DNS

Question 1

What is DNS?

Answer 1

Domain name system, how to map between IP addresses and “names” like websites

Question 2

DNS services

Answer 2

hostname to IP address translation, host aliasing, mail server ailiasing, load distribution

Question 3

DNS structure

Answer 3

decentralized to make it easier to scale and more resilient to failure, less vulnerable to censorship, easier to handle traffic volume and maintain, tree-like structure with root at top and sub-domains below(.com, org, edu).

Question 4

What are the DNS root name servers?

Answer 4

server that gets contacted by local name server that cannot resolve name, directly answer requests for records in the root zone and return list of authoritative/TopLevelDomain servers otw

Question 5

what are the TLD servers?

Answer 5

after contacting the root name servers, the local DNS resolver queries one of these domains which returns the IP address for the requested domain name, and that address can then be accessed by the requesting host

Question 6

what is a local DNS name server

Answer 6

each ISP has one, when a host makes a DNS query the query is sent to its local DNS server, which acts as a proxy and forwards query into hierarchy

Question 7

DNS caching

Answer 7

once any name server learns mapping, it caches it, but cache entries timeout/disappear after some time. TLD servers are usually cached to avoid always going to the root. If a name host changes IP addresses, change may not be known until the timeout happens.

Question 8

what is zeroconf?

Answer 8

a set of technologies that automatically creates a usable computer network based on the Internet Protocol Suite (TCP/IP) when computers or network peripherals are interconnected. It does not require manual operator intervention or special configuration servers.

Question 9

how does zeroconf assign IP addresses

Answer 9

picks random adresses, checks for dulicates with DAD, if duplicates then reassign and recheck

Question 10

zeroconf hostname resolution

Answer 10

every computer on the local network stores an individual listing of DNS resources and joins the mDNS, hostname picked by the user

Question 11

what is DNS-ServiceDiscovery?

Answer 11

uses three DNS record types to define location, status, type, and capabilities for services: PTR enumerates available service instances, SRV/A resolves specific service instances, and TXT contains additional information