Mark Tinka wrote:
So, with hierarchical routing, routing protocols can carry only rough information around destinations, from which, source side can not construct detailed (often purposelessly nested) labels required for MPLS.
But hosts often point default to a clever router. The requirement from the E2E principle is that routers should be dumb and hosts should be clever or the entire system do not. scale reliably.
In this case, such clever router can ever exist only near the destination unless very detailed routing information is flooded all over the network to all the possible sources. A router can't be clever on something, unless it is provided with very detailed information on all the possible destinations, which needs a lot of routing traffic making entire system not to scale. Masataka Ohta