It is destination based flat routing distributed 100% before any data packet within each layer - yes. But layers are decoupled so in a sense this is what defines a hierarchy overall.
So transport is using MPLS LSPs most often hosts IGP routes are matched with LDP FECs and flooded everywhere in spite of RFC 5283 at least allowing to aggregate IGP.
Then say L2VPNs or L3VPNs with their own choice of routing protocols are in turn distributing reachability for the customer sites. Those are service routes linked to transport by BGP next hop(s).
Many thx,
R.
Robert Raszuk wrote:
> MPLS LDP or L3VPNs was NEVER flow driven.
>
> Since day one till today it was and still is purely destination based.
If information to create labels at or near sources to all the
possible destinations is distributed in advance, may be. But
it is effectively flat routing, or, in extreme cases, flat host
routing.
Or, if information to create labels to all the active destinations
is supplied on demand, it is flow driven.
On day one, Yakov said MPLS had scaled because of nested labels
corresponding to routing hierarchy.
Masataka Ohta