What process occurs when obtaining a DNS answer for ISC.SANS.ORG?

What process occurs when obtaining a DNS answer for ISC.SANS.ORG?

• A. Ask the last cached server for the information
• B. Contact the ISP's DNS server directly
• C. Ask one of 13 root servers, then .ORG, then SANS.ORG's
• D. Request the information from all authoritative servers simultaneously

Answer: (C)

When obtaining a DNS answer for ISC.SANS.ORG, the process follows a hierarchical structure in the Domain Name System (DNS). The correct choice involves querying the DNS by starting at the top of the hierarchy with the root servers. When a client (or resolver) needs to resolve a domain name, it first queries one of the 13 root DNS servers. These root servers do not hold the actual records for domains but can direct the resolver to the appropriate top-level domain (TLD) servers, which in this case is the .ORG servers. After receiving a referral from the root server, the resolver queries the .ORG TLD servers, which then respond with the address of the authoritative name servers for ISC.SANS.ORG. Finally, the resolver queries these authoritative name servers to obtain the actual DNS records for ISC.SANS.ORG. This step-by-step querying process ensures that the resolver finds the correct IP address associated with the domain name by using the structured DNS hierarchy, making option C the accurate depiction of how the DNS resolution occurs. This method is efficient and minimizes the need for redundant queries, as each step provides specific information to locate the next server in the resolution chain.

When obtaining a DNS answer for ISC.SANS.ORG, the process follows a hierarchical structure in the Domain Name System (DNS). The correct choice involves querying the DNS by starting at the top of the hierarchy with the root servers.

When a client (or resolver) needs to resolve a domain name, it first queries one of the 13 root DNS servers. These root servers do not hold the actual records for domains but can direct the resolver to the appropriate top-level domain (TLD) servers, which in this case is the .ORG servers. After receiving a referral from the root server, the resolver queries the .ORG TLD servers, which then respond with the address of the authoritative name servers for ISC.SANS.ORG. Finally, the resolver queries these authoritative name servers to obtain the actual DNS records for ISC.SANS.ORG.

This step-by-step querying process ensures that the resolver finds the correct IP address associated with the domain name by using the structured DNS hierarchy, making option C the accurate depiction of how the DNS resolution occurs. This method is efficient and minimizes the need for redundant queries, as each step provides specific information to locate the next server in the resolution chain.