From 001c5c8a5b6f1b34cb4365545e32a96f48adac71 Mon Sep 17 00:00:00 2001 From: Donne Martin Date: Mon, 27 Feb 2017 05:19:33 -0800 Subject: [PATCH] Add Domain name system section --- README.md | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/README.md b/README.md index 521277d4..efbc4d8e 100644 --- a/README.md +++ b/README.md @@ -653,3 +653,41 @@ This topic is further discussed in the [Database](#database) section: * [Master-slave replication](#master-slave-replication) * [Master-master replication](#master-master-replication) + +## Domain name system + +

+ +
+ Source: DNS security presentation +

+ +A Domain Name System (DNS) translates a domain name such as www.example.com to an IP address. + +DNS is hierarchical, with a few authoritative servers at the top level. Your 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)](https://en.wikipedia.org/wiki/Time_to_live). + +* **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` (example.com to www.example.com) or to an `A` record. + +Services such as [CloudFlare](https://www.cloudflare.com/dns/) and [Route 53](https://aws.amazon.com/route53/) provide managed DNS services. Some DNS services can route traffic through various methods: + +* [Weighted round robin](http://g33kinfo.com/info/archives/2657) + * Prevent traffic from going to servers under maintenance + * Balance between varying cluster sizes + * A/B testing +* Latency-based +* Geolocation-based + +### Disadvantage(s): DNS + +* Accessing a DNS server introduces a slight delay, although mitigated by caching described above. +* DNS server management could be complex, although they are generally managed by [governments, ISPs, and large companies](http://superuser.com/questions/472695/who-controls-the-dns-servers/472729). +* DNS services have recently come under DDoS attack, preventing users from accessing websites such as Twitter without knowing Twitter's IP address(es). + +### Source(s) and further reading + +* [DNS architecture](https://technet.microsoft.com/en-us/library/dd197427(v=ws.10).aspx) +* [Wikipedia](https://en.wikipedia.org/wiki/Domain_Name_System) +* [DNS articles](https://support.dnsimple.com/categories/dns/)