as a flag named E flag. When E = 0, the BitNumber field is 2 octets (i.e., 16 bits), the last 15 bits stores a Bit Position. When E = 1, the BitNumber field is 3 octets (i.e., 24 bits), the last 23 bits stores a Bit Position.





   Les



From: BIER <[e-mail]> On Behalf Of Huaimo Chen
Sent: Monday, August 8, 2022 8:04 AM
To: Les Ginsberg (ginsberg) <[e-mail]>; Les Ginsberg (ginsberg) <ginsberg=[e-mail]>; [e-mail]
Subject: Re: [Bier] I-D Action: draft-ietf-bier-te-isis-01.txt



Hi Les,



    Thanks much for your question.

    My answer is inline below with [HC2].



Best Regards,

Huaimo

________________________________

From: Les Ginsberg (ginsberg) <[e-mail]<mailto:[e-mail]>>
Sent: Wednesday, August 3, 2022 9:58 AM
To: Huaimo Chen <[e-mail]<mailto:[e-mail]>>; Les Ginsberg (ginsberg) <ginsberg=[e-mail]<mailto:ginsberg=[e-mail]>>; [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>
Subject: RE: [Bier] I-D Action: draft-ietf-bier-te-isis-01.txt



Huaimo -

Thanx for addressing my comments so quickly.

Changes look fine - but I do have one question.

You eliminated the text:

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

Does this mean you have no need to ever support more than 16 bits in these fields??

[HC2]: It should be ok for now. For scalability, there is a need for supporting more than 16 bits in these fields.

   Les

> -----Original Message-----
> From: BIER <[e-mail]<mailto:[e-mail]>> On Behalf Of Huaimo Chen
> Sent: Tuesday, August 2, 2022 7:59 PM
> To: Les Ginsberg (ginsberg) <ginsberg=[e-mail]<mailto:ginsberg=[e-mail]>>;
> [e-mail]<mailto:[e-mail]>
> Subject: Re: [Bier] I-D Action: draft-ietf-bier-te-isis-01.txt
>
> Hi Les,
>
>     Thank you very much for your valuable comments.
>     I have addressed them in the updated draft (uploaded).
>     My responses are also inline below with [HC].
>
> Best Regards,
> Huaimo
> -----Original Message-----
> From: BIER <[e-mail]<mailto:[e-mail]>> On Behalf Of Les Ginsberg (ginsberg)
> Sent: Friday, July 29, 2022 4:59 PM
> To: [e-mail]<mailto:[e-mail]>
> Subject: Re: [Bier] I-D Action: draft-ietf-bier-te-isis-01.txt
>
> Some pedantic comments on this draft:
>
> For the new BIER-TE sub-TLV:
>
> 1)The relevant registry has been renamed to be "IS-IS Sub-TLVs for TLVs
> Advertising Neighbor Information". Please use this new name.
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fww
> w.iana.org%2Fassignments%2Fisis-tlv-codepoints%2Fisis-tlv-
> codepoints.xhtml%23isis-tlv-codepoints-advertising-neighbor-
> information&amp;data=05%7C01%7Chuaimo.chen%40futurewei.com%7C5b
> bd38c256024261ea5608da71a546c0%7C0fee8ff2a3b240189c753a1d5591fedc%
> 7C1%7C0%7C637947251926210034%7CUnknown%7CTWFpbGZsb3d8eyJWIjoi
> MC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C300
> 0%7C%7C%7C&amp;sdata=ybC6zOJkG1sRe%2FQosV23MElysXHkg7jnHS70N
> %2Bf7bpE%3D&amp;reserved=0
> [HC]: I have renamed it as you suggested.
>
> 2)Please do NOT insert padding to keep content aligned on a 4 byte
> boundary. This may be useful for OSPF, but it is not for IS-IS as TLVs are NOT
> aligned inside an LSP. All you are doing is wasting space - which is precious in
> IS-IS given the limited LSP space.
> [HC]: Removed padding.
>
> 3)You say in Section 2:
>
> "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 see how the receiver of the sub-TLV could tell whether the 2 octet or
> 4 octet encoding was sent as you have nothing that specifies the length of
> these fields.
> You can't use the total length of the sub-TLV as it could include optional sub-
> sub-TLVs.
>
> ??
> [HC]: Deleted the quoted text.
>
> 4)In IANA section, I do not know why you specified "N" for TLVs 23 and 223.
> While RFC 5311 (which defines these TLVs) is not popular, if there was an
> implementation, I see no reason why it should be invalid to send the BIER-TE
> info in these TLVs.
> [HC]: Changed "n" to "y" for TLVs 23 and 223.
>
> Thanx.
>
>     Les
>
>
> > -----Original Message-----
> > From: BIER <[e-mail]<mailto:[e-mail]>> On Behalf Of [e-mail]<mailto:[e-mail]>
> > Sent: Friday, July 29, 2022 12:13 PM
> > To: [e-mail]<mailto:[e-mail]>
> > Cc: [e-mail]<mailto:[e-mail]>
> > Subject: [Bier] I-D Action: draft-ietf-bier-te-isis-01.txt
> >
> >
> > 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%2Fdata
> tracker.ietf.org%2Fdoc%2Fdraft-ietf-bier-te-
> isis%2F&amp;data=05%7C01%7Chuaimo.chen%40futurewei.com%7C5bbd38
> c256024261ea5608da71a546c0%7C0fee8ff2a3b240189c753a1d5591fedc%7C1
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> 4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%
> 7C%7C%7C&amp;sdata=99ojCa2m%2BTeMk0OfxeifsmVrhvNaK7jQJp0fu0syR
> N8%3D&amp;reserved=0
> >
> > There is also an htmlized version available at:
> >
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdata
> tracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-ietf-bier-te-isis-
> 01&amp;data=05%7C01%7Chuaimo.chen%40futurewei.com%7C5bbd38c256
> 024261ea5608da71a546c0%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0
> %7C637947251926210034%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjA
> wMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C
> %7C&amp;sdata=%2F8qaH0ZvQBAfGM4WIre0jpcI6As7wjXjdqbxOfdGHxo%3
> D&amp;reserved=0
> >
> > A diff from the previous version is available at:
> >
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fww
> w.ietf.org%2Frfcdiff%3Furl2%3Ddraft-ietf-bier-te-isis-
> 01&amp;data=05%7C01%7Chuaimo.chen%40futurewei.com%7C5bbd38c256
> 024261ea5608da71a546c0%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0
> %7C637947251926210034%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjA
> wMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C
> %7C&amp;sdata=L77o0dGWGuSwL9vSm1Durc56Fl5zONoDq%2F8ij12v9lc%3D
> &amp;reserved=0
> >
> >
> > Internet-Drafts are also available by rsync at rsync.ietf.org::internet-drafts
> >
> >
> > _______________________________________________
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