DDI is the software that gives every device on a large network an address and a name. DDI stands for DNS, DHCP and IPAM, its three parts. Large companies, universities, hospitals and banks use it to run these three services together, from one system.
Every device on a network needs an IP address, a number that other devices use to reach it, such as 10.40.12.85. The three parts of DDI all deal with these numbers.
DHCP, the Dynamic Host Configuration Protocol, hands out addresses. When a phone joins the Wi-Fi, it asks for an address. The DHCP server picks a free address and lends it to the phone for a fixed time, for example 8 hours. This loan is called a lease. When the phone leaves, the address becomes free for another device.
DNS, the Domain Name System, turns names into addresses. People remember names such as results.university.in, not numbers. DNS looks up the name and returns the address.
IPAM, IP address management, is the plan of all the addresses. It records which ranges of addresses belong to which building, floor or purpose, and which device has which address now.
Imagine a university in Bhubaneswar with 18 buildings and about 25,000 devices on its network, counting students' phones. In IPAM, the IT team gives each building its own range of addresses. The hostels get the range from 10.40.0.0 to 10.40.63.255, about 16,000 addresses. On the evening that semester results are announced, 9,000 students open results.university.in within a few minutes. DNS answers every lookup with the address of the load balancer in front of the results site, which spreads the visits across several servers. Next morning, IPAM shows that the hostel range is 90% full. The IT team adds a new range before devices start failing to get an address.
Why buy a DDI product, instead of the free DNS and DHCP software that comes with servers? For one office, the free software is enough. For 25,000 devices across many buildings, mistakes are costly. If two devices are given the same address, both stop working. A wrong DNS record makes an app unreachable for everyone. DDI keeps the three services consistent with each other, and records every change.
DDI has also become a security tool. Almost every connection starts with a DNS lookup, including the connections that malware makes to the attacker's server. So the DDI system can spot and block lookups of dangerous names. This is DNS security. DNS also publishes the records that tell other mail servers which servers may send email in the company's name, as explained in DMARC and email authentication. The address requests themselves arrive through the enterprise switches and Wi-Fi access points.