I teach Web Technologies course at COMSATS University to undergrad students. These are lectures slides prepared for students. I thought to share it with all. Hope you would like it. It contains good enough details about how DNS, Hosting and Domain Registration works.

1. Domain Name System (DNS)
Domain Registration
Website Hosting
Asif Shahzad,
Assistant Professor of Computer Science
COMSATS, Lahore. asifsh7@gmail.com
http://bitspedia.com

2. Understanding DNS
• Maps domain and sub-domains to hosts
• In start, it was a simple text file maintained by the
Network Information Center that mapped names
to IP addresses
• University of Wisconsin developed DNS, a
distributed database for managing domain name
and IP addresses, in 1983.
• As the number of computers or devices
increased, the system was transferred to
hierarchical structure.

3. Understanding DNS

4. • ICANN is responsible for managing and
coordinating the DNS to ensure universal
resolvability
• Caching Name Server: Receives requests for
domains and responds IP address of the domain or
list of authoritative DNS servers which it has
cached when serving earlier users’ requests
• Authoritative Name Server: Either it has host IP
address of the domain being queried or list of
other authoritative servers
Understanding DNS

5. Understanding DNS structure
• The heart of the DNS are, 13 Root Servers, distributed
around the world. (Actually it’s a network of hundreds
of servers, using anycast approach)
• All 13 contain the same vital information
• The root name servers publish the root zone file to
other DNS servers and clients on the Internet. The root
zone file describes where the authoritative servers for
the DNS top-level domains (TLD) are located; in other
words: which server one has to ask for names ending in
one of 267 (September 2007) TLDs, such as ORG, NET,
NL or AU. See: http://www.iana.org/domains/root/db

6. DNS Root Servers

7. DNS “Time To Live”
• TTL controls how long a IP-Host entry can
remain in the DNS server. Its cache timeout.
• If you change a DNS record, resolvers would
continue to resolve original address until the
TTL expires. So its better to set short TTL in
start.
• Wait TTL to expire, before expecting the DNS
records to be fully propagated.

8. Domain Name Registry and Registrar
• A Domain Name Registry is a database of all
domain names and the associated name servers
and registrant information in the top level
domains (TLDs). TLD Registries are operated by
multiple companies, some companies operate
more than one TLD Registry.
• A Domain Name Registrar is an organization or
commercial entity that manages the reservation
of Internet domain names. These are accredited
by ICANN or ccTLD Registry operators.

9. Extensible Provisioning Protocol (EPP)
• The Extensible Provisioning Protocol (EPP) is
a flexible protocol designed for allocating
objects within registries over the Internet.
• The motivation for the creation of EPP was to
create a robust and flexible protocol that
could provide communication
between domain name registries and domain
name registrars.

10. Types of Hosting Servers
• Shared Hosting Server
– Shared between multiple users. No freedom to install new softwares,
or update/stop/restart servers
• Virtual Server Hosting Server
– Its dedicated to each user. User operate it just as it’s a dedicated
computer allocated to him but its all virtual
– On single physical computer, multiple OS are setup, and each OS
instance is assigned to particular user. Some intermediate
virtualization software are used e.g. Xen, etc.
– If you choose VPS, I recommend Linode.com. Its best company, I am
using it for last 4 years almost. They have blazing fast servers and
awesome response time whenever you need to contact support.
• Dedicated Server Hosting Server
– A dedicated server (hardware) is allocated to user. Its cost is higher
than others. But these are more fast and you get full freedom.

11. Hosting Server
• So when a user makes a request for a domain
the host-IP address is returned to the browser
by the nearest DNS server cache
• Then browser sends the web request to
received IP address. The web server must be
running on your configured host. DEMO

12. Registering a Domain Name
• Select a Domain Registrar
• Check domain availability, register it providing
domain owner details
• Configure Name Server for your domain that
contains the host details for the domain or
sub-domains
• See the Name Server of some website using
whois query. DEMO

13. Whois Protocol
• A text based protocol used to query information
about a domain from the Domain Registrar. This
information usual contains:
– When the domain was registered
– When it was updated
– When the domain registration would expire
– What are the domain registrant details
– What are the authoritative Name Servers of domain
• Read Whois RFCs for further details

14. Host Your Website
• Choose a hosting provider. You would get the
IP address host computer
• Open DNS server settings that you used while
registering the domain
• Map your domain and sub-domains to
different hosts (IP Addresses) in DNS Server
• Lets see an already configured domain and its
Name Server settings, see DEMO

15. Virtual Host
• Do you want your web server to serve only a
single domain? Definitely not.
• “Virtual hosting is a method for hosting multiple
domains on a single server (or pool of servers).
• A web server is configured to serve different
domains.
• How your server knows which domain was
requested? The “Host” header contains
requested domain name. Demo or see next slide.

17. Web Server Configuration
• After you registered domain, setup the Name
Server and configured the Name Server with
hosts address for the domain or sub-domains
• Now its time to tell your web-server to
respond web requests for a particular domain.
As a web server may host one or more domain
contents. DEMO