DNS resolution
- 1. Domain Name Resolution Joshua Erdman Digital-Foundation.net
- 2. DNS Background What is a domain name? Familiar, easy to remember names for computers on the Internet (such as internic.net). Correspond to a series of numbers (called Internet Protocol numbers, AKA IP addresses) that serve as routing addresses on the Internet. Domain names are used generally as a convenient way of locating information and reaching others on the Internet.
- 3. DNS Background What does it mean to "register" a domain name? The Internet domain name system (DNS) consists of a directory, organized hierarchically, of all the domain names and their corresponding computers registered to particular companies and persons using the Internet. When you register a domain name, it will be associated with the computer on the Internet you designate during the period the registration is in effect. – Taken from ICANN.com
- 4. So what is DNS Resolution? DNS Resolution is the procedure used to resolve a IP address from a domain name. This is very similar to how we get the phone number of a person we want to contact. It is all based on hierarchy.
- 5. DNS Resolution analogy Looking up a phone number Get the phone book of the right city People are listed by last name Then narrow it down to a first name. It is the phone number that allows you to communicate over the phone, not the person’s name.
- 6. DNS Foundation All computers communicate by addressing each other using IP addresses. So every time you try to connect to a website, or send an e-mail, DNS resolution is occurring. Just like phone numbers, multiple domain names can resolve to the same IP address.
- 7. Domain Names vs. URLs A domain name is contained in a URL. See the examples below. ftp://ftp.company.com/downloads.report.doc http://www.networkclue.com/index. php Protocol Resource or File Hostname Domain Name Fully Qualified Domain Name (FQDN)
- 8. DNS Resolution Scenario 5 components http://www.google.com Business DNS 1.2.3.1 Web Server 1.2.3.4 Internet ISP DNS 3.3.3.1 End User PC GTLD Servers
- 10. WHOIS DB
- 11. GTLD History Internic ICANN Internet Consortium for Assigned Names and Numbers Domain Registrars Godaddy.com Register.com Net Sol
- 12. Registrars Benefits: Price Wars Features (e-mail, web hosting, advertising, etc.) Easier to register domains Problems: Long distance wars ISPs using 1 registrar Customers registering because it is now so simple Registrars Godaddy.com Register.com Net Sol
- 13. IP Address Registration ICANN Internet Consortium for Assigned Names and Numbers IP Registrars ARPNIC Asia Pacific Registry RIPE European Registry ARIN American Registry for Internet Numbers
- 14. Reverse DNS Resolution Reverse DNS Resolution is the procedure used to resolve a domain name from an IP address. Recall: Multiple domain names can resolve to an IP address (just like multiple people can have the same phone number). It is the ISP’s responsibility to maintain reverse DNS tables.
- 15. Reverse DNS Resolution 4 components Internet 4.3.2.1.in-addr.arpa Business DNS 1.2.3.1 Web Server 1.2.3.4 ISP DNS 3.3.3.1 GTLD Servers
- 16. Reverse DNS Resolution How is Reverse DNS this useful? Tracing traffic that goes through Firewalls Documentation E-mail server validation