Re: [Idr] 1 Week last call on changes to: draft-ietf-idr-bgp-ls-segment-routing-ext-17.txt [3/25/2021 to 4/1/2021]

["Les Ginsberg (ginsberg)" <[e-mail]>]

Ketan/Alvaro –

Looking at this again, I can see why some text is necessary.
Here is an alternate suggestion:

         IS-IS flags correspond to the IPv4/IPv6 Extended Reachability
         Attribute Flags defined in section 2.1 of [RFC7794].  In the case
         of the X-flag when associated with IPv6 prefix reachability the
         setting corresponds to the setting of the X-flag in the fixed format of
         IS-IS TLVs 236 [RFC5308] and 237 [RFC5120].

I believe this deserves to be more than a “Note” because RFC 7794 requires X-flag in Prefix Reachability sub-TLV in such cases to be sent as 0 and ignored on receipt – which means you cannot derive the X-flag from Prefix Attributes sub-TLV, but you still want to use the bit position of the X-flag in Prefix Attributes sub-TLV for the value derived from the IPv6 Prefix Reachability TLVs.

   Les



From: Ketan Talaulikar (ketant) <[e-mail]>
Sent: Tuesday, April 06, 2021 10:51 AM
To: Alvaro Retana <[e-mail]>; Susan Hares <[e-mail]>; Les Ginsberg (ginsberg) <[e-mail]>; [e-mail]
Cc: [e-mail]
Subject: RE: [Idr] 1 Week last call on changes to: draft-ietf-idr-bgp-ls-segment-routing-ext-17.txt [3/25/2021 to 4/1/2021]

Hi Alvaro/Les,

The RFC7794 covers the ISIS protocol handling of the X-flag from either the IPv4/IPv6 Extended Reachability Attribute Flags sub-TLV or from the fixed form TLVs 236 & 237.

The BGP-LS draft currently says that the contents of the BGP-LS Prefix Attribute Flags TLV is derived from the IPv4/IPv6 Extended Reachability Attribute Flags sub-TLV in case of ISIS. It does not cover this “special” handling that is required for the X-flag in TLV 236/237 and populating that info into BGP-LS. This is the clarification that I was referring to and I did not see that as a duplication.

I am OK in skipping this text update if you still believe it to be unnecessary.

Thanks,
Ketan


From: Alvaro Retana <[e-mail]<mailto:[e-mail]>>
Sent: 06 April 2021 23:07
To: Susan Hares <[e-mail]<mailto:[e-mail]>>; Les Ginsberg (ginsberg) <[e-mail]<mailto:[e-mail]>>; Ketan Talaulikar (ketant) <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
Cc: [e-mail]<mailto:[e-mail]>
Subject: Re: [Idr] 1 Week last call on changes to: draft-ietf-idr-bgp-ls-segment-routing-ext-17.txt [3/25/2021 to 4/1/2021]

Les:

Hi!

The text is not normative…but I do see your point about duplication.  I’m fine with not adding the note.

Thanks!

Alvaro.


On April 6, 2021 at 1:32:49 PM, Les Ginsberg (ginsberg) (ginsberg=[e-mail]<mailto:ginsberg=[e-mail]>) wrote:
Ketan –

I always prefer NOT to duplicate normative statements found in referenced documents as there are only two possibilities – neither of which is useful:

1)You will get it right – in which case the text will be redundant
2)You will get it wrong – in which case the text will introduce ambiguity

You have referenced RFC 7794 – I think that should be all that is required.
No change please.

   Les


From: Idr <[e-mail]<mailto:[e-mail]>> On Behalf Of Ketan Talaulikar (ketant)
Sent: Tuesday, April 06, 2021 9:09 AM
To: Susan Hares <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
Cc: [e-mail]<mailto:[e-mail]>
Subject: Re: [Idr] 1 Week last call on changes to: draft-ietf-idr-bgp-ls-segment-routing-ext-17.txt [3/25/2021 to 4/1/2021]


Hello All,



A minor point (IMHO worth clarification) related to this draft-ietf-idr-bgp-ls-segment-routing-ext has come to my notice out of the ongoing AD-review and discussion [1] for the draft-ietf-lsr-isis-srv6-extensions.



This is related to the Prefix Attribute Flags TLV : https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-ls-segment-routing-ext-17#section-2.3.2



Currently the draft says that for IS-IS they are derived from the IPv4/IPv6 Extended Reachability Attribute Flags sub-TLV as specified in https://datatracker.ietf.org/doc/html/rfc7794#section-2.1



What we missed (though it is described in RFC7794 sec 2.1), is that for the X-flag, the value needs to be picked from the IS-IS TLVs 236 and 237.



The proposed changes are in sec 2.3.2 as follows:



<OLD/>

      *  IS-IS flags correspond to the IPv4/IPv6 Extended Reachability

         Attribute Flags defined in section 2.1 of [RFC7794]<https://datatracker.ietf.org/doc/html/rfc7794#section-2.1>

</OLD>



<NEW/>

      *  IS-IS flags correspond to the IPv4/IPv6 Extended Reachability

         Attribute Flags defined in section 2.1 of [RFC7794]. Note: for

         the prefix reachability advertisement via IS-IS TLVs 236

         [RFC5308] and 237 [RFC5120], the value of the X-flag to be set

         in the BGP-LS TLV is determined from the fixed format of those

         IS-IS TLVs instead of the IS-IS IPv4/IPv6 Extended Reachability

         Attributes Flags sub-TLV.

</NEW>



I wanted to check with WG/chairs/AD if this is something that we ought to fix/update at this stage in the draft.



Thanks,

Ketan



[1] https://mailarchive.ietf.org/arch/msg/lsr/HAtgICjP4qB23LKfbyZQigDeQSo/





-----Original Message-----
From: Idr <[e-mail]<mailto:[e-mail]>> On Behalf Of Susan Hares
Sent: 25 March 2021 20:07
To: [e-mail]<mailto:[e-mail]>
Subject: [Idr] 1 Week last call on changes to: draft-ietf-idr-bgp-ls-segment-routing-ext-17.txt [3/25/2021 to 4/1/2021]



IDR:



This is a 1 Week WG call for comments the changes to draft-ietf-bgp-ls-segment-routing-ext-17.txt.



https://tools.ietf.org/html/draft-ietf-idr-bgp-ls-segment-routing-ext-17



The comments on this document are only for the changes from -16 to -17.txt



Ketan summarized the changes in his early message with



"This update to the BGP-LS SR draft (that was sitting in the RFC-editor Q due to misref) was required to the recent changes in the

https://datatracker.ietf.org/doc/html/draft-ietf-lsr-ospf-prefix-originator-

09 that was the missing reference as part of the AD review.



It updates the references to the Source Router Identifier TLV for OSPF and introduces a new TLV for the Source OSPF Router-ID TLV to cover the new TLV introduced by draft-ietf-lsr-ospf-prefix-originator."



It is a fine summary of the changes.



Please send comments if you are concerned about the changes.



Unless comments are heard, the intent is to allow the RFC editor to publish based on the -17.txt version.



Cheers, Susan Hares





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