Decoding DNS caching: Potential, pitfalls, alternatives
Learn about DNS caching, its benefits, and limitations, and consider some alternatives for fast content delivery.
By Kelsie Anderson
Let’s face it: The internet is huge, with billions of sites offering seemingly endless options for entertainment and engagement. If you want to hold consumers’ attention, you have to maintain a website that loads quickly and efficiently. The margin of error is measured in seconds. In fact, for every additional second it takes for one of your website pages to load, your conversion rate drops by more than 2%.
Clearly, finding ways to reduce your site’s latency and increase its availability is critical for your bottom line. DNS caching is one tool that can play a significant role in shaping internet interactions, running in the background to ensure your websites load swiftly and seamlessly.
However, while DNS caching is widely touted as a method that can solve many latency issues, it’s not the only option when it comes to improving site performance. In this blog post, we’ll explain what DNS caching is, as well as its benefits and limitations. We’ll also discuss a few DNS caching alternatives—and when it might be time for your organization to look into one.
What is DNS caching?
DNS caching is the process through which a temporary storage area, known as cache, holds DNS query results.
Essentially, when you request a web address, your computer contacts a DNS (Domain Name System) server to resolve the domain name to an IP address. The response is stored locally in the DNS cache. The next time you or someone else on the network requests the same address, the DNS cache supplies the IP address, circumventing the need to contact the DNS server again.
This memory storehouse is the essence of DNS caching.
Benefits of DNS caching
You can think of DNS caching as an attentive concierge at a prestigious hotel who’s always ready to meet guests’ needs and keep their preferences in mind. DNS caching, with its repository of domain name resolutions, plays a similar role in internet browsing.
For businesses looking to enhance their customers’ online experiences, the benefits of DNS caching, which we’ll explore below, make it a difficult tool to pass up.
Accelerated response times
By circumventing the need to contact DNS servers for repeated requests, DNS caching substantially reduces the time it takes for web pages to load. This circumvention results in a more responsive and enjoyable user experience.
Decreased bandwidth usage
The cache reduces the number of queries sent over the network. This reduction leads to decreased bandwidth usage, which can translate into cost savings, especially for organizations with a lot of network traffic.
Mitigated server load
By sending fewer requests, caching alleviates the burden on DNS servers. With fewer queries to address, DNS servers have an enhanced ability to handle incoming traffic, ensuring better performance and reliability.
In instances where a DNS server is momentarily unreachable, DNS caching enables users to access previously fetched information that’s still in the cache.
Where DNS caching falls short
While DNS caching is instrumental in improving website load times and reducing bandwidth usage, it’s not without its drawbacks. Some of the prominent disadvantages of DNS caching include:
One of the most common issues with DNS caching is that the cached data can become outdated. If a website’s IP address changes and the DNS cache hasn't updated, it may direct users to the old IP address, causing services to appear offline and other access issues.
DNS cache poisoning, also known as DNS spoofing, occurs when false information is inserted into the DNS cache. Attackers can exploit this false information to redirect users to malicious websites, thereby posing security risks.
Increased debugging complexity
When dealing with DNS issues, having a cache can complicate debugging. Since the DNS cache may return an old response, it might be unclear whether there’s an issue with the DNS server itself or just outdated information in the cache.
Inefficiency in short-term DNS changes
For administrators who need to make frequent changes to DNS records, caching can be problematic. Changes may not be reflected immediately due to the TTL (Time to Live) values, delaying the propagation of the changes.
If the DNS cache isn’t properly configured, it can end up storing an excessive amount of data. This bloat can lead to inefficient use of resources and, in extreme cases, degrade performance.
Incorrectly configured TTL values
If the TTL values aren’t configured appropriately, it can either cause the cache to store information for too long, leading to stale data, or not long enough, negating the benefits of caching.
Incompatibility with zero downtime deployments
For services that rely on changing DNS records for zero downtime deployments, DNS caching can cause issues. Users might still be directed to old servers that are being decommissioned because their DNS cache hasn’t updated yet.
Negative caching happens when a DNS cache stores the information that a particular DNS record doesn’t exist. If this happens shortly before the record is created, users may be unable to access the new resource until the negative cache expires.
DNS caching alternatives
Fortunately, other options exist that can help network administrators and developers mitigate or eliminate some of the downsides of DNS caching while still reaping its benefits. Alternatives primarily focus on different methods of resolving domain names or optimizing how DNS queries are processed. Below, we’ve described some of the prominent DNS caching alternatives.
Border Gateway Protocol (BGP) Anycast allows multiple geographically dispersed servers to share the same IP address. When a DNS query is made, BGP Anycast routes it to the nearest or most optimal server based on various factors like distance and server health. This distribution ensures optimized performance and enhanced resilience against Distributed Denial of Service (DDoS) attacks.
DNS load balancing
Load balancing distributes DNS requests across several servers. By doing this, you ensure that no single DNS server is overwhelmed with too many requests at once.
GeoDNS routes users to the nearest server based on their geographic location, which is especially useful for global services with users worldwide.
DNS over HTTPS (DoH)
DoH encodes DNS queries as HTTPS traffic, making DNS queries more secure and allowing them to bypass local DNS servers entirely, which can sometimes be faster.
DNS over TLS (DoT)
Similar to DoH, DoT encrypts DNS queries using TLS. It’s focused more strictly on security and ensuring that only the intended recipient can read the DNS queries.
Public DNS servers
Sometimes, using a different DNS server than the one your ISP provides can result in faster resolution times. Public DNS servers like Google DNS, Cloudflare’s 126.96.36.199, and OpenDNS are often used as alternatives.
Prefetching is a technique where the browser proactively performs domain name resolution on links the user may follow, potentially reducing load times for navigating to those links.
Split-horizon DNS allows different IP addresses to be returned depending on the source of the DNS query. It can be used for load balancing or to provide different responses for internal and external queries.
While not a direct alternative, using a reverse proxy or a Content Delivery Network (CDN) can reduce the dependency on DNS resolution by caching content closer to the user, thus potentially reducing the number of DNS lookups required.
When a DNS caching alternative might be right for your business
Selecting the right DNS caching alternative depends on the specific needs and challenges faced by an organization or network. Regardless of which one you use, an alternative might be the fitting choice if any of the reasons below apply to your organization.
You have a global presence
For businesses with a global customer base, DNS caching may not be sufficient to ensure optimal performance. In such cases, using alternatives like BGP Anycast or GeoDNS can direct traffic to the nearest data center, reducing latency and improving user experience.
You have high security requirements
When a business is particularly sensitive to security threats such as DNS cache poisoning, using secure alternatives like DoH or DoT can provide additional security layers.
You need frequent DNS record changes
If a business needs to make frequent changes to DNS records, DNS caching can delay the propagation of these changes. In this scenario, a DNS caching alternative with more rapid update capabilities might be necessary.
You have high availability and scalability requirements
For services that need to be highly available and scalable, relying solely on DNS caching can be insufficient. Implementing load balancing or employing a CDN can help distribute traffic and ensure high availability.
Your compliance and data sovereignty practices are under a microscope
Certain businesses might be subjected to regulatory requirements that dictate how and where data is stored and transferred. Employing specialized DNS solutions that comply with these regulations can be crucial.
You have custom filtering needs
When businesses require specific control over what types of content can be accessed through their networks, DNS filtering solutions can be employed as an alternative to standard DNS caching.
You need access to enhanced performance metrics
Businesses that require detailed analytics and performance metrics to monitor their services may benefit from advanced DNS services that provide insights beyond what traditional DNS caching offers.
You want zero downtime deployments
For services aiming for zero downtime deployments, where DNS records play a critical role, DNS caching might not suffice. Using solutions that allow for instant changes and monitoring can be more effective.
You need to handle DDoS attacks efficiently
If your business is likely to be a target of DDoS attacks, implementing a DNS solution that can handle a large number of requests, such as Anycast DNS, can be vital for maintaining service availability during an attack.
Understanding the specific needs and challenges of your business is crucial in determining whether a DNS caching alternative is necessary. It’s important to analyze your network infrastructure, security requirements, performance needs, and regulatory landscape to make an informed decision.
Experience the benefits of DNS caching—without the downsides—with Telnyx
DNS caching is an indispensable internet component, driving faster responses and reduced server loads. However, it’s crucial to be aware of its limitations. If your organization finds you need a DNS caching alternative, Telnyx Global Edge Router is a powerful option.
Global Edge Router uses BGP Anycast to instantaneously and automatically failover to a new server if one goes offline. That means your services stay online, with no manual intervention required.
For businesses with a global presence, Edge Router leverages our global edge network to route data close to the source, providing an optimal path that can reduce latency, ensure efficient data transmission, and improve overall network performance.
Contact our team of experts to learn how you can overcome the limitations of DNS caching and improve network performance with Global Edge Router.