DRs and BDRs are not necessarily one-to-one with Areas. I think this is the key point to answer your question. DRs and BDRs are the result of the OSPF network type defined on a Router’s interface, not because of some requirement of an Area to have them. OSPF recognizes the following network types:
- Point to Multipoint (Broadcast)
- Point to Multipoint (Non-Broadcast)
- Point to Point
Out of all of those possibilities, only Broadcast and Non-Broadcast form DRs and BDRs. The Broadcast and Non-Broadcast network types describe a multi-access network media, such as Ethernet. In this case OSPF requires that all routers on the same network segment have direct reachability both to the DR and BDR, otherwise the network will break. While reachability to the DR and BDR is required, reachability between DROthers is not.
An OSPF Area might have zero, one, or more than one DR–it all comes down to what type of networks there are and how many in your Area. Below is the output on a router that connects together two different Ethernet segments, all in the same Area:
Neighbor ID Pri State Dead Time Address Interface
0.0.0.2 1 FULL/DROTHER 00:00:35 10.1.1.2 FastEthernet0/1
184.108.40.206 1 FULL/DR 00:00:34 10.1.1.1 FastEthernet0/1
0.0.0.1 1 FULL/BDR 00:00:35 10.0.0.1 FastEthernet0/0
0.0.0.2 1 FULL/DR 00:00:39 10.0.0.2 FastEthernet0/0
See how there are multiple DRs? Each Ethernet segment would have its own DR and BDR election. Therefore, there is no need to pass Type 2 LSAs through another router. In fact, that couldn’t happen anyway, because the multicast addresses, both 220.127.116.11 (all routers) and 18.104.22.168 (all DR/BDR) have a “link-local” scope, where their TTL is set to 1, so the packet would be discarded beyond the local segment. I have attached a Wireshark capture as an example.