Hi Peter, > From: Peter Psenak [mailto:[email protected]] > > Hi Bruno, > > On 12/05/2021 10:24, [email protected] wrote: > > Hi Peter, > > > > Thanks for the answer. > > Please see inline. > > > >> From: Peter Psenak [mailto:[email protected]] > >> > >> Hi Bruno, > >> > >> > >> On 12/05/2021 09:51, [email protected] wrote: > >>> Hi Xuesong, > >>> > >>> Clarification question: are you talking about interoperability (between > >>> two nodes) or compliancy (between an implementation and the RFC)? > >> > >> I'm afraid the two are related. If we mandate the Prefix Attribute > >> Sub-TLV inside the Locator TLV, we would have to say that the Locator > >> TLV without the Prefix Attribute Sub-TLV MUST be ignored. > > > > Mandating the advertisement is one thing (if it's useful, not to mention > required, let's advertise it). > > Then why would we have to say that the Locator TLV without the Prefix > Attribute Sub-TLV MUST be ignored ? On the receiver side, a priori, current > spec allows for both (presence & non-presence), no? That seem like an error > handling situation that we can choose. > > if we mandate something we need to say what happens when the mandated > data is not present
Absolutely. I could not agree more. I call this error handling. >- typically we ignore. OK, but here we seem free to define "whatever" error handling we want since current version of the draft allows for both presence or non-presence. Thanks, --Bruno > If we don't ignore, then we > are not really mandating it. > > thanks, > Peter > > > > > > Thanks for the discussion, > > --Bruno > > > >> As a result, > >> implementations that do not send the Prefix Attribute Sub-TLV would not > >> just be not compliant, but would also not interoperate with the ones > >> that follow the specification. > >> > >> thanks, > >> Peter > >> > >>> > >>> If the former, could you please spell out the interop issue? > >>> > >>> Thanks, > >>> > >>> Best regards, > >>> > >>> --Bruno > >>> > >>> *From:*Lsr [mailto:[email protected]] *On Behalf Of *Gengxuesong > >>> (Geng Xuesong) > >>> *Sent:* Wednesday, May 12, 2021 9:16 AM > >>> *To:* Les Ginsberg (ginsberg) <[email protected]>; Shraddha Hegde > >>> <[email protected]>; Alvaro Retana > >>> <[email protected]>; Peter Psenak (ppsenak) > >> <[email protected]>; > >>> [email protected] > >>> *Cc:* [email protected]; [email protected]; > >>> Van De Velde, Gunter (Nokia - BE/Antwerp) > >> <[email protected]> > >>> *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 Les, > >>> > >>> Prefix Attributes sub-TLV is necessary when locator is leaked. > >>> > >>> So we are not against Prefix Attribute sub-TLV implementation. We just > >>> propose to keep it optional (“should” rather than “must”) for > >>> interoperability. > >>> > >>> Best > >>> > >>> Xuesong > >>> > >>> *From:*Les Ginsberg (ginsberg) [mailto:[email protected]] > >>> *Sent:* Wednesday, May 12, 2021 6:29 AM > >>> *To:* Shraddha Hegde <[email protected] > >>> <mailto:[email protected]>>; Alvaro Retana > >>> <[email protected] <mailto:[email protected]>>; Peter > Psenak > >>> (ppsenak) <[email protected] <mailto:[email protected]>>; > >> [email protected] > >>> <mailto:[email protected]>; Gengxuesong (Geng Xuesong) > >>> <[email protected] <mailto:[email protected]>> > >>> *Cc:* [email protected] <mailto:[email protected]>; > >>> [email protected] > >>> <mailto:[email protected]>; Van De Velde, > >>> Gunter (Nokia - BE/Antwerp) <[email protected] > >>> <mailto:[email protected]>> > >>> *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 > >>> > >>> Shraddha/ Xuesong – > >>> > >>> Since Prefix Attributes sub-TLV is required for correct operation when a > >>> Locator is leaked, would it be safe to assume that your implementations > >>> either do not leak Locators or you advise your customers not to deploy > >>> this feature with multiple levels? > >>> > >>> The problem with allowing the sub-TLV to be optional is that if the > >>> sub-TLV is omitted you cannot tell whether the Locator has been leaked > – > >>> so you don’t know whether you have a problem or not. > >>> > >>> The safest thing to do is require prefix-attributes sub-TLV always – > >>> then you can guarantee that if the prefix is leaked the necessary > >>> information will be present. > >>> > >>> Anything else leaves us vulnerable. > >>> > >>> We all appreciate interoperability considerations, but frankly this is a > >>> gap that needs to be closed to support correct operation. > >>> > >>> Les > >>> > >>> *From:*Lsr <[email protected] <mailto:[email protected]>> *On > >>> Behalf Of *Shraddha Hegde > >>> *Sent:* Tuesday, May 11, 2021 8:21 AM > >>> *To:* Alvaro Retana <[email protected] > >>> <mailto:[email protected]>>; Peter Psenak (ppsenak) > >>> <[email protected] <mailto:[email protected]>>; [email protected] > >>> <mailto:[email protected]> > >>> *Cc:* [email protected] <mailto:[email protected]>; > >>> [email protected] > >>> <mailto:[email protected]>; Van De Velde, > >>> Gunter (Nokia - BE/Antwerp) <[email protected] > >>> <mailto:[email protected]>> > >>> *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 > >>> > >>> Juniper has an implementation of SRv6 that does not support Prefix > >>> attributes sub-tlv in locator TLV. > >>> > >>> We would prefer not to change the optional sub-TLV to MUST. > >>> > >>> Rgds > >>> > >>> Shraddha > >>> > >>> Juniper Business Use Only > >>> > >>> *From:*Lsr <[email protected] <mailto:[email protected]>> *On > >>> Behalf Of *Alvaro Retana > >>> *Sent:* Friday, May 7, 2021 7:23 PM > >>> *To:* Peter Psenak <[email protected] > <mailto:[email protected]>>; > >>> [email protected] <mailto:[email protected]> > >>> *Cc:* [email protected] <mailto:[email protected]>; > >>> [email protected] > >>> <mailto:[email protected]>; Van De Velde, > >>> Gunter (Nokia - BE/Antwerp) <[email protected] > >>> <mailto:[email protected]>> > >>> *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 > >>> > >>> *[External Email. Be cautious of content]* > >>> > >>> 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 ([email protected] > >>> <mailto:[email protected]>) 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/ > >>> > > >>> > >>> > >> > __________________________________________________________ > >> > __________________________________________________________ > >> _____ > >>> > >>> Ce message et ses pieces jointes peuvent contenir des informations > >> confidentielles ou privilegiees et ne doivent donc > >>> pas etre diffuses, exploites ou copies sans autorisation. Si vous avez > >>> recu > ce > >> message par erreur, veuillez le signaler > >>> a l'expediteur et le detruire ainsi que les pieces jointes. Les messages > >> electroniques etant susceptibles d'alteration, > >>> Orange decline toute responsabilite si ce message a ete altere, deforme > ou > >> falsifie. 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