Tuesday 4 January 2022
Domain Name System
A Domain Name System (DNS) translates a domain name such as www.google.com to an IP address.
DNS is hierarchical, with a few authoritative servers at the top level.
Router or ISP provides information about which DNS server(s) to contact when doing a lookup. Lower level DNS servers cache mappings, which could become stale due to DNS propagation delays. DNS results can also be cached by your browser or OS for a certain period of time, determined by the time to live (TTL).
- NS record (name server) - Specifies the DNS servers for your domain/subdomain.
- MX record (mail exchange) - Specifies the mail servers for accepting messages.
- A record (address) - Points a name to an IP address.
- CNAME (canonical) - Points a name to another name or
CNAME(google.com to www.google.com) or to anArecord.
Services such as CloudFlare and Route 53 provide managed DNS services. Some DNS services can route traffic through various methods:
- Weighted round robin
- Prevent traffic from going to servers under maintenance
- Balance between varying cluster sizes
- A/B testing
- Latency-based
- Geolocation-based
References:
https://github.com/donnemartin/system-design-primer#latency-vs-throughput
