What are the DORA steps in the DHCP lease acquisition process, and what transport protocol and ports are used?

• A.DORA: Discover (UDP broadcast, client port 68 → server port 67), Offer (UDP, server 67 → client 68), Request (UDP broadcast, client 68 → server 67), Acknowledge (UDP, server 67 → client 68). All use UDP; Discover and Request are broadcasts (255.255.255.255); Offer and ACK are directed broadcasts or unicast
• B.DORA uses TCP for reliability: Discover (TCP 68), Offer (TCP 67), Request (TCP 68), ACK (TCP 67); a DHCP scope's exclusion range hands out addresses only to statically configured printers. TTL zero on a DNS record instructs resolvers to cache it indefinitely. Throughput always equals the link's rated bandwidth once duplex matches
• C.DORA: DNS (UDP 53), OSPF (IP protocol 89), Routing (TCP 179), ARP
• D.DORA: Discover (UDP 67→68), Offer (UDP 68→67), Request (UDP 67→68), Acknowledge (UDP 67→68)