I got it. Thanks for your explanation.
Thanks Yuanlin -------------------------------------------------------------------- [email protected] 写于 2009-05-20 16:19:17: > [As an individual and co-author] > > >> In the section 5.3, "PCE Discovery", you said "Mechanisms > >> that rely on advertising or querying PCE locations across > >> domains or provider boundaries are undesirable.". > >> > >> I want to know why it is an "undesirable" way. > >> > > > > For the record, we has in the WG, long discussion on whether > > we should advertise PCE across domains using for example BGP > > for that matter. > > There was a good consensus not to, considering the limited > > number of interconnected domains. The advantage was limited > > and introduces other issues (security) ... > > Right. I recall that discussion. > > And the situation with hierarchical PCE is worse. > > Consider, a child PCE in domain-A does not know where the Parent PCE is. It > could be in *any* domain. In order to make contact with the parent PCE, the > child must either know where the parent is (configuration as recommended in > the I-D), or advertise itself across *all* domains. That is, for > child-advertisement to work, every PCE in the network must broadcast an > advertisement to every other node in every other domain in the whole > network. This is "undesirable". > > Alternatively, consider a parent PCE that wants to contact the PCEs in each > of domain-A, B, ..., Z. It could be configured (as recommended in this I-D) > or it must send a broadcast query message to every node in each domain. > Since there is no domain address aggregation(CIDR being just a dream) the > parent PCE must broadcast to every node in the entire network. This is > "undesirable". > > That is, both approaches to discovery are simply not scalable, and would > probably be filtered out at domain boundaries anyway. > > With hierarchical PCE, we are looking at a peering relationship that is > certainly administrative and probably commercial. Such relationships involve > a lot of configuration and negotiation. Adding the configuration of > parent/child PCE locations is an almost trivial addition. > > Cheers, > Adrian > > > _______________________________________________ > Pce mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/pce
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