Skip to content

Latest commit

 

History

History
135 lines (118 loc) · 7.16 KB

006-DNS-Introduction.md

File metadata and controls

135 lines (118 loc) · 7.16 KB

DNS

Glossary

  • A DNS Service is responsible for managing the DNS records associated with a domain name
  • Domain Registrar
    A Domain Registrar is a company or service where we can purchase or register domain names typically by paying annual charges (e.g., GoDaddy, Amazon Registrar Inc., ...). A domain registrar is a company accredited to register and manage domain names. They act as an intermediary between us and the registries that control top-level domains (TLDs) like .com, .org, and .net. When we want a domain name, we go through a registrar. They handle the registration process and currently, practically all Domain Registrar companies allow us to manage our domain's settings (like DNS records) and ensure our domain remains active as long as we renew it. It means that currently all the domain registrars companies are also offering DNS services.
  • Currently, the Domain Registrar usually provides you with a DNS service to manage your DNS records. Samples are: Amazon Route 53, GoDaddy, ...
  • Zone file: A zone file is a text file that contains the DNS records for a domain; the records are hosted on DNS servers and are essential for the proper functioning of the DNS system, enabling the translation of human-readable domain names into IP addresses.
  • DNS record: DNS records are the individual entries in the zone file. Each record contains specific information about a domain. DNS records provide the necessary mapping between domain names and the underlying infrastructure, enabling us to easily access websites and online services. It is a piece of information stored in the DNS system that maps domain names (like example.com) to specific resources or services, such as IP addresses or email servers. These records guide web traffic and other communications to the right destination on the internet. The DNS records are stored in authoritative DNS servers and are queried whenever someone tries to access a domain.
  • Name Server: resolves DNS queries (Authoritative or Non-Authoritative)
  • Top Level Domain (TLD): .com, .us, .in, .gov, .org, ...
  • Second Level Domain (SLD): amazon.com, google.com, ...

Introduction

  • Domain Name System (DNS) is a decentralized system that translates human-readable domain names (like www.example.com) into IP addresses.

  • The anatomy of domain name: tenant.api.leadmgm.com. DNS uses hierarchical naming structure:\

    .com 
example.com 
www.example.com
api.example.com

  • The RFC explains the anatomy as a syntax RFC-1034

Zone file

  • A zone file is a text file that contains the DNS records for a domain; the records are hosted on DNS servers and are essential for the proper functioning of the DNS system, enabling the translation of human-readable domain names into IP addresses:

DNS records we must know

TTL (time to live)

  • Indicates the Time to Live (TTL) value, or the time (in seconds) a system can cache the current record before needing to refresh it from the DNS server.

A record

  • A Record (Address Record): maps a domain or subdomain to an IPv4 address.
    google.com. 300 IN A 142.250.150.102
    • google.com. represents the domain name.
    • 300 indicates the Time to Live (TTL) value, or the time (in seconds) a system can cache this record before needing to refresh it from the DNS server.
    • IN means the class, which is almost invariably “IN” for internet in this context.
    • A specifies the type of the DNS record – an address record, in this case.
    • 142.250.150.102 is the data element (IPv4) – the actual IP address to which the domain name points.

AAAA record

  • AAAA Record (IPv6 Address Record): similar to A record but for IPv6 addresses. It is the same than A records but with IPv6.
    example.com. 86400 IN AAAA 2001:0db8:85a3:0000:0000:8a2e:0370:7334

CNAME record

  • CNAME (Canonical Name Records): alias of one domain to another (used for subdomains or pointing a domain to another domain). This record works as an alias and maps one name to another. It’s often used to reduce duplication in domain name configurations. It also simplifies the maintenance of multiple records connected to the same IP address. It’s one of the common mechanisms that’s been adopted by cloud services to provision customer-specific services. if we run this command line:
    bash --> dig +noall +answer CNAME blog.mozilla.com, then we obtain:
    blog.mozilla.com. 60 IN CNAME mozilla.wpengine.com.
    it means:

    • blog.mozilla.com. is the new hostname or alias
    • 60 is the (TTL) (time to live)
    • IN is the class
    • CNAME is the type
    • mozilla.wpengine.com. is the existing one commonly called target.

  • Example: Shoes & More is an online store that sells a wide variety of footwear products and accessories to customers globally. They have experienced significant growth, resulting in high website traffic and the need to optimize their website’s performance and loading speed. The company decided to integrate a CDN to enhance its website’s performance. To achieve this, they signed up for a CND service and they were advised to set up a CNAME record. www.shoesandmore.com. IN CNAME cdn.examplecdn.com.

  • www.shoesandmore.com.: The NEW hostname being mapped (ensure the trailing dot is included for full qualification).

  • IN: Denotes the record class, typically IN (Internet).

  • CNAME: Specifies that this is a CNAME record.

  • cdn.examplecdn.com.: The (current existing) target domain provided by the CDN service (replace with the actual CDN-provided domain).

NS record

  • NS (Name Server): specifies authoritative DNS servers for the domain. Identifies the name servers available to answer queries.

MX record

  • MX (Mail Exchange): points to mail servers responsible for receiving email on behalf of the domain.

  • Sample:
    google.com. 74 IN MX 10 smtp.google.com.
    google.com. 202 IN MX 20 alt1.aspmx.l.google.com.

  • 10, 20 are the priority levels. Lower number belongs to higher priority. It means the highest priority must be for smtp.google.com.

  • smtp.google.com. is the mail server.

  • 74, 202 is the (TTL) (Time To Live). The time (in seconds) a system can cache this record before needing to refresh it from the DNS server.

TXT record

  • TXT (Text Record): holds text information, often used for domain verification or to provide information to external sources.

SOA record

  • SOA (Start of Authority): contains information about the domain & the DNS server responsible for the domain. Indicates the authoritative location for answering queries for your domain. Provides essential parameters for the zone, including primary name server and administrator email address.

How works