ROUTING QUESTION: PI and PA IP addresses on the same ASN
I am on a particular host which has a global footprint and thousands of physical servers.
It has both PI and PA IP addresses, its own global ASN and also many IP subnets that are allocated to this hosting provider. It does not use any IP address space that is not 'in its name', either through 'Direct Allocation', 'Allocated PA' or 'Legacy'.
Needless to say, its network is multihomed.
According to theory, the routing table for PA ip address spaces are linked to the routing table of its parent, grandparent etc.. in a hierarchical way all the way up to the /8 provider.
Routing tables for PIs are separately 'fed' into routers (needs to be at least /24 or a block of 256 IP address for this to be accepted).
My question is -- suppose I take a PA (provider aggregatable) IP address from this hosting provider, who exactly is the 'provider' in this case? Is it this hosting provider, given that it 'owns' its IPs, has a global network, and is multihomed (gets upstream from a dozen providers at various parts of the globe, though some locations seem to have only one upstream provider.)
Or does this hosting provider's IPs get aggregated by particular ISPs based on the priority given to the upstream connection for that IP in that IPs routing table (based on BGP)?
The reason I'm asking this question is that I'm seeing some difference between PI and PA IPs on this providers' network, even though I would have assumed that since it's such a huge player, it would be its own provider and therefore PA and PI would essentially work the same?
Also, is it true that the only true Legacy spaces (as in PI and all that) are with RIPE and ARIN, and others like APNIC have converted legacy spaces to PAs, for purposes of routing?