Application Layer DNS

Question 1

What do devices get assigned

Answer 1

numerical ip addresses

Question 2

What are domain names labels for

Answer 2

these ip addresses

Question 3

What does DNS do

Answer 3

converts domain names into ip adresses

Question 4

What layer does DNS belong to in the OSI model

Answer 4

The application Layer (layer 7)

Question 5

What are the components of the URL

Answer 5

Scheme, Authority (Host, Domain, Port), Path, Query, Fragment.

Question 6

How does DNS map hostnames and IP addresses

Answer 6

One hostname → Multiple IPs (Load balancing).
Multiple hostnames → One IP (Shared hosting).

Question 7

What are the two main requirements of DNS

Answer 7

Scalability and security

Question 8

How is DNS structured hierarchically

Answer 8

Root Servers (.) – Direct traffic to TLD servers.
TLD Servers – Manage .com, .org, .uk, etc.
Authoritative Servers – Store actual domain records.

Question 9

What are the root DNS servers and why are they important

Answer 9

13 logical root servers manage DNS globally.

First point of contact when resolving domain names.

Ensures redundancy & reliability.

Question 10

What are Top Level Domain (TLD) servers

Answer 10

Manage Organizational TLDs (.com, .org, .gov).
Manage Geographical TLDs (.uk, .us, .fr).
Controlled by ICANN.

Question 11

What do Authoritative DNS servers do

Answer 11

Hold the actual DNS records and respond to queries.

Question 12

How does the DNS lookup process work

Answer 12

1. Client sends a query to DNS Resolver.
2. Resolver checks cache (if cached, returns result).
3. If not cached, resolver queries Root DNS Server.
4. Root Server directs to TLD Server (e.g., .com).
5. TLD Server directs to Authoritative Server.
6. Authoritative Server returns the IP address.
7. Resolver caches response for future use.

Question 13

What security issues affect DNS

Answer 13

Cache Poisoning – Fake DNS responses redirect users to malicious sites.

Spoofing & Man-in-the-Middle Attacks – Hackers intercept DNS traffic.

Question 14

What is the solution to DNS security issues

Answer 14

DNSSEC (Domain Name System Security Extensions) – Uses digital signatures to verify DNS responses.

Question 15

How does DNSSEC work?

Answer 15

1. DNS Data is hashed to create a digital fingerprint.
2. Digital Signature is created using a private key.
   3, Signature is attached to DNS response.
3. Client verifies response using public key.