I have a network with 7600 and 10720s in one OSPF Area. ABR is 7600 and all 10720s are internal routers. The DR is one of the 10720s. So let us say now 7600 sends an LSA update to this area. As it is a non-DR it will send to 18.104.22.168. Now the DR will pick up the update and send to other non-DR routers using 22.214.171.124.
Now I would like to know how ACK will work? The acknowledgement from non-DR will be send on 126.96.36.199 and will the DR router in turn send the ACK back to originating router on 188.8.131.52? Or will the originating router get ACK directly from Non-DR routers? What will be the approximate delay if it has to wait for ACK from DR routers? I am asking this as I can see some retransmissions happening in this area..the retransmissions are unicast..