DNS Resolution Process

DNS Resolution

• The process of translating a domain name into an IP address
• Involves a series of queries to DNS servers to resolve the domain name
• Steps:
  1. Browser cache: Check browser cache for the IP address
  2. Operating system cache: Check OS cache for the IP address
  3. Local DNS resolver: Send query to local DNS resolver (e.g. /etc/hosts file)
  4. Recursive DNS server: Send query to recursive DNS server (e.g. ISP's DNS server)
  5. Root DNS server: Send query to root DNS server (e.g. .)
  6. TLD DNS server: Send query to TLD DNS server (e.g. .com)
  7. Authoritative DNS server: Send query to authoritative DNS server (e.g. domain's DNS server)
  8. IP address: Receive IP address from authoritative DNS server

DNS Servers

• Recursive DNS server: Resolves domain names recursively, starting from the root DNS server
• Authoritative DNS server: Holds the DNS records for a specific domain name
• Caching DNS server: Caches DNS records to reduce the load on recursive DNS servers
• Proxy DNS server: Acts as an intermediary between clients and DNS servers
• DNS forwarder: Forwards DNS queries to another DNS server

DNS Records

• A record: Maps a domain name to an IP address
• AAAA record: Maps a domain name to an IPv6 address
• CNAME record: Maps an alias or alternate name to a canonical name
• MX record: Maps a domain name to a mail server
• NS record: Maps a domain name to a name server
• PTR record: Maps an IP address to a domain name (reverse DNS)
• SOA record: Specifies the start of authority for a DNS zone
• TXT record: Holds text information about a domain
• SRV record: Maps a service name and protocol to a domain name and port number

DNS Security

• DNS spoofing: Attack where a fake DNS server returns a fake IP address
• DNS cache poisoning: Attack where a fake DNS record is injected into a DNS cache
• DDoS attacks: Attack where a large volume of DNS queries are sent to overwhelm a DNS server
• DNSSEC: A security protocol that authenticates DNS data and ensures its integrity
• TLS/SSL certificates: Used to encrypt DNS traffic and ensure authenticity

DNS Cache

• Browser cache: Stores DNS records in the browser's cache
• Operating system cache: Stores DNS records in the OS's cache
• DNS cache server: Stores DNS records to reduce the load on recursive DNS servers
• TTL (Time To Live): Specifies how long a DNS record is cached
• Cache poisoning: Attack where a fake DNS record is injected into a DNS cache

DNS Resolution

• Translates a domain name into an IP address through a series of queries to DNS servers
• Involves 8 steps: browser cache, OS cache, local DNS resolver, recursive DNS server, root DNS server, TLD DNS server, authoritative DNS server, and receiving the IP address

DNS Servers

• Recursive DNS server: Recursively resolves domain names starting from the root DNS server
• Authoritative DNS server: Holds DNS records for a specific domain name
• Caching DNS server: Caches DNS records to reduce load on recursive DNS servers
• Proxy DNS server: Acts as an intermediary between clients and DNS servers
• DNS forwarder: Forwards DNS queries to another DNS server

DNS Records

• A record: Maps a domain name to an IP address
• AAAA record: Maps a domain name to an IPv6 address
• CNAME record: Maps an alias or alternate name to a canonical name
• MX record: Maps a domain name to a mail server
• NS record: Maps a domain name to a name server
• PTR record: Maps an IP address to a domain name (reverse DNS)
• SOA record: Specifies the start of authority for a DNS zone
• TXT record: Holds text information about a domain
• SRV record: Maps a service name and protocol to a domain name and port number

DNS Security

• DNS spoofing: Attack where a fake DNS server returns a fake IP address
• DNS cache poisoning: Attack where a fake DNS record is injected into a DNS cache
• DDoS attacks: Attack where a large volume of DNS queries are sent to overwhelm a DNS server
• DNSSEC: A security protocol that authenticates DNS data and ensures its integrity
• TLS/SSL certificates: Used to encrypt DNS traffic and ensure authenticity

DNS Cache

• Browser cache: Stores DNS records in the browser's cache
• Operating system cache: Stores DNS records in the OS's cache
• DNS cache server: Stores DNS records to reduce load on recursive DNS servers
• TTL (Time To Live): Specifies how long a DNS record is cached
• Cache poisoning: Attack where a fake DNS record is injected into a DNS cache

DNS Resolution

• DNS resolution involves translating a domain name into an IP address through a series of requests and responses between DNS clients, resolvers, and DNS servers
• The process occurs in three stages: recursive resolution, authoritative resolution, and cache resolution

DNS Resolution Stages

• Recursive resolution: A DNS client queries a recursive DNS resolver, which then queries other DNS servers to resolve the domain name
• Authoritative resolution: The recursive resolver receives the IP address from an authoritative DNS server, responsible for the domain name
• Cache resolution: The recursive resolver caches the resolved IP address to speed up future requests

DNS Servers

• Recursive DNS servers (caching DNS servers) cache DNS records to speed up resolution
• Authoritative DNS servers are responsible for specific domain names and provide actual DNS records
• Root DNS servers are the highest level, responsible for the root zone (.) and delegating requests to top-level domain (TLD) servers
• TLD DNS servers are responsible for specific TLDs (e.g., .com, .org)

DNS Records

• A record: Maps a domain name to an IP address
• CNAME record: Maps an alias or alternate name to a canonical name of a server or host
• MX record: Maps a domain name to a mail server
• NS record: Maps a domain name to a name server
• PTR record: Maps an IP address to a domain name (reverse DNS)
• TXT record: Holds text information about a domain
• SOA record: Specifies the start of authority for a DNS zone

DNS Security Threats

• DNS spoofing: Attackers intercept DNS queries and return fake DNS records
• DNS cache poisoning: Attackers inject fake DNS records into a cache to redirect users to malicious sites
• DNS amplification attacks: Attackers use DNS servers to amplify traffic in a DDoS attack

DNS Security Measures

• DNSSEC: A security protocol that uses digital signatures to authenticate DNS records and prevent spoofing

DNS Cache

• Browser cache: Web browsers cache DNS records to speed up page loading
• Operating system cache: The operating system caches DNS records to speed up DNS resolution
• DNS resolver cache: Recursive DNS resolvers cache DNS records to speed up resolution
• Time to live (TTL): The time period for which a DNS record is valid in the cache
• Cache invalidation: The process of updating or removing cached DNS records when they expire or change

Learn the steps involved in translating a domain name into an IP address, from browser cache to root DNS servers.