Get familiar with TTL

TTL is definitely necessary if you use the Domain Name System. It functions similarly to an expiration date for DNS records. We’ll see its purpose, its application in the DNS, and how long Time-to-Live takes. So, without further ado, let’s get down to business.

TTL Explanation

The time-to-live (TTL) parameter defines how long a data packet will stay alive after being sent across multiple hops. Either in-network memory or in cache memory. The data packet will be terminated when the timer expires or reaches its hop limit. Data packets vary in size, shape, and content, but they all have the same time-to-live. That time should be computed based on how long data packets must stay in a device to complete their missions.

TTL in Domain Name System (DNS)

In DNS (Domain Name System), the TTL (time-to-live) specifies how long a DNS record, such as an A record or an ALIAS record, is valid (in seconds) and how long a nameserver (recursive or secondary DNS server) can hold it in its cache memory. When the TTL hits 0, the DNS record will be erased.

In the case of a recursive DNS server, the DNS client must ask it again and wait for it to run a new DNS query to obtain the record. After that, it will be cached again according to the TTL.

A secondary DNS server must check with the primary DNS server and conduct a zone transfer to update its DNS records. Consequently, it won’t be able to respond to questions about the domain.

How long does TTL last?

TTL is a unit of time that is measured in seconds. 1hour (3600 seconds), 12 hours (43200 seconds), or 24 hours (86400 seconds) are the most common default values. This means that if you relocate a website to a new server or add a unique URL to your server, the new DNS updates will take 1/ 12 or 24 hours to take effect.

If you plan to make DNS updates soon, you’ll want to choose a short TTL number. This is done to help changes on the Internet spread and be recognized more quickly. That is, increase the minimum DNS TTL value from 0 to a positive integer. It should never be set to zero. It isn’t described in the standard and may result in your DNS information being ignored or refused.

Furthermore, the maximum DNS TTL value is 604800. (7 days). Even though there’s no maximal DNS TTL value, numbers greater than 7 days are rounded down to 7 days.

Conclusion

To sum up, the TTL value is a critical component of networking. It restricts the number of hops a data packet can take and prevents packets from traveling indefinitely across the network. It saves a lot of network resources this way.

On the DNS side, it enables improved DNS record management and indicates whether DNS records inside a DNS server are still valid or have been there for an excessive amount of time.

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