In the context of domains, what is a TTL number?

In the context of domains, what is a TTL number?

In the context of domains, TTL stands for Time to Live. It is a numerical value associated with DNS (Domain Name System) records that indicates how long the information can be cached by resolving nameservers or other DNS servers before it should be refreshed from the authoritative DNS server.

When a resolving nameserver retrieves DNS records from an authoritative server in response to a query, it stores those records in its cache for a certain period defined by the TTL value. The TTL value is specified in seconds and is set by the owner of the DNS records.

The purpose of the TTL is to balance the need for efficient DNS resolution and the ability to handle changes or updates to DNS records. A shorter TTL means that resolving nameservers will refresh their cached records more frequently, ensuring they have the most up-to-date information. However, frequent DNS lookups can increase the load on DNS servers and may result in slower response times.

Conversely, a longer TTL reduces the frequency of DNS lookups, improving performance by reducing the number of queries made to authoritative DNS servers. However, longer TTL values also mean that changes to DNS records take longer to propagate across the DNS system and be reflected in resolving nameservers' caches.

TTL values can vary for different types of DNS records within a domain. For example, the TTL for an A record (which maps a domain to an IPv4 address) might be different from the TTL for an MX record (which specifies mail server settings). Each DNS record can have its own TTL value.

DNS administrators or domain owners can configure the TTL value when setting up or updating DNS records. It is important to consider the trade-off between caching duration and the need for timely updates when determining the appropriate TTL for DNS records.