Just for the record, I’m ok with the latest text. Thanks!
Alvaro. On May 26, 2020 at 10:25:38 AM, Peter Psenak (ppse...@cisco.com) wrote: Hi Acee, updated the text based on your comments. thanks, Peter On 26/05/2020 16:07, Acee Lindem (acee) wrote: > Hi Peter, > > This is in response to the previous Email on your suggested text. > > On 5/26/20, 4:26 AM, "Peter Psenak" <ppse...@cisco.com> wrote: > > Hi Alvaro, > > please see inline (##PP) > > On 22/05/2020 16:59, Alvaro Retana 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.] > > ##PP > done. > > > > > > > > > > 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. > > ##PP > correct. It is always a new LSA that ABR needs to generate. Here it's > actually two LSAs. > > > > > 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. > > Here's my suggestion for OSPFv2 ABR related text: > > "The ELC signaling MUST be preserved when an OSPF Area Border Router > (ABR) distributes information between connected areas. To do so, ABR > MUST originate an OSPFv2 Extended Prefix Opaque LSA [RFC7684] including > the received ELC setting." > > Ok - I change "connected areas" to "areas" and "ABR MUST" to "an ABR MUST". > > Here's my suggested text for OSPFv2 ASBR case: > > "When an OSPF Autonomous System Boundary Router (ASBR) redistributes a > prefix from another instance of OSPF or from some other protocol, it > SHOULD preserve the ELC signaling for the prefix if it exists. To do so, > ASBR SHOULD originate Extended Prefix Opaque LSA [RFC7684] including the > ELC setting of the redistributed prefix. The flooding scope of the > Extended Prefix Opaque LSA MUST match the flooding scope of the LSA that > ASBR originates as a result of the redistribution. The exact mechanism > used to exchange ELC between protocol instances on the ASBR is outside > of the scope of this document." > > Sure - replace "ASBR SHOULD" with "an ASBR SHOULD", "that ASBR" with "that an ASBR", and "the ASBR is" with "an ASBR is" to be consistent. > Also, "originate Extended" with "originate an Extended". > > > > > > > > > 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. > > Here's my suggestion for OSPFv3 ABR and ASBR: > > "The ELC signaling MUST be preserved when an OSPFv3 Area Border Router > (ABR) distributes information between connected areas. The setting of > the ELC Flag in the Inter-Area-Prefix-LSA [RFC5340] or in the > Inter-Area-Prefix TLV [RFC8362], generated by ABR, MUST be the same as > the value the ELC Flag associated with the prefix in the source area." > > Same change - replace "connected areas" with "areas" and "by ABR" with "by an ABR". > > "When an OSPFv3 Autonomous System Boundary Router (ASBR) redistributes a > prefix from another instance of OSPFv3 or from some other protocol, it > SHOULD preserve the ELC signaling for the prefix if it exists. The > setting of the ELC Flag in the AS-External-LSA [RFC5340] or in the > External-Prefix TLV [RFC8362], generated by ASBR, MUST be the same as > the value the ELC Flag associated with the prefix in the source domain. > The exact mechanism used to exchange ELC between protocol instances on > the ASBR is outside of the scope of this document. > > Add "NSSA-LSA" as a case. Replace "by ASBR" with "by an ASBR" and "value the ELC" with "value of the ELC". > > Thanks, > Acee > > thanks, > Peter > > > > > > > > > > > >>> (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. > > > > > > > >
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