| 1. | What is the difference between iterative and recursive DNS? |
| Answer: | With iterative DNS, the client's DNS server is responsible for determining the IP address associated with a domain. To achieve this, the DNS servers send NS (or referral) records to the client DNS server until it reaches the DNS server authoritative for the requested domain. With recursive DNS, each DNS server in the system is responsible for determining the IP address for the domain, by recursively issuing A record requests until the authoritative DNS server is reached. |
| 2. | What type of answer occurs in this situation: your local DNS server responds to your A record request with a cached copy of the A record? |
| Answer: | When you request an A record, your local DNS server may cache it for the length of time specified in the TTL by the authoritative DNS server. If you request the A record again before the TTL expires, the answer from your local DNS server is called a nonauthoritative answer. |
| 3. | What is the purpose of SOA DNS records? |
| Answer: | SOA records tell a DNS server that it is authoritative for the particular domain. |
| 4. | What are the various DD metrics you can use to select among your available sites? |
| Answer: | You can use random, portion, preference, routing protocol, RTT, and Boomerang metrics to select from your available sites. |
| 5. | What are stateless RTT calculations? |
| Answer: | When the Distributed Director calculates the best RTT between the client's DNS server and the available sites, it does not store the RTT state associated to the requesting client for subsequent DNS queries from that client for the requested domain. |
| 6. | Why should you disable Boomerang when using HTTP redirects with the DD? |
| Answer: | When you use the Boomerang protocol, the client DNS server is the only entity that knows which site has the shortest return path to the client DNS server (based on which A record it receives first from the available sites). Therefore, the DD cannot determine which site to include in the "Location:" header of the HTTP 301 Moved method. |
| 7. | Why is stateful proximity beneficial? |
| Answer: | Use of stateful proximity reduces overall response times by avoiding client DNS server probes for every request. |
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| 8. | Why is stateful DNS-sticky beneficial? |
| Answer: | Stateless DNS-sticky using source IP hashing may provide an uneven distribution of requests across your sites. However, using a stateful GSDB enables you to use intelligent load balancing methods to distribute client requests across your sites, such as the least-loaded and proximity methods. |
