+1
Cheers, Jeff On May 7, 2021, 9:53 AM -0700, Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org>, wrote: > As has been mentioned in this thread, the need for the prefix-attributes > sub-TLV to correctly process leaked advertisements is not unique to the > Locator TLV. The reason prefix-attributes TLV was created was to address the > same gap with IP/IPv6 reachability advertisements. > And I think by now implementations (certainly ones that support newer > functionality like SRv6) should have added support for prefix-attributes > sub-TLV . > > In the case of the Locator TLV – since this is new functionality – we have > the option of mandating prefix-attributes sub-TLV – something we could not do > with IP/IPv6 Reachability since that has been deployed for many years. > > But, please recognize two consequences of the MUST option: > > 1)Implementations may have to deal w backwards compatibility w early > deployments of SRv6. This would only be an issue if there are implementations > that currently do NOT send prefix-attributes sub-TLV w Locator TLV. > Are there any such implementations?? > > 2)In the case where the deployment is a single level, it could be argued that > prefix-attributes sub-TLV isn’t needed. > I personally would NOT make such an argument, but we should understand that > MUST applies to this case as well. > > If everyone is OK with these consequences (personally I am OK) then I think > it is fine to go with MUST. > > Les > > > From: Lsr <lsr-boun...@ietf.org> On Behalf Of Ketan Talaulikar (ketant) > Sent: Friday, May 07, 2021 7:00 AM > To: Alvaro Retana <aretana.i...@gmail.com>; Peter Psenak (ppsenak) > <ppse...@cisco.com>; lsr@ietf.org > Cc: cho...@chopps.org; draft-ietf-lsr-isis-srv6-extensi...@ietf.org; Van De > Velde, Gunter (Nokia - BE/Antwerp) <gunter.van_de_ve...@nokia.com> > Subject: Re: [Lsr] Last Call: <draft-ietf-lsr-isis-srv6-extensions-14.txt> > (IS-IS Extension to Support Segment Routing over IPv6 Dataplane) to Proposed > Standard > > Hi Peter, > > I agree that the support for the Prefix Attribute Flags TLV is required in > the Locator TLV. > > Thanks, > Ketan > > From: Lsr <lsr-boun...@ietf.org> On Behalf Of Alvaro Retana > Sent: 07 May 2021 19:23 > To: Peter Psenak (ppsenak) <ppse...@cisco.com>; lsr@ietf.org > Cc: cho...@chopps.org; draft-ietf-lsr-isis-srv6-extensi...@ietf.org; Van De > Velde, Gunter (Nokia - BE/Antwerp) <gunter.van_de_ve...@nokia.com> > Subject: Re: [Lsr] Last Call: <draft-ietf-lsr-isis-srv6-extensions-14.txt> > (IS-IS Extension to Support Segment Routing over IPv6 Dataplane) to Proposed > Standard > > On May 3, 2021 at 5:17:58 AM, Peter Psenak wrote: > > > Technically I agree with you and if everybody agrees, I'm fine to > > enforce the presence of the Prefix Attribute Flags TLV in the Locator TLV. > > So...what does everyone else think? > > We need to close on this point before the IESG evaluates the document. I'm > requesting it to be put on the May/20 telechat, which means that we should > have a resolution and updated draft by the end of next week. > > > Thanks! > > Alvaro. > > > On May 3, 2021 at 5:17:58 AM, Peter Psenak (ppse...@cisco.com) wrote: > > Hi Gunter, > > > > Prefix Attribute Flags Sub-TLV has been defined as an optional Sub-TLV. > > The problem you describe is not specific to Locator TLV, same applies to > > regular IPv4/v6 prefixes (forget SR MPLS for a while) - if the Prefix > > Attribute Flags TLV is not included, one can not tell whether the prefix > > has been propagated (L1->L2) or generated as a result of the local > > interface attached on the originator. Same applies to redistribution and > > R-flag for IPv4 prefix TLVs. > > > > SRv6 Locator TLV has been defined a while back and the Prefix Attribute > > Flags Sub-TLV has always been an optional Sub-TLV of it. I'm not sure we > > can start to mandate the Prefix Attribute Flags TLV at this point. > > > > Technically I agree with you and if everybody agrees, I'm fine to > > enforce the presence of the Prefix Attribute Flags TLV in the Locator TLV. > > > > thanks, > > Peter > > > > > > On 03/05/2021 10:45, Van De Velde, Gunter (Nokia - BE/Antwerp) wrote: > > > Hi Peter, All, > > > > > > Could we update to "draft-ietf-lsr-isis-srv6-extensions" that the > > > prefix-attribute tlv is mandatory when a locator is redistributed? > > > > > > Why? > > > *When calculating a LFA for an SRv6 End.SID we better know if the locator > > > has been redistributed or not for a correct operation. > > > > > > Reasoning: > > > * A locator has the D bit. This one is set when we redistribute from L2 > > > to L1. > > > ** So this end-sid will not be used as we know that it is redistributed. > > > > > > * In the other direction (L1-L2), we only know that a locator is > > > redistributed from L1 to L2 if the prefix-attribute sub-tlv is advertised. > > > ** This means if the operator does not configure advertisement of the > > > prefix-attribute tlv, ISIS could potentially use an end-sid which does > > > not terminate on the expected node. > > > > > > * Compared to sr-mpls, a prefix-sid has the R flag indicating it is > > > redistributed. > > > * We don't have that for locator end-sids. > > > > > > Relevant snip from " draft-ietf-lsr-isis-srv6-extensions" > > > > > > 7.1. SRv6 Locator TLV Format > > > > > > The SRv6 Locator TLV has the following format: > > > > > > 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 |R|R|R|R| MT ID | > > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > > > > Type: 27 > > > > > > Length: variable. > > > > > > R bits: reserved for future use. They MUST be > > > set to zero on transmission and MUST be ignored on receipt. > > > > > > MT ID: Multitopology Identifier as defined in [RFC5120]. > > > Note that the value 0 is legal. > > > > > > Followed by one or more locator entries of the form: > > > > > > 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 > > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > | Metric | > > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > | Flags | Algorithm | > > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > | Loc Size | Locator (variable)... > > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > | Sub-TLV-len | Sub-TLVs (variable) . . . | > > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > > > > > > > Metric: 4 octets. As described in [RFC5305]. > > > > > > Flags: 1 octet. The following flags are defined > > > > > > 0 > > > 0 1 2 3 4 5 6 7 > > > +-+-+-+-+-+-+-+-+ > > > |D| Reserved | > > > +-+-+-+-+-+-+-+-+ > > > > > > where: > > > D-flag: Same as described in section 4.1. of [RFC5305]. > > > > > > > > > G/ > > > > _______________________________________________ > Lsr mailing list > Lsr@ietf.org > https://www.ietf.org/mailman/listinfo/lsr
_______________________________________________ Lsr mailing list Lsr@ietf.org https://www.ietf.org/mailman/listinfo/lsr
