How to Test DNS Servers: DNS Performance and Response Time Tests

What is DNS?

Before diving into how to test DNS servers, let’s first discuss what DNS is and how it works.  DNS stands for Domain Name System. It is used to translate domain names from their human-readable form (e.g. google.com) to machine-readable numeric values known as IP addresses (e.g. 142.250.217.78). Every website and device on the internet requires a unique IP address in order to communicate, so DNS servers play an important role in internet functionality.  But DNS is just one component of a greater set of network services called DDI that enable communication over IP-based networks.

DDI is a collective term for the integration of DNS (Domain Name Services), DHCP (Dynamic Host Configuration Protocol), and IPAM (IP Address Management). 

DHCP is the system that dynamically assigns IP addresses within a network, IPAM is a method for tracking and managing the IP address space on a network, and DNS essentially acts as a phone book that keeps a record of all existing IP addresses and manages the mapping between domain names and numbers.

How does DNS Work?

When you type in a domain name or URL to your web browser, the DNS server translates that request into an IP address. This request is known as a query. It enables the machine to connect you to the correct remote host and serve up the corresponding webpage.

  1. A user types a web domain name into the address bar of a browser.
  2. The browser sends a DNS query to its local DNS server also known as a recursive DNS server, or DNS resolver.
  3. If the recursive DNS server already has a response to the domain request stored in its cache, it will return the IP address and the web browser will display the page.
  4. If the recursive DNS server does not have the query response cached, it will forward the request through the hierarchy of authoritative DNS servers to find the corresponding IP address before the webpage will load – this still only takes a fraction of a second.

The recursive server caches a record with the IP address for each domain name so that it can respond directly next time, without contacting other servers. Recursive DNS servers are used locally to lighten the load of authoritative DNS servers because the sheer number of requests would be impossible to handle otherwise. Consider how many people are using the internet at any given time.

This is why testing DNS servers at a high scale is critical to avoid performance bottlenecks or crashes. Read on below to learn more about DNS testing.

DNS Testing: How to Test the Performance of DNS Servers

DNS servers are hit with thousands or even millions of queries per second and need to send responses just as quickly. To performance test DNS servers and ensure they can handle the massive load, organizations should use a high scale DNS testing device to generate millions of unique queries per second and validate whether the servers are responding appropriately and in good time. Don’t hesitate to reach out if you have any questions about DNS response time tests or the other products that we offer.

Domain NameHost IP AddressIP Address AnswerRequest TypeValidated
Google.com110.110.110.10142.250.217.78AAAAY
Youtube.com110.110.110.11208.65.153.238PTRN
Apposite-tech.com110.110.110.12151.101.66.159CNAMEY
Yelp.com110.110.110.13 185.49.81.1SRVN

There are many different types of DNS queries, the most common are listed below.

DNS Request Types:

  • A (IPv4)
  • AAAA (IPv6)
  • PTR (Domain Name pointer)
  • NS (An authoritative name server)
  • MX (A mail exchange)
  • TXT (text strings)
  • SRV (Service Record)
  • NAPTR (Naming authority pointer)
  • CNAME (Domain Name Alias)

And there are also a variety of DNS response codes the server can return, a few of which are listed below.

DNS Response Codes:

  • No Error
  • Format Error
  • Server Failure
  • Non-Existent Domain
  • Not Implemented
  • Query Refused

To thoroughly test the performance and capacity of DNS servers, both valid and invalid requests need to be sent.  Invalid queries induce cache misses and further stress test the DNS server.

By creating and maintaining a master list of the world’s URLs, DNS testing tools can measure the server’s real-world response to both valid and invalid queries.   A good DNS test device will be able to assess queries sent, completed, and lost, track response codes, and measure latency in query response time.  These metrics will provide a clear indication of DNS server performance and give engineers the information they need to optimize the DNS server or deploy more if necessary.

Contact Apposite today to learn more about our DNS testing solutions for carrier-grade DNS servers.

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