Some Basics You Should Know about TTL (Time to Live)

What Is TTL

Time to Live (TTL) refers to a mechanism that can limit the lifespan or lifetime of data in a computer or network. Given to that fact, TTL is also called hop limit. While in the context of CDNs, TTL mainly indicates the content caching, which is the process of saving a duplicate of your website resources on CND proxies.

-image from keycdn.com

By doing so, the page load speed will be accelerated and the origin server bandwidth consumption will be reduced. TTL manages the refresh rate of these duplicates to make sure that stale versions of your content aren’t served to website visitors.

TTL is an 8-bit field under the Internet Protocol, while it is the 9^th octet of 20 in the IPv4 header. In the IPv6 header, it is the 8^th octet of 44. The highest value of TTL can reach up to 255, which is the maximum value of a single octet.

What is TTL meaning? The above description has already told you that. What’s the working principle of TTL? To get the answer and find more information about TTL, please keep reading this post of MiniTool.

How Does TTL Work

When information packets are created and sent over the Internet, they may continue to pass between routers indefinitely. To alleviate this possibility, data packets are designed with an expiration time called time to live or hop limit.

Packet TTL can be used to decide how long the packet has been in circulation and allow the sender to receive information about the packet path through the Internet. Each packet has a location to store the value that determines how long the data packet should continue to work in the network.

Each time the router receives a data packet, it decrements the TTL count by one, and then passes it to the next location in the network. If the TTL count is equal to zero at any time after the subscription, the router will discard the packet and send the ICMP message back to the original host. The frequently used network commands like ping and traceroute utilize TTL.

When using traceroute command, a series of packets with a higher and higher remaining count of TTL will be sent to the destination via the Internet. Since each step of the connection is the last stop of one of the packets, each location will return an ICMP message to the sender after dropping the packet.

Then the time spent for returning IMCP message to the sender can be used to decide the time to reach each continuous hop on the network.

Related article: ICMP (Internet Control Message Protocol): Definition, Application

The Use of TTL

In addition to tracking router packets on the Internet, time to live (TTL) is also used to store information. Some networks run in a traditional way rather than measuring the hop time between routers.

CDN like Cloudflare CDN usually uses TTL to decide how long the cached content should be served from the CDN edge server before obtaining the new copy from the source websites. By properly setting the amount of time between source site acquisitions, CDN can provide updated content without the need to send the requests to the source sites continuously.

This kind of optimization enables you to efficiently provides content for your customer in a closer location and reduces required bandwidth from the source sites at the same time. In the DNS recording environment, TTL is a value that determines how long the DNS cache server can server DNS records before connecting to an authoritative DNS server and obtaining a new copy of the record.

You may also like this: What Is Internet Protocol Suite and What It Mainly Contains

Bottom Line

What is TTL? What does TTL mean? Read here, you may obtain the answers. Actually, you can will have an overall understanding of TTL like its working principle and use after reading the post.