Lecture 8: Intro to DNS Flashcards
What is the Doman Name System (DNS)?
Associates a network address (IPv4 or IPv6) with a domain name
What was used to remember network addresses before DNS?
hosts.txt
What was stored in the hosts.txt file?
The domain with the appropriate IP address
What is the problem with the hosts.txt file?
- It doesn’t scale well
- Users could have mismatched hosts.txt files that resulting in a domain resolved to different IP addresses for different people
What are the properties of DNS?
- Loosely consistent: No strict constraints on consistency between DNS servers
- Decentralized: Uses a network of independent authorities
- Hierarchical: Hierarchy dictates what info DNS servers are responsible for
What are the 3 major hierarchical levels? (highest to lowest)
- Root servers
- Top level domain (TLD) servers
- Authoritative name servers
What are Root Servers
Returning a list of top level domain DNS servers
How many root servers are there world wide?
13
Who managers the root zones of DNS?
Internet Corporation for Assigned Names and
Numbers (ICANN)
What are TLD Servers?
Responsible for pointing the user to the correct lower level DNS server based on top level domain
What is a top level domain?
The bit after the . in a domain name
EX: .com, .net, .ca
What are authoritative DNS servers?
Responsible for actually returning a domain-to-IP address pairing
What is iterative resolution?
Where a client sends out a request to each level of the DNS hierarchy
What is recursive resolution?
We offloaded all that work onto another server, and only fetched the final DNS data for ourselves
What is DNS caching?
Rather than resolve every domain
separately, the results can be stored and returned immediately without performing more DNS requests
