Domain Name System (DNS)

What is DNS?

• The Domain Name System
• The mechanism by which internet software translate name to attributes such as addresses
• A globally distributed, stateless, scalable, reliable database
stateless: no authentication needed

DNS ComponentsDNS is comprised of three components

• • Name space (TLDs)

  *what is TLDs? 
  {% blockquote Seth Godin https://en.wikipedia.org/wiki/Top-level_domain  %}
  		 Top level Domain
  		{% endblockquote %}
  

• • Name Servers
• • Resolvers

Why DNS?

• •Human-friendly
• •Is this easy to remember -https://216.58.219.196 ?
• •How about this -https://www.google.com?•De-centralized Administration
• *Elastic IP Address? tom
• De-centralized Administration

Global Distribution

• •Data is maintained locally, but retrievable globally
• •No single server has all the DNS data
• •Remote DNS data is locally cacheable to improve performance

Loose Coherency

• •Each version of a subnet of the database (a zone) has a serial number which is incremented on each database change
• •Changes to the master copy of the database are propagated to replicas
• •Cached data expires according to the timeout set (TTL)

Scalability

• •No limit on the size of the database
• •No limit to the number of queries
• •Queries distributed among masters, slaves, and caches

Reliability•Data is replicated

• •Client can query master or any of the slave servers
• •Client will typically query local caches