Hi Peter, Ketan, We’ll do another WG last call on the updated IP Flex Algo document and it will update RFC 8362. As you probably surmised, this is useful for OSPFv3 IP Flex Algorithm when you want don’t want to use the prefix with the base algorithm.
From: Lsr <lsr-boun...@ietf.org> on behalf of Ketan Talaulikar <ketant.i...@gmail.com> Date: Thursday, October 6, 2022 at 3:35 AM To: Peter Psenak <ppsenak=40cisco....@dmarc.ietf.org> Cc: "lsr@ietf.org" <lsr@ietf.org> Subject: Re: [Lsr] RFC 8362 and LSInfinity Hi Peter, I support this "update" - not sure if it qualifies as a "clarification". Also, this obviously is doable only when the network has migrated to use only Extended LSAs (i.e., legacy LSAs are removed) as indicated in https://www.rfc-editor.org/rfc/rfc8362.html#section-6.1 In sparse-mode, the legacy LSAs are used. So if you want a prefix to be unreachable with the base algorithm, simply omit it from the legacy Intra-Area-Prefix LSA. Thanks, Acee Thanks, Ketan On Wed, Oct 5, 2022 at 3:01 PM Peter Psenak <ppsenak=40cisco....@dmarc.ietf.org<mailto:40cisco....@dmarc.ietf.org>> wrote: Hi Folks, metric of LSInfinity (0xFFFFFF) has been defined in RFC2328: LSInfinity The metric value indicating that the destination described by an LSA is unreachable. Used in summary-LSAs and AS-external-LSAs as an alternative to premature aging (see Section 14.1). It is defined to be the 24-bit binary value of all ones: 0xffffff. RFC5340 inherited it from RFC2328: Appendix B. Architectural Constants Architectural constants for the OSPF protocol are defined in Appendix B of [OSPFV2]. The only difference for OSPF for IPv6 is that DefaultDestination is encoded as a prefix with length 0 (see Appendix A.4.1). Both RFC2328 and RFC5340 used 16 bits metric for intra-area prefix reachability, so the LSInfinity was not applicable for intra-area prefixes. RFC8362 defines 24-bit metric for all prefix reachability TLVs - Intra-Area-Prefix TLV, Inter-Area-Prefix TLV, External-Prefix TLV. Although it is silent about the LSInfinity as such, it is assumed that such metric means unreachability for Inter-Area-Prefix TLV and External-Prefix TLV. Given that Intra-Area-Prefix TLV now has 24 bits metric as well, it would make sense to define the LSInfinity as unreachable for Intra-Area-Prefix TLV as well. Would anyone object such a clarification in RFC8362? thanks, Peter _______________________________________________ Lsr mailing list Lsr@ietf.org<mailto:Lsr@ietf.org> https://www.ietf.org/mailman/listinfo/lsr
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