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Regarding Iterative and Recursive DNS Queries: Which Two of the Following Statements Are Correct?
DNS (Domain Name System) is a crucial component of the internet that translates domain names into IP addresses, allowing users to access websites by typing in familiar URLs. When a user enters a domain name into their web browser, the DNS system is responsible for finding the corresponding IP address associated with that domain. This process involves both iterative and recursive queries. In this article, we will discuss these types of DNS queries and clarify two statements related to them.
Iterative DNS Queries:
1. Statement: Iterative DNS queries involve the DNS resolver querying multiple DNS servers until it finds the authoritative server that can provide the IP address for the requested domain.
Explanation: This statement is correct. During an iterative DNS query, the DNS resolver makes a request to a DNS server, which may not have the IP address information for the requested domain. In response, the DNS server provides a referral to another DNS server that might have the answer. The resolver then repeats the process with the referred server until it reaches the authoritative server that can provide the IP address.
2. Statement: Iterative DNS queries place the burden of finding the IP address on the DNS resolver.
Explanation: This statement is correct. In iterative DNS queries, the DNS resolver is responsible for contacting multiple DNS servers and following the referrals until it reaches the authoritative server. The burden of finding the IP address lies on the resolver as it performs the iterative process.
Recursive DNS Queries:
1. Statement: Recursive DNS queries involve the DNS resolver requesting the IP address from a DNS server, which then performs all necessary steps to find the answer and provides it to the resolver.
Explanation: This statement is correct. In a recursive DNS query, the resolver sends a query to a DNS server and expects a complete answer without having to perform any further steps. The DNS server, upon receiving the query, performs all necessary iterative queries to find the IP address and returns the answer to the resolver.
2. Statement: Recursive DNS queries always require the involvement of the authoritative DNS server.
Explanation: This statement is incorrect. Recursive DNS queries do not always require the involvement of the authoritative DNS server. The recursive query is initially sent to a DNS server, which may be a caching server or a forwarder. If the server has the answer in its cache, it can provide a response without involving the authoritative server. However, if the server does not have the answer, it will perform iterative queries to find the IP address from the authoritative server.
FAQs:
Q1. What is the purpose of iterative DNS queries?
Iterative DNS queries are conducted by the DNS resolver to find the authoritative server that can provide the IP address for a requested domain. It involves querying multiple DNS servers and following referrals until the authoritative server is reached.
Q2. How do recursive DNS queries differ from iterative queries?
Recursive DNS queries involve the DNS server performing all necessary steps to find the IP address and providing a complete answer to the resolver. In contrast, iterative DNS queries require the resolver to contact multiple DNS servers and follow referrals until the authoritative server is found.
Q3. Are recursive DNS queries slower than iterative queries?
Recursive DNS queries may take longer to complete than iterative queries since they involve the DNS server performing additional steps to find the answer. However, this delay is often negligible due to the caching mechanisms employed by DNS servers.
Q4. Can I choose between iterative and recursive DNS queries?
As a user, you do not have control over the type of DNS query used. The DNS resolver and server determine whether to use iterative or recursive queries based on the configuration and requirements of the DNS infrastructure.
In conclusion, the correct statements regarding iterative and recursive DNS queries are that iterative queries involve the resolver querying multiple DNS servers until it finds the authoritative server, and recursive queries involve the resolver requesting the IP address from a DNS server that performs all necessary steps to find the answer. Understanding the differences between these query types is essential for comprehending the DNS resolution process.
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