Domain registrar/registry

A domain registrar is where you buy your domain name from. They are basically domain resellers. They manage basic information about your domain name such as its creation time, expiry time, domain owner information, its status and most importantly name server records. Name server records are what decide where queries about your domain name should go to. There is also domain registry, which is like a domain wholesaler. When you register a domain name at a registrar, the registrar reserves the domain name through the registry.

DNS service provider

Say you have a website up and a visitor types your domain name in the browser, what happens next? A domain name is mapped to an IP address, which creates an A record for the domain name. And this piece of information is stored in the domain name's name servers. The browser will look up the domain name and see what name servers to query the A record against. Sometimes, the registrar provides free DNS managment service that allows you to use their name servers and set up DNS records directly with them. Other times you may need to use a separate DNS service provider if the domain registrar does not offer such services or you are not happy with it.

DNS records

DNS records contain all the information about your domain name and enables it to perform different services. This informaiton is stored in the domain name's name servers. The common ones are A, MX, SPF, DKIM, CNAME, TXT records. A records maps the domain name to one or more IP addresses. MX records designate where emails for your domain names should go to. SPF records store information about which IP addresses or hostnames are allowed to send emails on the behalf of your domain name.

Dynamic DNS

Your Internet Service Providers (ISP) changes your IP addresses from time to time if you have not subscribed to a static IP address, especially when you restart the router. Dynamic DNS service maps a static domain name to the changing IP address at all times so that even if the IP address has changed, the domain name is always pointing to the same IP address. It is commonly used for running web servers, establishing remote desktop connections as well as set up camera viewing remotely.

DNS propagation time

When a DNS record is modified or newly created, it may take up to 24 hours for the result to expand all over the internet. The time the record goes into effect all over the world is called DNS propagation time. How long this time is depends on how often your ISP refreshes data, how often the registry refreshes the zone and the TTL you set up for the record. TTL is the time period for which servers cache the information for your DNS records. For example, if you set the TTL for a particular record to two hours, servers store the information for that record locally for two hours before retrieving updated information from your authoritative nameserver. Shorter TTL settings make can increase propagation speed.