The document discusses the Domain Name System (DNS) which provides a hierarchical namespace and mapping system to translate between domain names and IP addresses on the internet. It describes the domain name space, distribution of the name space using name servers and zones, and how DNS works through resolution of queries and responses using different record types. Examples are given of forward and inverse queries and responses to look up addresses and validate clients.
12. A primary server loads all information from the disk file; the secondary server loads all information from the the primary server. When the primary downloads information from the secondary, it is called zone transfer.
25. Figure 18-16 QR: Query/Response OpCode: 0 standard, 1 inverse, 2 server status AA: Authoritative TC: Truncated RD: Recursion Desired RA: Recursion Available rCode: Status of the error Flags fields
33. Example 1 A resolver sends a query message to a local server to find the IP address for the host “ chal.fhda.edu . ” . We discuss the query and response messages separately.
36. Example 2 An FTP server has received a packet from an FTP client with IP address 153.2.7.9. The FTP server wants to verify that the FTP client is an authorized client.