Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-isis-mpls-elc-12: (with DISCUSS and COMMENT)
Peter Psenak <ppsenak@cisco.com> Tue, 26 May 2020 12:22 UTC
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To: "Acee Lindem (acee)" <acee@cisco.com>, Alvaro Retana <aretana.ietf@gmail.com>, Benjamin Kaduk <kaduk@mit.edu>
Cc: "draft-ietf-isis-mpls-elc@ietf.org" <draft-ietf-isis-mpls-elc@ietf.org>, The IESG <iesg@ietf.org>, "lsr-chairs@ietf.org" <lsr-chairs@ietf.org>, "lsr@ietf.org" <lsr@ietf.org>
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From: Peter Psenak <ppsenak@cisco.com>
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Date: Tue, 26 May 2020 14:22:26 +0200
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Subject: Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-isis-mpls-elc-12: (with DISCUSS and COMMENT)
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Hi Acee, have you looked at the texts that I suggested in my response to Alvaro earlier today? Please see inline: On 26/05/2020 13:49, Acee Lindem (acee) wrote: > Hi Alvaro, > > See inline. > > On 5/22/20, 10:59 AM, "Alvaro Retana" <aretana.ietf@gmail.com> wrote: > > On May 21, 2020 at 3:39:03 PM, Benjamin Kaduk wrote: > > > Peter: > > Hi! > > > > With respect to Alvaro's clarification, your answer for (1) makes sense; > > thanks! I think Alvaro has offered to help work out what (if any) > > additional text we might want to be sure that the answer to (2) is clear in > > the document. > > I think that #1 is where some clarification could be useful. :-) > > > I'm including both ISIS and OSPF suggestions below to consolidate the > discussion. > > > ... > > > My interpretation of Ben's question is two-fold: > > > > > > (1) Would ISIS routers normally propagate the information to a > > > different level? The ELC is a new prefix attribute flag -- are prefix > > > attributes always propagated (unchanged) to other levels? If so, then > > > the requirement (MUST) is not needed. My reading of rfc7794 is that > > > the propagation is optional... > > > > depends on the attribute or a bit. Some are propagated some are not. > > That's why we are saying this one MUST be preserved. > > Right. > > For ISIS I think the current text is in line with the specification of > the other bits in rfc7794. No changes are needed. > > If anything, you may want to change the order of this sentence to > address Ben's comment: > > OLD> > When a router propagates a prefix between ISIS levels ([RFC5302], it > MUST preserve the ELC signaling for this prefix. > > NEW> > The ELC signaling MUST be preserved when a router propagates a prefix > between ISIS levels ([RFC5302]). > > [Similar for OSPF.] > > > > I think that for OSPF it is not that simple... > > For OSPFv2: rfc7684 says that the "scope of the OSPFv2 Extended Prefix > Opaque LSA depends on the scope of the advertised prefixes", which I > assume means that for intra-area prefixes the scope will be > area-local...so the ABR wouldn't simply propagate it; it would have to > originate a new LSA. > > I agree with the changes but have suggested alternate text. > > Suggestion (Add to 3.1)> > When an OSPFv2 Area Border Router (ABR) distributes information between > connected areas it SHOULD originate an OSPFv2 Extended Prefix Opaque LSA > [RFC7684] including the received ELC setting. If the received information > is included in an LSA with an AS-wide scope, then the new LSA is not needed. when would ABR do inter area propagation of what is advertised in AS scope LSA? I can not think of such a case. thanks, Peter > > I'd suggest: > > When an OSPFv2 Area Border Router (ABR) advertises prefix information between > areas and ELC information is was advertised for the prefix in the source area, the > ABR SHOULD originate an OSPFv2 Extended Prefix Opaque LSA [RFC7684] propagating > the prefix's source area setting. If the ELC setting, is also advertised in an OSPFv2 > Extended Prefix Opaque LSA with AS-wide scope, the additional LSA origination > Is not needed. > > > For OSPFv3: The PrefixOptions are *in* the LSA, but I couldn't find > anything in rfc5340 saying that the received values should be copied > into the Inter-Area-Prefix-LSA (nor that they should not). > > Suggestion (Add to 3.2)> > When an OSPFv3 Area Border Router (ABR) distributes information between > connected areas, the setting of the ELC Flag in the Inter-Area-Prefix-LSA > MUST be the same as the received value. > > I'd suggest: > > When an OSPFv3 Area Border Router (ABR) advertises information between > areas, the setting of the ELC flag in the Inter-area-prefix-LSA MUST be the > propagated unchanged. > > Thanks, > Acee > > > > > > > (2) If the propagation is not automatic, and the L1L2 router doesn't > > > support this specification, then what are the drawbacks/failure > > > scenarios? IOW, for multi-level operation is it a requirement that > > > the L1L2 support this specification? > > > > drawback are identical to what is mentioned in the Security > > Considerations section. > > I think that text is ok. > > > Thanks! > > Alvaro. > > >
- [Lsr] Benjamin Kaduk's Discuss on draft-ietf-isis… Benjamin Kaduk via Datatracker
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Alvaro Retana
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Alvaro Retana
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Acee Lindem (acee)
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Acee Lindem (acee)
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Acee Lindem (acee)
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Acee Lindem (acee)
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Alvaro Retana
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk