DNS Quiz: Prepare with DNS Exam Questions

Domain Name System: A Summary

The Domain Name System (DNS) is a naming system for computers, services, and other resources in the Internet or other IP networks.
DNS translates domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols.
DNS has been an essential component of the functionality of the Internet since 1985.
DNS delegates the responsibility of assigning domain names and mapping those names to Internet resources by designating authoritative name servers for each domain.
The DNS protocol is a detailed specification of the data structures and data communication exchanges used in the DNS, as part of the Internet protocol suite.
DNS maintains the domain name hierarchy and provides translation services between it and the address spaces.
DNS name servers store the DNS records for a domain and respond to queries against its database.
The most common types of records stored in the DNS database are for start of authority (SOA), IP addresses (A and AAAA), SMTP mail exchangers (MX), name servers (NS), pointers for reverse DNS lookups (PTR), and domain name aliases (CNAME).
DNS has been expanded over time to store records for other types of data for either automatic lookups, such as DNSSEC records, or for human queries such as responsible person (RP) records.
DNS reflects the structure of administrative responsibility on the Internet, with each subdomain being a zone of administrative autonomy delegated to a manager.
DNS uses a distributed database system, which uses the client-server model, with each domain having at least one authoritative DNS server that publishes information about that domain and the name servers of any domains subordinate to it.
DNS cache servers store DNS query results for a period of time determined in the configuration (time-to-live) of the domain name record in question, improving efficiency, reducing DNS traffic across the Internet, and increasing performance in end-user applications.Summary of Domain Name System
DNS caching and recursive functions can be implemented independently in servers for special purposes.
ISPs provide recursive and caching name servers for their customers, and home networking routers implement DNS caches and recursion to improve efficiency in the local network.
The client side of the DNS is called a DNS resolver, which initiates and sequences queries for full resolution of the resource sought.
DNS resolvers are classified by query methods, such as recursive, non-recursive, and iterative.
A non-recursive query provides a record for which the server is authoritative or provides a partial result without querying other servers.
A recursive query queries a single DNS server, which may query other DNS servers on behalf of the requester.
Iterative query procedure is a process in which a DNS resolver queries a chain of one or more DNS servers.
A circular dependency occurs when a name server in delegations is identified by name rather than IP address.
DNS caching reduces the load on DNS servers by caching results locally or in intermediate resolver hosts.
Reverse DNS lookup is a query of DNS for domain names when the IP address is known.
DNS message format uses two types of DNS messages, queries and replies, with a header and four sections: question, answer, authority, and an additional space.
DNS supports wildcard DNS records which specify names that start with the asterisk label.The Domain Name System (DNS)
DNS is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network.
DNS translates domain names to IP addresses, allowing human-readable domain names to be used instead of IP addresses.
DNS is organized in a hierarchical structure of domains, with the root domain at the top.
DNS uses Resource Records (RR) to store information about a domain name, including the IP address of the server that hosts the domain's website.
DNS employs caching to reduce the traffic on the network and speed up responses to queries.
DNS uses different types of queries, including recursive and iterative queries, to resolve domain names.
DNS has security issues, such as DNS cache poisoning and the IDN homograph attack.
DNS has privacy issues, with user queries and nameserver responses being sent unencrypted.
DNS uses domain name registrars, which are accredited by ICANN or other organizations, to delegate the right to use a domain name.
DNS is defined by Request for Comments (RFC) documents published by the Internet Engineering Task Force (IETF).
DNS has undergone protocol extensions, including Extension Mechanisms for DNS (EDNS) and support for Dynamic DNS updates.
The original DNS protocol used the User Datagram Protocol (UDP) for transport over IP, but several protocol developments have been made for reliability, security, privacy, and other criteria.