Zhibo,
On 13/10/2022 08:26, Huzhibo wrote:
Hi LSR:
LSInfinity
The metric value indicating that the destination described by an
LSA is unreachable. Used in summary-LSAs and AS-external-LSAs
I want to clarify the meaning of unreachable in LSifinity,
Assume that a node advertise specific route of 1.1.1.1/32, and an aggregate
route 1.1.0.0/16 is configured.
This node should premature aging of the 1.1.1.1/32 LSA.
If this node using LSInfinity metric instead of prematuring aging, route
1.1.1.1/32 is still reachable.
no, it is not.
Peter
Therefore, the "unreachable" described by LSifinity is not really unreachable.
Thanks
Zhibo hu
-----Original Message-----
From: Lsr [mailto:[email protected]] On Behalf Of Peter Psenak
Sent: Wednesday, October 5, 2022 5:32 PM
To: [email protected]
Subject: [Lsr] RFC 8362 and LSInfinity
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
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