Gunter, (1) Multiple-ABRs > > > > I was wondering for example if a ingress router receives a PUA signaling > that a given locator becomes unreachable, does that actually really signals > that the SID ‘really’ is unreachable for a router? >
Aas there is no association between node_id (perhaps loopback) and SIDs (note that egress can use many SIDs) UPA really does not signal anything about SIDs reachability or liveness. > For example (simple design to illustrate the corner-case): > > > > ingressPE#1---area#1---ABR#1---area---ABR#2---area#3---egressPE#2 > > | | > > | | > > +--------area#1---ABR#3---area---ABR#4---area#3--------+ > > > > What if ABR#4 would loose connectivity to egressPE#2 and ABR#2 does not? > > In that case ABR#4 will originate a UPA/PUA and ABR#2 does not originate a > PUA/UPA. > > How is ingressPE#1 supposed to handle this situation? The only thing > ingressPE#1 see is that suddenly there is a PUA/UPA but reachability may > not have changed at all and remains perfectly reacheable. > Valid case. But PE1 should only switch when alternative backup path exists. If there is a single path it should do nothing in any case of receiving UPA. We have discussed that case before and as you know the formal answer was "out of scope" or "vendor's secret sauce" :). The justification here is that switching to healthy backup is better then continue using perhaps semi-sick path. Best, R.
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