Block 3 / Unit 3: Domain Name System

what does DNS records "A" mean?

Address Mapping records - records that hold a host name and its corresponding IPv4 address

what is the process of changing a host name to an IP address referred to as?

DNS resolution.

what is a FQDN?

fully qualified domain name (FQDN) - contains both the hostname and a domain name. It uniquely identifies a host within a DNS hierarchy - complete domain name for a specific computer, or host, on the internet.

what are the parts that FQDN consist of?

host name and domain name. Example: www.indiana.edu www = host name indiane.edu = domain

how many logical root servers are there world wide?

- 13 - indicated by letters A through M - operated by organizations such as Cogent, University of Maryland, U.S. Army Research Lab, etc

what is a DNS resolver?

- a component responsible for checking if the host name is available in local cache, and if not, contacts a series of DNS Name Servers, until eventually it receives the IP of the website or service you are trying to reach. - a server designed to receive DNS queries from web browsers and other applications.

what is DNS records?

- contains all the information on how the server should respond to the request.

what is TLD name server?

- takes the domain name provided in the query and provides the IP of an authoritative name server.

what is the DNS root server?

- the first step in translating human readable host names into IP addresses. - a name server for the root zone of the Domain Name System of the Internet. It directly answers requests for records in the root zone and answers other requests by returning a list of the authoritative name servers for the appropriate top-level domain.

what does propagation refer to in terms of DNS?

- the time it takes for the domain name servers world-wide to be updated and able to access the information. - the time it takes to update the DNS system

what does DNS records "CNAME" mean?

Canonical Name Records - used to create aliases of domain names.

what does DNS records "CERT" mean?

Certificate record - stores encryption certificates such as PKIK, SPKI, PGP, etc.

what does DNS records "AAAA" mean?

IP Version 6 Address records - records that hold a host name and its corresponding IPv6 address.

what IP format does the DNS servers return IPs?

IPv6

what does DNS records "MX" mean?

Mail exchange record - specifies a mail exchange server for the domain name.

what does DNS records "NS" mean?

Name server records - delegates a DNS zone to use a specific Authoritative Name Server.

what does DNS records "PTR" mean?

Reverse-lookup pointer records - used to look up a domain name based on an IP address.

what does DNS records "SRV" mean?

Service location - service location record, like MX but for other, newer protocols.

what is DNS and its purpose?

The Domain Name System (DNS) - converts domain names or host names into IP addresses. - Instead of having to remember a host's IP address, DNS allows you to use a friendly name to access the host. For example, it is easier to remember http://www.cisco.com than 198.133.219.25.

True or False: DNS allows for multiple host names to correspond to a single IP address?

True. - this method can be used for virtual hosting.

what is an authoritative name server?

a DNS server that contains DNS records for the specific domain.

how many name servers are there?

one for each Top Level Domain. i.e .com, .net, .org, etc

what does DNS records "SOA" mean?

state of authority - can store important info about the domain such as the email address of the administrator, when the domain was last updated, and how long the server should wait between refreshes.

what is the last stop in the name server query?

the authoritative name server.

how are authoritative name servers organized?

using DNS Zones